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Water distribution pattern in soils under surface and micro-irrigation systems Khan, Maqsood Ahmad 2001

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WATER DISTRIBUTION PATTERNS IN SOILS UNDER SURFACE AND MICRO-IRRIGATION SYSTEMS By MAQSOOD A H M A D K H A N B. Sc., Agricultural Engineering University of Agriculture Faisalabad, Pakistan, 1989 M S E , Agricultural & Environmental Systems Engineering, U S A 1994 North Carolina A&T State University  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE F A C U L T Y OF G R A D U A T E STUDIES INTERDISCIPLINARY PROGRAM We accept this thesis as conforming to the required standard  The Univ^rsi|y of British Columbia Vancouver, Canada December, 2001 © Maqsood Ahmad Khan, 2001  In  presenting this  requirements British freely that  thesis  f o r an advanced  Columbia, available  permission  I for  agree  i np a r t i a l degree  that  reference  f o r extensive  fulfillment  of  a t The U n i v e r s i t y  the library and study. copying  shall  of  make i t  I further  of this  the  agree  thesis f o r  s c h o l a r l y p u r p o s e s may b e g r a n t e d b y t h e h e a d o f my d e p a r t m e n t or  by h i s  or her representatives.  copying o r p u b l i c a t i o n of this  thesis  I t i s understood for financial  gain  n o t b e a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n .  Individual Interdisciplinary The 6021  Graduate S t u d i e s Department  U n i v e r s i t y o f B r i t i s h Columbia Cecil  Green Park  V a n c o u v e r , BC  Road  V6T 1Z1  Canada  D a t e d : "h*<jiwJ**A..  \£ ZLôÔ \  that shall  The  work  patterns  r e p o r t e d here  i n sandy  loam  and  d e s c r i b e s the water silt  micro-irrigation at different  loam  soils  temperatures  distribution  under  surface  simulating  r e g i o n c o n d i t i o n s s u c h as t h o s e e x p e r i e n c e d i n t h e Province of Pakistan. temperature  Specific  variations  c o n s i d e r a t i o n was  before  and  after  and  the  arid  Balochistan g i v e n to the  irrigation,  the  e l u c i d a t i o n of s p a t i a l d i s t r i b u t i o n of a p p l i e d water i n the r o o t zone, a n d ' t h e  e v a l u a t i o n of a f f e c t s of s o i l  movement w i t h i n t h e r o o t i n g  zone.  studies at three different s o i l are  presented.  were m a i n t a i n e d by was  temperatures  loam s o i l s .  (30,  35,  by  Time  technique at four d i f f e r e n t  four  a n d 40  °C)  wooden b o x e s  3  The o p e r a t i n g t e m p e r a t u r e s  using electric  measured  water  R e s u l t s of a s e r i e s of  Experiments were conducted i n 1 m  w i t h sandy loam and s i l t content  t e m p e r a t u r e on  heat  lamps.  Domain  Soil  moisture  Reflectometry  r o o t i n g depths  simulating  (TDR)  the  root  zone o f o n i o n c r o p . B o t h t h e s o i l s showed d i s t i n g u i s h a b l e changes i n s u b s u r f a c e temperature  prior  water  different  at  temperature temperature irrigation  (40  in  silt  surface  the  were  application  of  temperatures. more  irrigation Subsurface  pronounced  at  higher  °C) as compared t o l o w e r t e m p e r a t u r e s u n d e r  systems.  However,  t h e r e was  t e m p e r a t u r e b e y o n d 15  Temperature loam  after  operating  variations  change i n s o i l soils.  t o and  not  any  under  irrigation  trickle  because  irrigation  trickle  significant  cm d e p t h i n e i t h e r o f  changes were o b s e r v e d t o deeper  soil  both  irrigation  as  soil  depths  compared favors  the to  better  w a t e r r e t e n t i o n i n s o i l s as c o m p a r e d t o s u r f a c e i r r i g a t i o n . Lateral s o i l d e p t h was soils. moisture  s p a t i a l d i s t r i b u t i o n of i r r i g a t i o n water along the s i g n i f i c a n t l y a f f e c t e d by s o i l  At lower temperatures c o n t e n t was  higher temperature  (40  (30  a n d 35  h i g h e r i n top °C) .  The  temperature i n both  °C) p e r c e n t v o l u m e t r i c  layer  (Di)  as  compared  p a t t e r n reversed i n the  to  lower  layers  (D ,  D,  favored  the storage of i r r i g a t i o n  2  systems.  and  3  soil  i n sandy  had a r a p i d  laterally  higher  away  from  higher capillary  loam  decrease the  c o n d u c t i v i t y whereas s i l t in  where  4  operating  water  Nevertheless, the l a t e r a l  w a t e r was d i f f e r e n t loam  D)  under  temperature  both  irrigation  d i s t r i b u t i o n of  irrigation  and s i l t  loam  soils.  Sandy  i n volumetric moisture content  application  source  due  to  higher  loam s o i l w i t h l o w e r c o n d u c t i v i t y and  f o r c e s e x h i b i t e d more g r a d u a l l a t e r a l  decline  t h e v o l u m e t r i c m o i s t u r e c o n t e n t away f r o m t h e p o i n t  source.  One p l a u s i b l e  reason might  be t h a t  the g r a v i t y  forces  have  l i m i t e d e f f e c t on t h e w a t e r movement i n f i n e - t e x t u r a l s o i l s as s i l t  loam where c a p i l l a r y  Contours of s o i l wetted  f o r c e s dominate soil  j u s t below the i r r i g a t i o n for both s o i l s . idealized  experiments. different  source  The  temperature The  even  though  i t was  true  places  within  t h e same  radii  from  in  of temperature  s u r f a c e t e n s i o n and h y d r a u l i c  of wetting  front  f o r both s o i l s  increased  and under  w e t t i n g f r o n t s moved v e r t i c a l l y The  found  some  the point  with  possible  reasons  could  on  the increase  both i r r i g a t i o n  greater  soil in  methods.  a n d l a t e r a l l y more be  of  conductivity.  a n d w i d e r a t 40 °C a s c o m p a r e d t o l o w e r t e m p e r a t u r e s °C).  was  The v o l u m e t r i c m o i s t u r e c o n t e n t w e r e d i f f e r e n t a t  viscosity,  spread  irrigation  maximum  source d i d n o t behave as an  a p p l i c a t i o n p r o b a b l y due t o t h e e f f e c t water  The  source i n m a j o r i t y of the experiments  However, i r r i g a t i o n  point  the differences i n  temperatures.  percent volumetric moisture content a f t e r  such  the flow.  moisture content i d e n t i f i e d  patterns at different  a  deeper  (30 a n d 3 5  conductivity,  p e r m e a b i l i t y , and d i f f u s i v i t y a t h i g h e r temperature.  Page Abstract  i  i  List  o f Tables  v i i  List  of Figures  ix  Acknowledgement  xiv  Dedication  xvi  CHAPTER I 1.1  INTRODUCTION  1  Surface  irrigation  2  1.2 - T r i c k l e  irrigation  4  1.3  Temperature E f f e c t  on S o i l W a t e r Movement  1.4  S o i l M o i s t u r e M e a s u r e m e n t b y Time  6  Domain  Reflectometry  9  1.4.1  History  9  1.4.2  Principles  1.5  Justification  1.6  Objectives  CHAPTER I I  of Operation  o f Study  9 '.  11 13  LITERATURE  REVIEW  14  2.1  Field Plot  Studies  14  2.2  Laboratory  Studies  25  2.3  Mathematical  2.4  K n o w l e d g e Gap  CHAPTER I I I 3.1  Model S t u d i e s  MATERIALS AND METHODS  Design o f Study  49 54 56 56  3.2  P r e - i r r i g a t i o n S o i l Moisture Content  63  3.3  I r r i g a t i o n System  64  3.3.1  Surface I r r i g a t i o n  64  3.3.2  Trickle Irrigation  65  3.3.2.1  Emitters Calibration  65  3.4  Temperature C o n t r o l  66  3.5  Evaporation  66  3.6  S o i l W a t e r Measurement  3.7  S o i l Water D i s t r i b u t i o n 3.7.1  Strategy  71  S o i l Water D i s t r i b u t i o n b y Volume  '.  Balance 3.7.2  3.7.3 3.8  A Physical Understanding  CHAPTER I V  71 of Wetted  Profile  71  W e t t e d F r o n t Movement  72  S o i l W a t e r Measurement 3.8.1  68  Technique  72  TDR S o i l M o i s t u r e P o i n t P r o b e Calibration  73  RESULTS AND DISCUSSIONS  74  4.1  C a l i b r a t i o n o f TDR  74  4.2  S o i l Temperatures  80  4.3  E v a p o r a t i o n Losses  92  4.4  S o i l Water D i s t r i b u t i o n  94  4.4.1  94  Volume B a l a n c e 4.4.1.1  Surface I r r i g a t i o n  94  4.4.1.2  Trickle  4.4.2  Discussion  4.4.3  Irrigation  101 107  S o i l Water c o n t e n t P r o f i l e s  113  4.4.3.1  Surface I r r i g a t i o n  113  4.4.3.2  Trickle  118  4.4.4  Irrigation  Wetting Fronts 4.4.4.1  Surface I r r i g a t i o n  123  4.4.4.1.1 s a n d y l o a m s o i l  123  4.4.4.1.2 S i l t  131  4.4.4.2  CHAPTER V  122  Trickle  loam s o i l  Irrigation  139  4.4.4.2.1 Sandy Loam S o i l  139  4.4.4.2.2 S i l t Loam S o i l  147  SUMMARY AND CONCLUSIONS  155  5.1  Summary  155  5.2  Conclusions  163  5.3  Practical  166  5.4  Recommendations  168  5.5  Suggestions  170  Applications  f o r Future Research  BIBLIOGRAPHY  171  APPENDICES  179  LIST OF TABLES  Table  Page  3.1  Physical characteristics  4.1  Average  of s o i l  types  59  m o i s t u r e c o n t e n t and time d e l a y f o r sandy  loam  soil 4.2  Average  76 moisture content and time d e l a y f o r s i l t  loam  soil 4.3  78  Sandy loam s o i l Before and a f t e r  4.4  Sandy loam s o i l b e f o r e and a f t e r  4.5  Sandy loam s o i l b e f o r e and a f t e r  4.6  Sandy loam s o i l b e f o r e and a f t e r  4.7  sandy  depths,  irrigation  83  temperatures a t d i f f e r e n t  depths,  irrigation  86  temperatures a t d i f f e r e n t  depths,  irrigation  88  loam a n d s i l t  loam s o i l s a t  s u r f a c e and t r i c k l e  systems  Percent of t o t a l in  81  temperatures a t d i f f e r e n t  temperatures under  irrigation  depths,  irrigation  E v a p o r a t i o n from sandy different  4.8  temperatures a t d i f f e r e n t  93  a p p l i e d water s t o r e d i n each  loam s o i l  surface i r r i g a t i o n  at different system  temperatures  depth under 95  4.9  Percent of t o t a l a p p l i e d water s t o r e d i n each in  silt  loam s o i l  at different  temperatures  depth  under  s u r f a c e i r r i g a t i o n system 4.10  Percent of t o t a l a p p l i e d water s t o r e d i n each in  sandy loam s o i l  trickle 4.11  98  at different  temperatures  under  i r r i g a t i o n system  102  Percent of t o t a l a p p l i e d water s t o r e d i n each in  silt  trickle  depth  loam s o i l  at different  i r r i g a t i o n system  temperatures  depth  under 105  LIST OF FIGURES  Figure  Page  3.1  T y p i c a l Root d i s t r i b u t i o n a l o n g t h e R o o t i n g Depth  ..  3.2  E x p e r i m e n t a l Setup  62  3.3  Sampling/Reading  70  4.1  Comparison  Strategy  b e t w e e n TDR a n d g r a v i m e t r i c d a t a f o r s a n d y  Loam s o i l 4.2  Comparison  77 b e t w e e n TDR a n d g r a v i m e t r i c d a t a f o r s i l t  loam s o i l 4.3  79  Sandy loam s o i l  temperatures a t d i f f e r e n t  b e f o r e and a f t e r 4.4  Silt  loam s o i l  Sandy loam s o i l  4.6  4.7  Silt  loam s o i l  82 depths  surface i r r i g a t i o n  84  temperatures a t d i f f e r e n t  b e f o r e and a f t e r  depths  surface i r r i g a t i o n  temperatures a t d i f f e r e n t  b e f o r e and a f t e r 4.5  58  depths  trickle irrigation  87  temperatures a t d i f f e r e n t  depths  b e f o r e and a f t e r  trickle irrigation  Percent of t o t a l  a p p l i e d water s t o r e d i n d i f f e r e n t  d e p t h s o f sandy loam s o i l under s u r f a c e i r r i g a t i o n  at different system  89  temperatures 96  4.8  P e r c e n t of t o t a l a p p l i e d water s t o r e d i n d i f f e r e n t depths of s i l t loam s o i l a t d i f f e r e n t  temperatures  under s u r f a c e i r r i g a t i o n system 4.9  99  P e r c e n t of t o t a l a p p l i e d water s t o r e d i n d i f f e r e n t depths of sandy loam s o i l a t d i f f e r e n t temperatures under t r i c k l e i r r i g a t i o n system  4.10  103  P e r c e n t of t o t a l a p p l i e d water s t o r e d i n d i f f e r e n t depths of s i l t loam s o i l a t d i f f e r e n t  temperatures  under t r i c k l e i r r i g a t i o n system 4.11 V o l u m e t r i c m o i s t u r e c o n t e n t p r o f i l e s of sandy  106 loam  s o i l a t d i f f e r e n t depths and temperatures under surface i r r i g a t i o n 4.12  V o l u m e t r i c m o i s t u r e c o n t e n t p r o f i l e s of s i l t  114 loam  s o i l a t d i f f e r e n t depths and temperatures under surface i r r i g a t i o n 4.13 V o l u m e t r i c m o i s t u r e c o n t e n t p r o f i l e s of sandy  116 loam  s o i l a t d i f f e r e n t depths and temperatures under trickle irrigation 4.14 V o l u m e t r i c m o i s t u r e c o n t e n t p r o f i l e s of s i l t  119 loam  s o i l a t d i f f e r e n t depths and temperatures under trickle irrigation  120  4.15 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer D  x  (%) d i s t r i b u t i o n i n s a n d y  (0-15cm) u n d e r s u r f a c e  i r r i g a t i o n system  124  4.16 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer D  2  (%) d i s t r i b u t i o n i n s a n d y  (15-3Ocm) u n d e r s u r f a c e  i r r i g a t i o n system  126  4.17 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer D  3  (%) d i s t r i b u t i o n  i n sandy  (3 0-45cm) u n d e r s u r f a c e  i r r i g a t i o n system  128  4.18 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer D  4  (%) d i s t r i b u t i o n  i n sandy  (45-60cm) u n d e r s u r f a c e  i r r i g a t i o n system 4.19 W e t t i n g  129  front locations at different  loam s o i l  under s u r f a c e i r r i g a t i o n system  4.2 0 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  depths f o r sandy 13 0  (%) d i s t r i b u t i o n i n s i l t  i n l a y e r D]. (0-15cm) u n d e r s u r f a c e  i r r i g a t i o n system  132'  4.21 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer D  2  (%) d i s t r i b u t i o n i n s i l t  (15-30cm) u n d e r s u r f a c e  i r r i g a t i o n system  133  4.22 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer D  i r r i g a t i o n system  3  (%) d i s t r i b u t i o n  in silt  (3 0-45cm) u n d e r s u r f a c e 13 5  4.23 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer  D  4  (%) d i s t r i b u t i o n i n s i l t  (45-60cm) u n d e r s u r f a c e  i r r i g a t i o n system 4.24 W e t t i n g  front  loam s o i l  13 6  locations  at different  under s u r f a c e i r r i g a t i o n system  4.25 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  depths f o r s i l t  i n layer  (%) d i s t r i b u t i o n i n s a n d y  Di (0-15cm) u n d e r  trickle  i r r i g a t i o n system  140  4.2 6 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer  D  2  (%) d i s t r i b u t i o n i n s a n d y  (15-30cm) u n d e r  trickle  i r r i g a t i o n system  142  4.27 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer  D  3  (%) d i s t r i b u t i o n i n s a n d y  (3 0-45cm) u n d e r  trickle  i r r i g a t i o n system  143  4.2 8 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer  D  4  (%) d i s t r i b u t i o n i n s a n d y  (45-60cm) u n d e r  trickle  i r r i g a t i o n system 4.29 W e t t i n g f r o n t loam s o i l  144  locations  at different  depths f o r sandy  under t r i c k l e i r r i g a t i o n system  4.3 0 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer  i r r i g a t i o n system  137  146  (%) d i s t r i b u t i o n i n s i l t  Di (0-15cm) u n d e r  trickle 148  4.31 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer  D  2  (%) d i s t r i b u t i o n i n s i l t  (15-3Ocm) u n d e r s u r f a c e  i r r i g a t i o n system  149  4.32 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer  D  3  (%) d i s t r i b u t i o n  (30-45cm) u n d e r  in silt  trickle  i r r i g a t i o n system  151  4.33 V o l u m e t r i c m o i s t u r e c o n t e n t loam s o i l  i n layer  D  4  (%) d i s t r i b u t i o n i n s i l t  (45-60cm) u n d e r  trickle  i r r i g a t i o n system 4.34 W e t t i n g  front  loam s o i l  locations  152 at different  depths f o r sandy  under s u r f a c e i r r i g a t i o n system  154  ACKNOWLEDGEMENTS I w i s h t o e x p r e s s my most s i n c e r e g r a t i t u d e t o my a c a d e m i c advisor,  D r . S i e t a n C h i e n g , a man o f i n t e l l i g e n c e and  patience  whose e x p e r t  and  assistance,  and continuous  have g r e a t l y c o n t r i b u t e d  research  enlightenment.  graduate  work  w i t h a few My Lo,  H i s kindness  and manuscript  D e n i s R u s s e l l and  t o my e d u c a t i o n a l a n d and guidance  preparation  cannot  be  during  my  described  t o my c o m m i t t e e members Dr.  Dr.  Hans S c h r e i e r ,  review, constructive c r i t i c i s m , I  encouragement,  words.  heartfelt gratitude  Dr.  guidance,  unlimited  would  specially like  for their  Victor  guidance,  and suggestions.  t o thank N e i l Jackson  and Jurgen  Pehlke. Acknowledgments Muhammad A k b a r Khan,  a r e extended Zahid  for  their  words  H. W a n i , D r .  Mahmood, D r . D o s t Mohammad  A b h i n a n d a n J a i n , Sumant J h a , Mueed  t o Dr. A l t a f  Muhammad Nadeem U s m a n i ,  o f wisdom,  support,  Baloch, and Irem  encouragement a n d  friendship. My  warm and  deep a p p r e c i a t i o n t o my b r o t h e r s ,  all  other  f a m i l y members f o r t h e i r p r a y e r s ,  and  moral  support.  S p e c i a l t h a n k s t o Dr.  love,  s i s t e r s , and encouragement,  A b d u l Hameed B a j o i , C h i e f  Scientific  Officer,  Agricultural  Balochistan, financial  Pakistan  Research  Institute,  Sariab,  Quetta,  f o r g r a n t i n g me a Ph.D., s c h o l a r s h i p and  support, I r e a l l y a p p r e c i a t e i t .  Appreciation  i s extended to Ms. J u l i a  members of the B i o l o g i c a l  Engineering  Sung and a l l s t a f f  Program a t The U n i v e r s i t y  of B r i t i s h Columbia, Vancouver, Canada.  DEDICATION Dedicated to my great parents Dr. Muhammad Hassan Khan and Mrs. Hassan Khan,  for their  always  that, I c o u l d accomplish  telling  mind t o .  me  love, continuous  support  anything  I l o v e you both and may you l i v e long.  and f o r I s e t my  CHAPTER I INTRODUCTION Maintaining  adequate  soil  moisture  c r u c i a l i n a c h i e v i n g good p l a n t growth. soil  moisture  i s essential  to keep  i n the  root  zone  is  Accurate measurement of the  right  level  of  soil  moisture. Water moves downwards v e r t i c a l l y and sideways from the source f o r bare s o i l s and  sideways  movement of water  (Hillel, forms  1982).  zone i s of p r a c t i c a l  least  be  zone where the  1983).  The wetted  importance as i t r e p r e s e n t s the amount of  s o i l water s t o r e d i n the root zone. at  T h i s downwards  a wetted  main root-zone of the p l a n t develops (Banami,  horizontally  I t s depth and width s h o u l d  equal to i f not s l i g h t l y b i g g e r than the  depth and width of the p l a n t root system.  rooting  Therefore, the volume  and the p a t t e r n of the wetted s o i l becomes an o b j e c t i v e  rather  than an end r e s u l t of the design process of an i r r i g a t i o n system (Zur,  1996).  The  size  and  shape  of the wetted  area  largely  depends on the type of s o i l and the water a p p l i c a t i o n r a t e . wetted area i s l a r g e s t f o r low intake a b i l i t y s o i l s and  smallest  for  high  intake  rate  soils  The  (clay s o i l s )  (sandy  soils) .  S i m i l a r l y , the shape of the wetted area f o r low intake s o i l s has more spread h o r i z o n t a l l y than v e r t i c a l l y and v i c e v e r s a f o r h i g h  intake such  soils.  as  I t a l s o depends  total  ( J u r y and  irrigation  1977;  may  R i s s e and Chesness,  show  a  pronounced  the occurrence  growing  season.  of moisture  content  moisture  s u c t i o n a t a low l e v e l .  to  wet  leaching this,  the  out  the  i n the  soil  zone  at  in  yield  frequency  to  time d u r i n g  the  a  high  level  and  avoid  water.  impeding In order  patterns  plant  root  zone  percolation  along  losses  1.1  Surface  direct  water  taken  to  under  achieve  different  minimize  w h i l e r e p l e n i s h i n g s o i l water i n the  the  depend  entire  length  directly  on  of  field.  irrigation  Deep system  evenly water i n f i l t r a t e s  ( G o l d h a m e r , 1987) .  Irrigation  Surface i r r i g a t i o n applying  soil  evaluated.  p e r f o r m a n c e w h i c h depends m a i n l y on how across the f i e l d  soil  aeration,  A p r i m a r y g o a l o f good i r r i g a t i o n management i s t o deep p e r c o l a t i o n o f water,  when  However, c a r e s h o u l d be  distribution  s y s t e m s must be  1989).  q u a n t i t y and  e x c e s s i v e l y to  water  frequency  a c h i e v e d by m a i n t a i n i n g  n u t r i e n t s or wasting  soil  irrigation  root  criteria  irrigation  s t r e s s a t any  T h i s c a n o n l y be  moisture  design  increase  i s provided i n sufficient  prevent  not  irrigation  volume of w a t e r a p p l i e d and  Earl,  Crops  on  to  i s t h e o l d e s t and most common m e t h o d o f  croplands.  d i v e r s i o n s from  rivers  The and  water streams,  sources pumped  may  include  flows  from  groundwater  basins  (Walker  1987).  The  most  and  common  irrigation,  border  flooding.  In  costs,  most  methods on  the  unskilled In  surface  of  the  surface  furrow  irrigation  conventional (deep  i s the  the b a s i s  of  l o w e r c a p i t a l and  maintenance,  and  the  surface  irrigation,  surface  losses,  non  percolation)  a p p l i c a t i o n of  over  and  (surge,  w a t e r as  conventional  uniformity  of  continuous  irrigation  water  a  is  time across  eliminated  by  Intermittent  air  continuous  distribution  opportunity  surface  surface sub-  operating  ability  to  use  (runoff)  and  uniformity  of  To  overcome o r  pulse)  irrigation,  series  of  shown much i m p r o v e m e n t s i n d i s t r i b u t i o n u n i f o r m i t y  because of  wild  o v e r s p r i n k l e , t r i c k l e , and  minimize these problems, i n t e r m i t t e n t  losses  basin  and  countries,  w a t e r d i s t r i b u t i o n have been the major problems.  in  are  labor.  subsurface  which  impoundments  methods  developing  favored  s i m p l i c i t y of  from  irrigation  irrigation,  i r r i g a t i o n methods a r e irrigation  diversions  due the  increasing  to  the  layer  entrapment  s e a l i n g due  consolidation, i n the  soil.  and  case  of  The  of  the  rate  in  advance of  non-  conventional infiltration  These d i f f e r e n c e s  rate  has  reduction  application.  differences  field.  a p p l i c a t i o n increases  surface  in  surges,  can  be  stream.  advance  stream  to s o i l p a r t i c l e rearrangement, more d i f f u s e d w e t t i n g The  intermittent  c o m p a r e d t o c o n t i n u o u s a p p l i c a t i o n has  front,  irrigation,  and as  b e e n p r o m o t e d as a method  to  i n c r e a s e t h e u n i f o r m i t y of water and c h e m i c a l s d i s t r i b u t i o n ,  a n d r e d u c i n g r u n o f f a n d deep p e r c o l a t i o n  1.2  losses.  Trickle/Drip Irrigation  Trickle  irrigation  beneath the s o i l  i s t h e s l o w a p p l i c a t i o n o f w a t e r on  s u r f a c e by d r i p , s u b s u r f a c e , b u b b l e r , and s p r a y  systems.  W a t e r i s a p p l i e d as d i s c r e t e o r c o n t i n u o u s d r o p s ,  streams,  or  miniature spray  through  p l a c e d along a water d e l i v e r y l i n e . a  pipe  distribution  network  emitters  or  low  pressure.  and g r a v i t y  by  from  outlet Water  capillarity  (US S o i l C o n s e r v a t i o n S e r v i c e ) .  Trickle eliminate  The  i s c a l l e d an e m i t t e r .  from the e m i s s i o n p o i n t s through the s o i l  tiny  applicators  Water i s d i s t r i b u t e d  under  d e v i c e t h a t emits water to the s o i l flows  or  irrigation  the need  systems  for land  reduce the l a b o r requirements,  leveling,  and  increase  irrigation  efficiency. Properly  designed  and  managed  commonly a c h i e v e a b e t t e r u n i f o r m i t y irrigation zone,  maintains higher s o i l  which  increases  micro-irrigation (Goldhamer,  water p o t e n t i a l s  the a v a i l a b i l i t y  t h u s e n h a n c i n g p l a n t g r o w t h and  1987).  of water  systems Trickle  i n the to the  root plant  yield.  A v e r y i m p o r t a n t f a c t o r t o be c o n s i d e r e d w h i l e d e s i g n i n g a t r i c k l e i r r i g a t i o n system i s the s o i l water d i s t r i b u t i o n the  emitters  (Martin et a l . ,  1984),  as  beneath  the geometry of w e t t e d  soil  under a p o i n t  source i s r e p r e s e n t a t i v e  s i t u a t i o n i n t r i c k l e i r r i g a t i o n design important c o n s i d e r a t i o n i n the design the  volume of  known  in  soil  order  r e q u i r e d to wet  wetted by  to  source  is  The  primarily  Chesness, The  the  total  a  volume of function  emitters  wetted  from a  soil  texture,  the  point the  (Risse  1989).  considered  to  be  enough water and  restricted  volume.  vulnerable  to  continuously,  I t i s a proven  grown on l e s s than 10% the  normal  nutrients  root  are  zone  of what i s  of  supplied  fact  a  field,  within  this  However, crops become extremely s e n s i t i v e even a  system or schedule.  slight  I f the  d i s r u p t i o n of  system does not  crop f a i l u r e can r e s u l t as  i s extremely s m a l l . moisture  be  f a c t that d r i p i r r i g a t i o n wets only a small p o r t i o n of  generally  and  of  must  the t o t a l volume of water a p p l i e d  t h a t even l a r g e t r e e s can be  and  This  to ensure that p l a n t  the s o i l volume can a l s o become a problem.  provided  Another  irrigation is  number  soil  of  practical  1996).  of t r i c k l e  l a r g e enough volume of s o i l  a p p l i c a t i o n r a t e , and and  (B. Zur,  a s i n g l e emitter.  determine  water needs are met.  of most  In a d d i t i o n , accurate  distribution  pattern  t a i l o r i n g the e m i t t e r spacing  irrigation  operate p e r f e c t l y the s o i l  moisture  knowledge of the  knowledge  (Hillel,  the  1980).  is  required  soil for  1.3  Temperature E f f e c t on S o i l Water Movement  Under subject  natural  to  gradients  conditions,  continuous  produced  by  the  root  temperature these  zone  changes.  temperature  the  liquid  classified  as  phases. diurnal  Temperature (daily)  and  soils  The  changes  m o i s t u r e t o f l o w f r o m warmer t o c o o l e r a r e a s and  of  thermal  cause  soil  i n both the  vapor  changes  annual.  i n the Daily  soil  changes  beneath  i n the  soil  may  be  significant  t h e r o o t zone o f most c r o p s  There  are  two  thermal/temperature s u r f a c e w h i c h may  types  of  to  depths  in  the  moisture  soil  flow  near  change d i r e c t i o n e v e r y 12 h o u r s  c h a n g e s d i r e c t i o n e v e r y 6 months  the  c o n s i d e r e d whenever m o i s t u r e , s a l t , the  water  soil's  surface layers.  a n d n u t r i e n t s may  be  or heat  The  by soil  (diurnal),  and  profile  (annual/seasonal) .  S t u d i e s h a v e shown t h a t t h e r m a l w a t e r  in  far  induced  t h e l o n g t e r m t h e r m a l m o i s t u r e f l o w deep w i t h i n t h e s o i l which  while  ( C a r y , 1966) .  flows  gradients:  are  temperature  c h a n g e s a r e commonly s i g n i f i c a n t t o a d e p t h o f 2 0 t o 3 0cm, annual  are  net  transport should  be  fluxes are s t u d i e d  transfer  of  the  soil  s i g n i f i c a n t l y a f f e c t e d by t h e r m a l l y  i n d u c e d m o i s t u r e f l o w by c h a n g i n g t h e m o i s t u r e c o n t e n t g r a d i e n t s and  the  capillary  importance under  head  caused  by  conductivity.  It  indicates  the  relative  o f t h e r m a l m o i s t u r e f l o w as compared t o m o i s t u r e gradients. gas  phase  The  mass  expansion  flow  of  vapors  and  contraction  flow  in soils  is  under  the  i n f l u e n c e of the d i u r n a l  t h e r m a l wave p a s s i n g t h r o u g h t h e  root  zone. The  possible  reasons  f o r water  flow i n s o i l s  in  phase under the i n f l u e n c e of temperature g r a d i e n t s can i)  surface tension  of  water  warmer  to  surface tension ii)  soil  moisture  cooler  areas  under  the  of  a  gradient. suction  moisture transfer  also  i n c r e a s e s as  the  temperature  results  from a net motion  flow. generated  random k i n e t i c e n e r g y c h a n g e s a s s o c i a t e d w i t h t h e bond  the  could flow  influence  drops, which could c o n t r i b u t e to the moisture iii)  be:  a g a i n s t a i r i n c r e a s e s as  temperature drops, moisture i n unsaturated s o i l from  liquid  distribution  which  develops  under  by  hydrogen  temperature  gradient. iv)  another  possibility  could  be  the  flow  thermally induced osmotic gradients. will  resulting  from  Most d i s s o l v e d  salts  spontaneously d i f f u s e through a s o l u t i o n  f r o m warmer  areas i n t o cooler areas. V a r i o u s s t u d i e s have i n d i c a t e d t h a t a s i g n i f i c a n t w a t e r may at  f l o w of  o c c u r t h r o u g h s m a l l p o r e s f r o m warm t o c o o l a r e a s e v e n  saturation.  gradients,  this  Compared  to  the  flux  f l o w becomes r e l a t i v e l y  arising  from  head  more i m p o r t a n t as  the  h y d r a u l i c c o n d u c t i v i t y decreases. The  relative  importance  of  thermally  induced  flow  rises  r a p i d l y i n u n s a t u r a t e d s o i l s as t h e m o i s t u r e c o n t e n t d e c r e a s e s .  The in  decrease  i n moisture  the thermal  flow.  liquid  content  i s accompanied by a  decrease  f l o w and by an i n c r e a s e i n vapor  moisture  A t any g i v e n moisture  moisture  flux  increases  content  faster  with  the thermal rising  vapor  mean  phase  temperatures  than t h e l i q u i d phase f l u x because o f t h e e x p o n e n t i a l dependence o f v a p o r p r e s s u r e on  temperature.  S e v e r a l models t o determine have been developed. require  are  based  on  approximated  trickle  data,  which l i m i t s  Some d e s i g n p r o c e s s e s tables  wetted  application  (empirical  radii  usefulness i n  ( K a r m e l i & K e l l e r , 1975)  calculations)  which  These  estimates  often  supply  lead to  systems b e i n g e i t h e r under o r over  (Risse and Chesness, Therefore  their  f o r g e n e r a l i z e d t e x t u r e s and v a r i o u s  r a t e s and volumes.  irrigation  source  But these models a r e o f t e n c o m p l i c a t e d and  extensive s o i l  design process.  t h e f l o w from a p o i n t  designed  1989).  t h e r e i s a need f o r f u r t h e r improvements o f t h e  e x i s t i n g guidelines f o r determining  the wetted  soil  volume  from  an i r r i g a t i o n s y s t e m . S i n c e s o i l w a t e r d i s t r i b u t i o n p a t t e r n s f o r d i f f e r e n t s o i l s a n d d i s c h a r g e r a t e s c a n be t a k e n as a g u i d e f o r e f f i c i e n t d e s i g n , o p e r a t i o n , a n d management o f i r r i g a t i o n  system  (Angelakis e t a l . ,  1993), t h i s study i s i n t e n d e d t o improve t h e  understanding  the  temperatures irrigation  of on  wetted  operations.  effects  of  patterns  soil under  type  and  surface  different  and  trickle  1.4  S o i l M o i s t u r e Measurement by Time Domain R e f l e c t o m e t r y  1.4.1  Histoiy As  early  1939,  as  g e o l o g i s t s and  others  recognized  r e l a t i o n s h i p between the d i e l e c t r i c p r o p e r t i e s of s o i l , other  materials,  and  their  moisture  content.  a  rock and  However,  they  l a c k e d the i n s t r u m e n t a t i o n necessary to make f u l l use of i t . Time Domain Reflectometry, commonly known as TDR, developed as the r e s u l t of World War  II radar r e s e a r c h , o f f e r e d  a method to d e f i n e these  dielectric  advent  research oscilloscopes  of  1960's, TDR  commercial  TDR  relationships.  i t became f e a s i b l e to t e s t t h i s new  technology  is  the  "cutting  largely  edge"  With  i n the  1.4.2  early  technology. Today,  methodology  for  d i v e r s e a p p l i c a t i o n s i n c l u d i n g the d e t e r m i n a t i o n of b a s i c water, m a t e r i a l / w a t e r  the  many soil  relationships.  P r i n c i p l e s of O p e r a t i o n  The  d i e l e c t r i c p r o p e r t i e s of s o i l  s o l i d s and water are of  considerable p r a c t i c a l interest. D i e l e c t r i c material i s defined as a m a t e r i a l that i d e a l l y conducts no e l e c t r i c i t y , g l a s s , wood, p l a s t i c , The  dielectric  dielectric The  i t a l s o i n c l u d e s dry a i r and pure water.  constant  i s the r a t i o  ( i n s u l a t o r ) to that of f r e e  practical  f o r example,  interest  stems from  of the c a p a c i t a n c e w i t h space. the f a c t  t h a t dry  soil  has a d i e l e c t r i c constant range of 2 to 4 compared to v a l u e s of  78 to 8 1 f o r water. Therefore, the d i e l e c t r i c p r o p e r t i e s provide an  e x c e l l e n t measure of the water content  Mansukhani, 1 9 7 6 ) .  Topp et a l . ( 1 9 8 0 )  of s o i l  ( S e l i g and  p l a c e d d i f f e r e n t type of  s o i l s and s o i l l i k e m a t e r i a l s around c o a x i a l t r a n s m i s s i o n with  5 cm spacing and 1 0 0 or 3 0 cm l e n g t h and found  dielectric  constant  measurements  t h a t the  was o n l y a f f e c t e d by water content.  were  independent  of  soil  type,  lines  soil  These  density,  temperature and s o l u b l e s a l t s . TDR u t i l i z e s the p r i n c i p l e of converting the t r a v e l time of a high  frequency,  content.  electromagnetic  In p r a c t i c e , TDR generates  pulse  into volumetric  water  a f a s t - r i s e p u l s e and sends  i t a t the speed of l i g h t down a t r a n s m i s s i o n l i n e c o n s i s t i n g of two p a r a l l e l Waveguides (probes) the  soil.  The v e l o c i t y  that are i n s e r t e d o r b u r i e d i n  of propagation  of the h i g h  frequency  wave i n s o i l i s determined p r i m a r i l y by the water content.  The  wave i s r e f l e c t e d from the open ends of the probes and r e t u r n s along the o r i g i n a l path.  By microprocessor,  the t r a v e l time of  the wave i s used to d i r e c t l y c a l c u l a t e the d i e l e c t r i c of  the s o i l .  The a c t u a l time delay  v o l u m e t r i c water content(%) TDR  gives  research  (nano-second) and c o r r e l a t e d  a r e d i g i t a l l y d i s p l a y e d on screen.  scientists,  c o n s u l t a n t s the power and f l e x i b i l i t y  commercial  growers,  and  to measure and l o g water  r e l a t i o n s h i p s of s o i l s and other m a t e r i a l s by a f a s t , easy to use method.  constant  accurate,  I t e l i m i n a t e s the need f o r u s i n g  nuclear  based i n s t r u m e n t a t i o n and the a s s o c i a t e d r a d i a t i o n , h e a l t h and  s a f e t y hazards.  TDR  the  for  requirement  eliminates s i t e s p e c i f i c costly,  specialized  calibration  licensed  and  personnel  a s s o c i a t e d w i t h neutron probes, and a l s o p r o v i d e s a u t o - l o g g i n g capabilities fully  field  several  days  not  practical  portable,  and  or weeks,  w i t h n u c l e a r techniques. can be  can be  left  at a  accessed from  remote a  TDR site  is for  laboratory  or  office. The  sensitivity  of TDR  i n pure water  decreases when the  d i s t a n c e from the plane of the wire i n c r e a s e s .  There are  two  regions of s e n s i t i v i t y . The h i g h s e n s i t i v i t y r e g i o n extends only to  8.5  mm  from the plane of the probe and the low  r e g i o n extends to 46 mm  from the plane of the probe.  r e g i o n of s e n s i t i v i t y i s 22 mm  1.5  sensitivity An average  from the plane of the probe.  J u s t i f i c a t i o n o f Study  The  wetted  zone as  a result  major p l a n t root system develops. geometry and d i s t r i b u t i o n  of i r r i g a t i o n  i s where  the  A b e t t e r understanding of the  p a t t e r n s of water i n s o i l  i s of v i t a l  importance i n the optimum design, o p e r a t i o n , and management of any i r r i g a t i o n Many  system.  studies  g r e a t e r or l e s s e r soil.  Some  gravitational  have  shown  that  temperature  affects  to  a  degree, p r a c t i c a l l y every p h y s i c a l process i n of  the  most  important  processes  include  flow of water, c a p i l l a r y movement and r e t e n t i o n of  m o i s t u r e , a n d d i f f u s i o n and f l o w o f g a s e s e t c . t e m p e r a t u r e upon t h e s e f a c t o r s i n s o i l viscosity,  The  i n f l u e n c e of  i s known f r o m t h e l a w s o f  s u r f a c e tension, s o i l water m a t r i c p o t e n t i a l ,  diffuse  d o u b l e - l a y e r t h i c k n e s s , r e l a t i v e p e r m e a b i l i t y , and e x p a n s i o n o f g a s e s a n d l i q u i d s as a f f e c t e d b y t e m p e r a t u r e . It  i s the purpose of t h i s  temperature irrigation  on  water  s t u d y t o examine the e f f e c t s  distribution  systems.  two  soils  water d i s t r i b u t i o n p a t t e r n s i n s o i l under m i c r o - i r r i g a t i o n ,  but  a t t e n t i o n has been g i v e n towards  distribution  i r r i g a t i o n systems  patterns  in soil  under  conducted  two the  water  have been  under on  very l i t t l e  Many s t u d i e s  in  of  the comparison surface  and  micro-  i n s o i l s at d i f f e r e n t temperatures.  More r e s e a r c h i s needed t o c l a r i f y s o i l w a t e r p h y s i c a l c h e m i c a l e f f e c t s on r o o t g r o w t h .  An e n h a n c e d  this  using  phenomenon  will  help  in  f e r t i g a t i o n to produce d e s i r e d root This  study w i l l  factors like s o i l  improve  unique  in  micro-irrigation  two  that,  system.  t h e u n d e r s t a n d i n g o f some o f  i t investigates  i r r i g a t i o n methods  d i f f e r e n t temperatures of and  t h i s study w i l l  and  the  t y p e , t e m p e r a t u r e and i r r i g a t i o n method, w h i c h  p a t t e r n s i n two d i f f e r e n t s o i l under  and  understanding of  can a f f e c t the water d i s t r i b u t i o n p a t t e r n s i n s o i l . is  of  types  the  water  This study distribution  (sandy loam and s i l t  loam)  ( s u r f a c e and m i c r o - i r r i g a t i o n ) the  results  r e f i n e the d e s i g n i n g and managing o f  surface  micro-irrigation  (up t o 40°C) .  systems  Additionally,  at  for different  soil  types  under  different  climatic  conditions.  To t h e a u t h o r ' s k n o w l e d g e t h e r e i s no p u b l i s h e d s t u d y has  considered  the  effect  d i s t r i b u t i o n p a t t e r n s under  of  temperature  different  on  soil  that water  i r r i g a t i o n methods.  The  temperature ranges i n v e s t i g a t e d i n t h i s study r e p r e s e n t those of arid  and  semi-arid  regions,  such  as  Balochistan  of  Pakistan,  where i r r i g a t i o n i s p r a c t i c e d under an a i r t e m p e r a t u r e range 30 t o 40  1.6  °C.  Objectives  The the  of  main o b j e c t i v e  effects  of d i f f e r e n t  of t h i s  research study i s to evaluate  t e m p e r a t u r e s on t h e w a t e r  p a t t e r n s i n two d i f f e r e n t s o i l s (sandy loam and s i l t two  i r r i g a t i o n systems  objective  was  (surface  a c h i e v e d by  and  water  d i s t r i b u t i o n p a t t e r n s i n sandy  under  s u r f a c e and t r i c k l e i r r i g a t i o n systems °C.  loam)  under  micro-irrigation).  conducting studies  t e m p e r a t u r e s o f 30, 35, a n d 40  distribution  loam  and  The  to  examine  silt  loam  at three  the  soils  different  CHAPTER I I LITERATURE REVIEW Research  r e l a t e d t o water  have been conducted w o r l d wide  Mostaghimi  provided  1983).  These  u n d e r s t a n d i n g of. t h e e f f e c t s  systems on water d i s t r i b u t i o n p a t t e r n s i n s o i l . method  directly  patterns  or  i n soil,  indirectly  surface  losses and s a l i n i t y .  i n soil  e t a l . 1 9 9 3 ; P e l l e t i e r and Tan,  and M i t c h e l l ,  a good  patterns  ( R o b i n s o n , 1 9 9 9 ; Abu-Awwad, 1 9 9 9 ;  Shao a n d H o r t o n , 1 9 9 8 ; A n g e l a k i s 1993;  distribution  affects  runoff,  water  studies  have  of i r r i g a t i o n The i r r i g a t i o n distribution  deep p e r c o l a t i o n , n u t r i e n t  T h e c h a n g e f r o m one i r r i g a t i o n s y s t e m t o  a n o t h e r may change s o i l w a t e r d i s t r i b u t i o n p a t t e r n s i n t h e p l a n t root  zone.  2.1  F i e l d Plot  Studies  Horizontal  w a t e r movement i n two s o i l s  (Kfar Hayarok and  H a t z e r i m s o i l s ) was s t u d i e d b y G o l d b e r g e t a l . ( 1 9 7 6 ) different  flow rates  and  volumes  five  surface  five  ( 1 . 0 , 2 . 0 , 4 . 2 , 9 . 2 , 1 8 . 4 l i t e r s p e r hour)  of water  (12,  24,  48,  p o i n t source w i t h the greatest discharge caused  using  runoff  f o r both  soils,  96,  192 l i t e r s ) . The  ( 1 8 . 4 l i t e r s p e r hour) which  would  n o t be  suitable under  forpractical  the point  increased  from  application maximum  indicating  source  1.0  that  The p o n d e d d i a m e t e r o f t h e w a t e r  increased  t o 9.2  volume.  lateral  use.  3-fold  l p h f o r each  However,  these  as  soil  studies  water  movement  increased  lateral  movement  i s more  the type  flow with  showed less  a  rate equal  that than  function  the 10%,  of the  volume o f water a p p l i e d than o f t h e f l o w r a t e .  Topp a n d D a v i s to measure t h e s o i l  (1985) u s e d Time Domain R e f l e c t o m e t r y moisture  content.  (TDR)  They u s e d p a r a l l e l  wire  t r a n s m i s s i o n l i n e s v a r y i n g i n l e n g t h f r o m 0.125 t o 1 m i n s t a l l e d vertically season.  a t three  sites  i n a cornfield  during  the planting  Topp e t . a l . (1980) showed t h a t w a t e r c o n t e n t  main f a c t o r r e s p o n s i b l e f o r the d i e l e c t r i c constant m a t e r i a l and t h a t other density An  water  content  of the s o i l  f a c t o r s s u c h as t e m p e r a t u r e , s o i l  o f sample and s a l t  e m p i r i c a l equation  was t h e  content  relating  had i n s i g n i f i c a n t  effects.  the d i e l e c t r i c constant  was d e v e l o p e d n o t o n l y  for coaxial  and t h e  transmission  l i n e s but also f o rp a r a l l e l p a i r s of transmission l i n e s in  the s o i l .  water content TDR  also  gave  discontinuities lines  and  impedance  The p a r a l l e l  lines  provided  profile  were u s e d .  additional  of water  content  along  t h e l i n e and  when  a  line  with  A t one o f t h e t h r e e s i t e s h o r i z o n t a l  vertical  discontinuities  placed  a good measure o f  regardless of the d i s t r i b u t i o n a  type,  were  transmission  with  electrical  installed  for  comparison.  Comparisons of water contents  by TDR  s a m p l e s showed s i m i l a r v a l u e s  f o r both the parameters.  measurements correlated  at  and  the a  same  yielding  transmission  location in  c o r r e l a t i o n even  A n a l y s i s of v a r i a n c e were  w i t h those from g r a v i m e t r i c  the  field  existed  over  Repeated  were the  showed t h a t a l l t h e t r a n s m i s s i o n  equivalent  values  and  that  l i n e s g a v e t h e minimum s t a n d a r d  highly  seasons. line  the  types  horizontal  e r r o r o f t h e mean.  D a t a f r o m t r a n s m i s s i o n l i n e s w i t h impedance d i s c o n t i n u i t i e s gave water  content  profiles  analyses  of  the  TDR  without  impedance  from  data  not The  but  d i s t u r b the study  t h e TDR  u s i n g TDR technique  demonstrated  the  TDR  Both  horizontally  transmission provide  and  technique  and  measurements line  considerable  an  a  The  a c c u r a c y has  been  i n both  installed  contents. which  in  the  authors  also  recommended  the  the  cases  i n the  soil.  lines  The  have  gave  variety  been  s e l e c t i n g the  need  lines.  for  t r a n s m i s s i o n l i n e s f o r e v a l u a t i n g the water content But  can  method  the v a r i a b i l i t y  vertically  flexibility  for  battery-powered  accurate  s a m p l e s and  configurations  results  transmission  with  is  water  lines  t h e a d v a n t a g e t h a t i t does  i n the f i e l d .  of  the  gravimetric analysis  that  o f a c c u r a c y d e p e n d e d on  satisfactory  Equivalent  has  found comparable to g r a v i m e t r i c limit  but  w e r e more c o m p l e x t h a n f o r t h e  measuring s o i l water content  the  measurement  s i t e a f t e r i n s t a l l a t i o n of  has  instrument,  single  discontinuities.  measuring water contents be a c h i e v e d  a  of  evaluated option  of  information.  f o r more  research  before using lines with  discontinuities.  Goldhammer e t a l . (1987) vs.  c o n d u c t e d a f i e l d s t u d y on  continuous flow i r r i g a t i o n  w i t h grower  and F r e s n o c o u n t i e s i n C a l i f o r n i a .  surge  cooperators i n Kern  Randomized p l o t s were  1,200  f e e t l o n g w i t h s o i l t y p e s o f Wasco s a n d y loam a n d a Panoche c l a y loam,  and  methods.  usually The  replicated  four  times  f o r both  irrigation  r e s u l t s i n d i c a t e d that water t r a v e l e d r a p i d l y  over  the  s o i l w e t t e d by p r e v i o u s s u r g e s and s l o w e d d r a m a t i c a l l y  once  dry  s o i l was  that  encountered.  The  overall  c o n c l u s i o n s were  surge i r r i g a t i o n a c c e l e r a t e d water advance r a t e s f o r b o t h s o i l s , and  generally  improved  distribution  of  infiltrated  water  and  d e c r e a s e d deep p e r c o l a t i o n .  L a f o l i e e t a l . (1989) a n a l y z e d t h e w a t e r f l o w u n d e r irrigation  trickle  on s t r a t i f i e d a n d a n i s o t r o p i c s o i l s a n d c o m p a r e d t h e  d a t a f r o m a f i e l d e x p e r i m e n t u s i n g loamy c l a y s o i l f r o m 24 plots  irrigated  irrigation  at d i f f e r e n t  efficiency  instrumental  and  rates  and  reduced  i n the p o p u l a r i t y  frequencies.  water  of t r i c k l e  stress  But a q u a n t i t a t i v e u n d e r s t a n d i n g of the s o i l water during  trickle  irrigation  numerical  model  content d i s t r i b u t i o n s ,  for predicting  during t r i c k l e  soil  irrigation  been  irrigation. distributions  i s imperative for optimizing  p r o d u c t i o n and m i n i m i z i n g deep p e r c o l a t i o n l o s s e s . proposed  Increased have  or drip  field  crop  A previously profile on  water  stratified  and  anisotropic soils,  was u s e d . R e s u l t s  for a typical  set of  experiments i n v o l v i n g four hours of i r r i g a t i o n and twenty hours of  redistribution  treatise.  Many  d i s c r e p a n c i e s w e r e n o t e d when t h e o b s e r v e d w a t e r c o n t e n t s  were  simulated  with  attributed soil  have been p r e s e n t e d  t h e model  t o the inadequate  hydraulic  a  majority  Moreover  c r u s t on s o i l  of the heterogeneous behavior  inclusion improved  of s o i l  crusting  predictions  them  other  of fine  water  could  be  unsaturated  problems  like  c a n be e x p l a i n e d w i t h t h e  and s o i l  of s o i l  of  characterization of  conductivity.  formation of a t h i n s o i l help  and  i n this  textured s o i l .  anisotropy contents.  The  resulted i n  The  conclusion  drawn from t h i s p a p e r c a n be summarized as a need f o r a c c u r a t e description  of  soil  hydraulic  p r e d i c t i o n of s o i l water content  Grantz  e t a t . (1990)  for a  during t r i c k l e  evaluated  v o l u m e t r i c s o i l - w a t e r content Hawaii.  properties  TDR  irrigation.  f o r measurement  i n an e x t e n s i v e sugarcane f i e l d i n  vertically  at  various  distances  from  i r r i g a t i o n l i n e at s i x locations i n a well-watered  to  the  field.  drip This  p r o t o c o l showed t h e d i u r n a l d e p l e t i o n o f s o i l w a t e r due  évapotranspiration  distance  of  Matched p a i r s o f p r o b e s , 0 . 3 5 9 m and 0 . 7 2 5 m l o n g , were  installed  sampling  reliable  and  the decline  from t h e d r i p i r r i g a t i o n  w i t h i n the surface 0.3 6 m of s o i l . soil-water  content  using  line,  i n soil  water  both occurring  with  largely  Independent measurements o f  gravimetric  methods . c o n f i r m e d  the  a c c u r a c y o f t h e TDR d e t e r m i n a t i o n s and v a l i d a t e d a u n i v e r s a l c a l i b r a t i o n f o r F e - r i c h Hawaiian s o i l s . developed  to  install  probes,  throughout t h e 2-yr crop c y c l e . arrays  o f TDR probes  suited  t o automation  analysis,  than  were  which  A r a p i d t e c h n i q u e was remained  functional  The study concluded t h a t spaced  safer,  of data  more c o n v e n i e n t ,  acquisition,  c o n v e n t i o n a l methods  and more  r e d u c t i o n , and  of assessing v o l u m e t r i c  water c o n t e n t .  Herkelrath  e t a l . (1991) developed  a multiplexing  time  domain r e f l e c t o m e t r y (TDR) system  f o r real-time monitoring of  volumetric s o i l moisture content.  The system was t e s t e d a t a  remote f i e l d  s i t e i n t h e Hubbard Brook E x p e r i m e n t a l F o r e s t i n  New Hampshire.  The average v a l u e o f s o i l m o i s t u r e c o n t e n t i n  the t o p 500 mm o f s o i l was measured every 4 hours f o r 1 y e a r a t 12 l o c a t i o n s w i t h i n a 12m by 18m p l o t .  They found  system f u n c t i o n e d w e l l except when t h e a i r temperature  that the dropped  below -15 °C, which caused the data l o g g e r tape r e c o r d e r t o s t o p . C a l i b r a t i o n s r u n on u n d i s t u r b e d s o i l cores d i d n o t compare w e l l with  p u b l i s h e d curves  developed  f o r mineral  soils,  probably  because o f h i g h s o i l o r g a n i c matter c o n t e n t .  The s t a n d a r d e r r o r  of  indicated  estimate  calibrations,  of  soil  moisture  was 0.02 cm /cm . 3  3  content,  The s t a n d a r d  by t h e  d e v i a t i o n of  r e p e a t e d m o i s t u r e c o n t e n t measurements made i n t h e f i e l d was 0.003 cm /cm . 3  3  The e f f e c t o f c a b l e l e n g t h on t h e TDR s i g n a l was  investigated. the  signal,  I t was  found that long c a b l e s tend to a t t e n u a t e  ultimately  making  the  measurement  impractical.  However, cable length had l i t t l e e f f e c t on the c a l i b r a t i o n up to a l e n g t h of 27 m.  The c o e f f i c i e n t of v a r i a t i o n of the moisture  content measurements taken at any given time ranged from 0 . 1 2 0.21  d u r i n g the  analysis spatial  of  test  soil  period.  moisture  variability  of  As  flow  predicted in  by  a  to  stochastic  heterogeneous  soil,  the measurements decreased  as  the  average  s o i l moisture i n c r e a s e d .  Jacobsen  and  gravimetrically  and  measured  time domain r e f l e c t o m e t r y soil  from  the  plough  locations.  The s o i l  sandy  clay  loam.  water  saturation.  around 1 . 3 5 relationship  X 10  3  (1993)  Schjonning  determined water  apparent  (TDR)  layer  dielectric  for a total  and  the  constant  by  samples  of  of 189  subsoil  at  contents  five  Danish  types ranged from a coarse sandy s o i l  Water contents v a r i e d Samples were packed or 1 . 5 5  between  X 10  the  3  kg m~. 3  from a i r dry to near at dry b u l k  densities  A t h i r d - o r d e r polynomial  v o l u m e t r i c water  apparent d i e l e c t r i c constant was  to a  content  and  the  found s u i t a b l e f o r c a l i b r a t i o n .  The r e l a t i o n s h i p d i f f e r e d from e a r l i e r r e s u l t s ; the d e v i a t i o n s c o u l d be e x p l a i n e d p a r t l y by d i f f e r e n c e s i n t e x t u r e . of  l i n e a r terms  matter  content  Inclusion  f o r dry bulk d e n s i t y , c l a y content and o r g a n i c in  the  calibration  equation  each  yielded  an  improvement i n the c o r r e l a t i o n ; t h i s improvement, although small  compared  with  t h e u n c e r t a i n t i e s i n t h e measured  constant  and i n the g r a v i m e t r i c a l l y  was s t a t i s t i c a l l y  significant.  clay  matter  and o r g a n i c  statistically  determined  dielectric  water  content,  Even a f t e r i n c l u s i o n o f d e n s i t y ,  content  i n the c a l i b r a t i o n  equation,  s i g n i f i c a n t d i f f e r e n c e s between t h e t e n s o i l  remained; t h i s suggests  types  t h a t r a t h e r complex i n t e r a c t i o n s between  t h e s o i l components a f f e c t t h e e l e c t r i c p r o p e r t i e s o f t h e s o i l .  Jacobsen  5m  (1993)  Schjonning  measured  the  apparent  c o n s t a n t b y t i m e d o m a i n r e f l e c t o m e t r y (TDR) i n 3 . 5 m  dielectric X  and  field  plots  at three  locations during  a  soil  moisture  d r y i n g p e r i o d u s i n g probes i n s t a l l e d v e r t i c a l l y t o depths of 15, 30  a n d 60  cm.  comparison. sand  contents  were measured f o r  The t h r e e s o i l s i n v e s t i g a t e d w e r e a J y n d e v a d  (coarse  sandy  G r a v i m e t r i c water  loam  sandy mixed, (coarse  Hapludalf)  and  a  mesic  loamy  to  Ronhave  O r t h i c Haplohumod),  fine  loamy  sandy  loam  mixed, (loamy  coarse  an Askov  mesic  Typic  mixed,  mesic  c a l c a r e o u s T y p i c Agrudalf) having t o p s o i l c l a y contents o f 3, and  14%,  respectively.  d e v i a t i o n was h i g h e r by g r a v i m e t r y increased respect  volumetric 0.005-0.023.  f o r water contents  plots, determined  the  standard  b y TDR  than  ( 0 - 1 5 cm d e p t h ) . M o r e o v e r , t h e s t a n d a r d d e v i a t i o n  with to  For the f i e l d  11  the water  increasing TDR  clay  content,  measurements.  content  determined  They a l s o n o t e d  particularly  Standard  with  deviations f o r  b y TDR w e r e  i n the range  that the measuring depth  (0-15,  0-  30  and  0-60  cm)  d i d not affect  the v a r i a t i o n  of  the  TDR  m e a s u r e m e n t s i n a c o n s i s t e n t way.  P e l l e t i e r and Tan (1993) (TDR)  used t h e time domain r e f l e c t o m e t r y  t e c h n i q u e t o measure w a t e r i n t h e s o i l  wetting patterns peach  of drip  [Prunus p e r s i c a  distinct  and m i c r o j e t  irrigation  (L.) B a t s c h ] o r c h a r d .  system.  The 50% ASW  to derive  systems  in a  They n o t e d t h a t a  c o n e s h a p e o f >50% a v a i l a b l e s o i l w a t e r  f r o m t h e e m i t t e r down t o a d e p t h o f >45 drip  profile  (ASW) e x t e n d i n g  cm was o b s e r v e d i n t h e  zone i n t h e m i c r o j e t  s y s t e m was a n  e l o n g a t e d s e m i c i r c l e f r o m t h e s o i l ' s s u r f a c e down t o a d e p t h o f 35  cm.  The c o n c l u s i o n  o f t h e s t u d y was t h a t  TDR  c a n be  s u c c e s s f u l l y t o determine wetting patterns of various systems  to develop better i r r i g a t i o n  N i e l s e n e t a l . (1995) reflectometry the  layer.  scheduling.  t o measure w a t e r  Wave g u i d e s  water  h o u r l y by a data logger.  c o n t e n t s from  t h e TDR  were  computed  water c o n t e n t s o b t a i n e d from g r a v i m e t r i c s o i l v a l u e s were l i n e a r l y r e l a t e d of  ( r = 0.84) 2  installed  surface i n f i e l d  i n current c r o p - t i l l a g e history.  was i n t e r r o g a t e d  content i n  (probes) were  h o r i z o n t a l l y a t a d e p t h o f 25 mm b e l o w t h e s o i l plots differing  irrigation  s t u d i e d t o determine i f time-domain  (TDR) c o u l d b e u s e d  0 - t o 50-mm s o i l  used  Daily  The TDR  system  average  soil  and compared  with  sampling.  with gravimetric  The TDR samples  s o i l w a t e r c o n t e n t when wave g u i d e s were a t a d e p t h o f 25  mm,  b u t n o t when wave g u i d e s w e r e a t a d e p t h o f 13  Khan e t a l . ( 1 9 9 6 )  mm.  conducted f i e l d p l o t s t u d i e s t o evaluate  w a t e r a n d s o l u t e movement f r o m a p o i n t s o u r c e . the on  The p u r p o s e s o f  s t u d y were, t o i n v e s t i g a t e t h e e f f e c t s o f a p p l i c a t i o n r a t e s soil  water  and s o l u t e  regime,  to study  the e f f e c t of the  volume o f w a t e r a p p l i e d on t h e w e t t e d p a t t e r n s , of c o n c e n t r a t i o n study revealed  on t h e d i s t r i b u t i o n o f water and s o l u t e .  an  increase  i n rate  zone.  resulted  F o r t h e same a p p l i c a t i o n i n an i n c r e a s e  w e t t e d h o r i z o n t a l a r e a and a decrease i n t h e w e t t e d s o i l The  study also  input  found s o l u t e c o n c e n t r a t i o n  concentration,  Larger  applied  wetted and chemigated  volumes o f a p p l i e d  induce  volume, soil  increased  depth.  with  and a p p l i c a t i o n  v o l u m e was f o u n d  i n the  high  rate.  f o r higher  water.  I n many d r i p - i r r i g a t e d properties  The  a c l e a r r e l a t i o n s h i p between t h e a p p l i c a t i o n r a t e  and t h e shape o f t h e w e t t e d s o i l volume,  and t h e e f f e c t  fields,  variations  spatial variations i n soil  i n wetting  patterns  about  the  d r i p p e r s , r e s u l t i n g i n u n c e r t a i n t y i n the i n t e r p r e t a t i o n and use of  sensor-based  conducted  a study  analytical  tools  soil  water  information.  to v a l i d a t e the a n a l y t i c a l (models)  to quantify  hydraulic  properties  Or,  D.,  (1996)  r e s u l t s o f some  the e f f e c t s of  variation  i n soil  on w e t t i n g  Following  the c h a r a c t e r i z a t i o n of the s o i l hydraulic  spatial  patterns. properties  i n t h e s t u d y s i t e , w a t e r was s u p p l i e d f r o m a r r a y s o f s u r f a c e a n d subsurface  point  tensiometers installed  sources  a t constant  flow  rates.  a n d 100 t i m e domain r e f l e c t o m e t r y  at fixed positions relative  f l o w r a t e and source  About  160  (TDR) p r o b e s w e r e  t o the source  ( f o r each  l o c a t i o n ) and were m o n i t o r e d d a i l y .  The  r e s u l t i n g s p a t i a l moments o f m a t r i c h e a d a n d w a t e r c o n t e n t  were  compared w i t h a n a l y t i c a l model p r e d i c t i o n s . large discrepancy the  b e t w e e n measurements a n d p r e d i c t i o n s b a s e d o n  field-estimated variability  unsaturated  i n alpha  suggests that s o i l be b i a s e d  analytical  by the presence  model  was  capable  predict the v a r i a b i l i t y  i n a l p h a was u s e d .  of large pores.  should  This  of  using  Overall, the  information  on  i n flow attributes.  be v i e w e d  of v a r i a b i l i t y  the  i n soil hydraulic properties to However, e v e n w i t h  c h a r a c t e r i z a t i o n and s m a l l e r s o i l v a r i a b i l i t y ,  predictions extent  B e t t e r agreement  h y d r a u l i c p r o p e r t i e s measured under ponding  (permanent) s p a t i a l v a r i a b i l i t y  better soil  (the exponent o f t h e  hydraulic conductivity function).  was o b t a i n e d when a r e d u c e d v a r i a b i l i t y  may  Results revealed a  as f i r s t  approximations  i n m e t r i c head and water  model of the  content.  S a l a s e t a l . (1996) c o n d u c t e d a n e x p e r i m e n t t o d e t e r m i n e i f time-domain water content Probes  reflectometry  (TDR) c o u l d  be u s e d  t o measure t h e  a t d i f f e r e n t d e p t h s i n t h e 0 t o 75 cm s o i l  of three  wires  l e n g t h ) were i n s t a l l e d  (1/8 i n c h  diameter  and 3 0  cm  layer. exposed  i n f i e l d plots d i f f e r i n g i n current  crop-  fertilization history.  Measurements o f v o l u m e t r i c w a t e r  u s i n g b u l k d e n s i t y and g r a v i m e t r i c water calibrate  the  determined  b y TDR  with  is a  linear  that  there  TDR  method.  from  of  water  contents  g r a v i m e t r i c samples  relationship w i t h depth,  (small  offset  indicating  showed  but  same  slope)  of water  little  d i f f e r e n c e i n v o l u m e t r i c w a t e r c o n t e n t f r o m t h e 0 t o 75cm  depth.  content  c o n t e n t w e r e made t o  Comparison  those  content  that there i s  However, t h e TDR m e t h o d g i v e s c o n s i s t e n t l y  lower  water  c o n t e n t v a l u e s as compared w i t h v a l u e s o b t a i n e d by g r a v i m e t r i c determination. content  with  Continuous TDR  measurements  i n wet  and  dry  of p r o f i l e  periods  soil  during  water  the  i n d i c a t e d t h a t t h e mayor d i f f e r e n c e s i n v o l u m e t r i c w a t e r  year  content  c o r r e s p o n d t o t h e f i r s t 3 0 cm o f d e p t h .  2.2  Laboratory Studies  Gardner study  (1954) n o t e d t h e l a c k o f i n f o r m a t i o n r e g a r d i n g c o n s c i o u s of  the  effects  of  temperature  on  moisture  tension.  A c c o r d i n g t o h i s w o r k s , i t c a n be shown t h a t m o i s t u r e t e n s i o n i s not  independent  conducted  a  fluctuations gradients  of  study  temperature. of  the  i n tensionmeters  were p r i m a r i l y  water  i n tensionmeter  error  chargeable  to  due  cups the  Hiase  causes  of  and the  Kelley  (1950)  large  diurnal  r e a d i n g s and c o n c l u d e d  that the  t o temperature  and s o i l  and thus  instruments.  In  g r a d i e n t between attributable the  to  experimental  procedures  an attempt  system  interaction  actual  effect  studied.  t o reduce  of tensionmeter  of  The  was made  temperature  relationship  the effect  and t h e s o i l  on m o i s t u r e between  so t h a t t h e  tension  moisture  of the  could  tension  t e m p e r a t u r e was s t u d i e d i n t h r e e c a s e s w i t h c o a r s e s a n d , l o a m a n d muck s o i l The  a t constant moisture percentages  be and  sandy  condition.  r e l a t i o n s h i p s t e n d t o b e more i n c l i n e d t o w a r d s a c u r v i l i n e a r  than a s t r a i g h t - l i n e Thomas  (1921),  determining range.  function.  vapor  moisture  Therefore  Since the c l a s s i c a l  pressure tension  i t follows  has  been  widely  i n the r e l a t i v e l y that  studies of  as vapor  used  in  low moisture pressure  is a  f u n c t i o n o f temperature as w e l l as m o i s t u r e p e r c e n t a g e , m o i s t u r e tension  also  (1943)  a l s o d e r i v e d t h i s r e l a t i o n s h i p between m o i s t u r e  and  varies  temperature  with  from  capillary potential.  a  temperature.  consideration  E d e l f s e n and Anderson  of  free  tension  energy  Some o f t h e c o n c l u s i o n s d r a w n f r o m  and their  study are: •  Through i t s e f f e c t  on m o i s t u r e t e n s i o n ,  f a c t o r a f f e c t i n g t h e s o i l m o i s t u r e moving •  The s o i l  temperature  i s a  forces.  temperature and t h e temperature g r a d i e n t between  p l a n t s and t h e s o i l  on w h i c h t h e y a r e g r o w i n g a r e i m p o r t a n t  factors i n the a v a i l a b i l i t y of moisture to plants. T h u s , i n e s s e n c e i t c a n b e s a i d t h a t a s t u d y was c a r r i e d o u t t o d e t e r m i n e t h e e f f e c t o f t e m p e r a t u r e on s o i l m o i s t u r e t e n s i o n o f three  soils  a t constant moisture percentages  and the f i n d i n g s  support  a consistent  rate of 0.08 the that  tendency  f o r decrease  atmospheres p e r degree r i s e  r a n g e o f 0 t o 50 d e g r e e s  Celsius.  temperature-induced gradients  i n tension  at the  i n temperature  within  Regardless of the fact  exist  i n the s o i l  when t h e  t e n s i o m e t e r s a r e read, temperature has a r e l a t i o n s h i p w i t h t h e moisture tension i n the s o i l .  A l i z a h and H u l b e r t (1960) soil  s t u d i e d t h e r e l a t i o n s h i p between  t e x t u r e a n d w a t e r s u p p l y n e e d e d t h a t was more i m p o r t a n t i n  semi-arid  and  arid  climates  due  to  importance  of  water.  E x p e r i m e n t s w i t h ' t h r e e s o i l s were c o n d u c t e d i n g r e e n h o u s e s .  The  s o i l s u s e d w e r e a w a s h e d g r a v e l l y s a n d f r o m t h e edge o f K a n s a s River,  loam from t h e A - h o r i z o n o f an a l l u v i a l  soil  and a  silt  l o a m f r o m t h e A - h o r i z o n o f a l e v e l a l l u v i a l g r a s s l a n d s o i l . The experiments attempted to assess the d i f f e r e n c e s losses  i n soils  conditions.  of d i f f e r e n t  i nevaporation  t e x t u r e s under semi a r i d  climatic  Four d i f f e r e n t s e r i e s o f e x p e r i m e n t s were c o n d u c t e d  with varying  water  addition  levels  and r e s p e c t i v e f r e q u e n c i e s  a n d i t was c o n f i r m e d t h a t l e s s w a t e r e v a p o r a t e s f r o m c o a r s e t h a n from  the fine  inference  is  evaporation texture.  textured  soils  i n agreement  from  soil  i n semi-arid with  the  Evaporation  dry surfaces  This  knowledge of  of  different  are similar to evaporation  s u r f a c e s as l o n g as t h e s o i l through  earlier  a n d o b s e r v a t i o n s of- s o i l s  E v a p o r a t i o n r a t e s from s o i l  from water  conditions.  s u r f a c e remains wet.  i s controlled  primarily  by  factors  affecting  gradients. of  loams  the  The  and  vapor  diffusion,  s u r f a c e o f sands may  clays  due  to less  including  soil  temperature  d r y more r a p i d l y t h a n t h o s e  c a p i l l a r y movement o f w a t e r  s u r f a c e and t o l e s s w a t e r s t o r a g e .  The e f f e c t o f t e x t u r e  e v a p o r a t i o n v a r i e s w i t h t h e amount o f w a t e r a d d e d . light  rains  rainfall zone,  will  i s plenty  drought  because  the  soil  quickly  that  develops  the  from  soils  more - r a p i d l y  capacity  is  any  a r e wet in  more  of  the  than  in  important  root loams  than  the wet  The  was  added  in  water  textured  evaporation  being  evaporates and  from  support  help explain  (1964)  attributed  to  at  longer  fine  textured  the mesophytic  conducted  the  than  from  on  that  coarse  differences  vegetation  at  moisture  These e x p e r i m e n t s c o n f i r m  the hypothesis that  t h a n on f i n e t e x t u r e d s o i l s  Cary  quantities  i n sand t h a n i n loam and hence t h e s e h i n t  difference  soil  greater  t h a n when t h e same  reduction i n evaporation with longer intervals  much g r e a t e r primary  not  As e x p e c t e d , more w a t e r e v a p o r a t e d when  r e t a i n i n g c a p a c i t y of the s o i l s . more  i f the  t o p l a n t s i s d e t e r m i n e d by e v a p o r a t i o n and  water  intervals.  the  below  sand  s m a l l amounts w e r e a d d e d a t s h o r t i n t e r v a l s  was  and  t o t h e b o t t o m o f t h e r o o t zone a n d t h e n t h e amount o f  storage capacity.  amount  soil  on  from  I n s e m i a r i d c o n d i t i o n s most r a i n f a l l s do n o t  water a v a i l a b l e the  so  storage  evaporation. the  evaporate  Water  to  in  coarse  i n semi-arid or a r i d areas.  experiments  on  loam  soil  samples  and  showed  the  importance  transporting  soil  moisture.  to  move f r o m warm t o a c o o l e r  phases,  and the r a t e  F i c k ' s Law.  The  heat  the  area i n both l i q u i d  of transfer  and  moisture  flux  was  fluxes  calculated  difference.  t h e sum  by  The  applying  a  constant  pressure difference  the n e t heat  conductivity  of  was  5  cm.  a  of  water  transport  flow  soil  due t o  component  pressure  was  differences  Subtracting  The t e m p e r a t u r e t o b e much  f o r by the temperature soil  materials.  the  The  soil  larger  than  results  showed  moisture  through  a  suction  the s o i l  as a  At a suction of  g r a d i e n t was e q u i v a l e n t t o 2 5 0  I t was was  dependence  dependence o f t h e  °C/cm. a t a s o i l  temperature  p e r cm.  through  of  months.  and the second,  p r e s s u r e g r a d i e n t o f 2 cm. o f w a t e r p e r cm.  cm.  function  o f two c o m p o n e n t s , t h e  o f Hg moves a s much w a t e r  34 cm. o f Hg t h i s  t o measure t h e  f o r seven  gradient.  observed  temperature g r a d i e n t of 0.5 of  by  f l o w component f r o m t h e n e t f l u x gave t h e  flux  c o u l d be a c c o u n t e d  and vapor  & 34 cm o f Hg) w i t h a n d t h e n  f l u x due t o t h e t h e r m a l g r a d i e n t . of  taken  different  thermal  as  pressure  (suction gradients of 5,10,18,25 against  water  Unsaturated Columbian  due t o t h e p r e s s u r e d i f f e r e n c e thermal  in  i s more t h a n p r e d i c t e d  and t h e o b s e r v a t i o n s were  net moisture  first  gradients  Thermal g r a d i e n t s cause  and p r e s s u r e g r a d i e n t s .  was u s e d  thermal  The e x p e r i m e n t a l s e t up was b u i l t  simultaneous thermal  of  also  several  observed times  that  greater  vapor than  predicted air.  by F i c k ' s  For suction  transfer driven rate  pressures below  accounted  water  law of the d i f f u s i o n  f o r less  flux.  i s perhaps  due  18 cm. o f Hg,  than h a l f  The r e a s o n  are  much g r e a t e r  Cassel  into  this  f o r the h i g h vapor  vapor  transfer  of large microscopic  thermal g r a d i e n t s a c r o s s the a i r spaces thermal conductivity  vapor  of the net thermally  to the presence  the  water  of the s o l i d  i n the s o i l , and l i q u i d  that i s  components  than that ofa i r .  e t a l . (1969)  studied  the r e d i s t r i b u t i o n  of  soil  water w i t h i n i n s u l a t e d , u n i f o r m l y packed, h o r i z o n t a l samples o f unsaturated contents from  Columbia  i n response  0.5  to  1.0  fine  thermal  The  °C/cm.  Seasonal  greater  temperature  gradients  l i q u i d phases.  loam  at several  soil  t o imposed temperature g r a d i e n t s  temperatures t o depths crops.  sandy  that  than the r o o t i n g  variation  tend  fluctuations  with  depth  t o move w a t e r  water ranging  affect zones  gives  soil  o f most rise  i n both vapor  to and  L a b o r a t o r y i n v e s t i g a t i o n s have l i k e w i s e d e t e c t e d  soil  w a t e r movement i n r e s p o n s e t o t h e r m a l g r a d i e n t s .  and  Cary  (1960)  proposed  a  theory  based  on  Taylor  irreversible  t h e r m o d y n a m i c s f o r d e s c r i b i n g s o i l w a t e r movement i n r e s p o n s e t o temperature  gradients.  This  theory  placed  requirement t h a t t h e heat f l u x though t h e s o i l was m o d i f i e d i n a l a t e r the  use  of  the  b e known b u t i t  theory although both theories  soil-water-diffusivity  strict  coefficients.  involved  Soil  bulk  d e n s i t y "and i n i t i a l ,  transient  and f i n a l  s o i l . water  content  d i s t r i b u t i o n were d e t e r m i n e d each 0.5 cm a l o n g t h e column by gamma-radiation a t t e n u a t i o n . temperature  distributions  Initial, were  t r a n s i e n t and f i n a l  monitored  by  glass  soil  encased  t h e r m i s t o r s a t 2-cm i n t e r v a l s b o t h a t c e n t e r and 0.3 cm from t h e column w a l l .  The apparent t h e r m a l and i s o t h e r m a l  soil  water  d i f f u s i v i t y v a l u e s were c a l c u l a t e d u s i n g t r a n s i e n t water c o n t e n t data.  Several  investigators  observed t h a t  a specific  water  c o n t e n t o r range o f water c o n t e n t e x i s t e d a t w h i c h t h e maximum net  water t r a n s f e r f o r a g i v e n s o i l o c c u r r e d .  The o b s e r v e d n e t  water f l u x was found t o i n c r e a s e w i t h d e c r e a s i n g water c o n t e n t throughout t h e 0.077 t o 0.274 c u b i c cm/cubic  cm range.  For  Columbia s o i l a t 0.077 c u b i c cm/cubic cm t h e o b s e r v e d mean n e t w a t e r f l u x a c r o s s 1 cm s e c t i o n s o f t h e s o i l  showed agreement  w i t h t h e t h e o r y p r e d i c t e d by P h i l i p and d e V r i e s (1957) and by the  m o d i f i e d T a y l o r - C a r y law.  Soil  water  movement was  studied  by Haq  (1973)  i n the  l a b o r a t o r y u s i n g a p l e x i g l a s s box. The s o i l type he used was a Hawaiian c l a y of v o l c a n i c o r i g i n .  H i s study i n v o l v e d applying  water a t r a t e s o f 1.5, 4, 10, o r 16 cc/min f o r v a r i o u s d u r a t i o n s up  t o 90 m i n u t e s .  I t appears  that  water  ponding under t h e p o i n t o f a p p l i c a t i o n was n o t a problem.  This  was p r o b a b l y because hydraulic  conductivity  from h i s r e s u l t s  the duration high.  was  quite  His results  short  and t h e  showed t h a t  water  movement a n d w a t e r  c o n t e n t w e r e t h e same f o r e q u a l v o l u m e s  water a p p l i e d at d i f f e r e n t flow rates. wetted p r o f i l e s  had  a  w e t t e d f r o n t a n d was the  initial  move  soil  faster  slight  The w a t e r c o n t e n t i n t h e  gradient  from  the source  approximately equal to f i e l d  water  through  c o n t e n t was  the  soil  and  of  increased, attain  l e v e l as a s i m i l a r t e s t where t h e i n i t i a l  the  to  the  capacity.  If  the water  would  same s o i l  water  s o i l w a t e r c o n t e n t was  less .  Rahi the  effect  hydraulic water  ray  Jensen  o f t e m p e r a t u r e on v a r i o u s conductivity,  Dundee s i l t  t e c h n i q u e was  water  soil  water  loam s o i l  content,  diffusivity, was  water  used  I t was  temperature.  found in  to  was  measure  that  experiments  to  flow parameters diffusivity  and  study  such  as  specific  u s e d as i t c a n be  general  i n t h e v e r y wet  content  that is  with  hydraulic  an  by  temperature.  conductivity  water  increased  at  The  content as  a  packed  and  with  increase  The a  results given  t e m p e r a t u r e d e p e n d e n t and an i n c r e a s e  bulk  in  at  water  evident. a  given  hydraulic  indicated  water  of  increasing  not c l e a r l y  in diffusivity an  gamma  function  o f t e m p e r a t u r e on s o i l  r a n g e , was  increase  caused  on w e t t i n g .  diffusivity  However t h e e f f e c t  shown  conductivity the  conducted  u n i f o r m d e n s i t y and does n o t s w e l l  density.  It  (1975)  c a p a c i t y u s i n g s t e a d y s t a t e and p r e s s u r e p l a t e o u t f l o w  methods. to  and  that  content  i n conductivity with  is a  rise  i n temperature  viscosity from  could  o f the water.  be a t t r i b u t e d  Soil  water  to a decrease  c a p a c i t y i s determined  t h e s l o p e o f water c o n t e n t p r e s s u r e head c u r v e s  was  found  t o be independent  and  a t low water  in  o f temperature  and i t  near s a t u r a t i o n  contents.  Water movement s t u d i e s were conducted  i n the l a b o r a t o r y by  Hachum et a l . (1976) f o r two d i f f e r e n t s o i l types.  The two s o i l  types were a loamy sand and s i l t loam with bulk d e n s i t i e s of 1.62 and 1.4 gem" , r e s p e c t i v e l y .  Each s o i l was placed i n a narrow box  to  They observed that as the discharge  3  simulate a l i n e source.  increased, the depth of water movement decreased and the r a t e of h o r i z o n t a l movement i n c r e a s e d f o r equal amounts of water. suggested  They  that t h i s was a d i r e c t r e s u l t of the i n c r e a s e d ponded  area under the p o i n t of a p p l i c a t i o n . with the s i l t  T h i s was more n o t i c e a b l e  loam s o i l compared to the loamy sand s o i l .  When the  water a p p l i c a t i o n was terminated, the h o r i z o n t a l movement almost stopped, while the v e r t i c a l movement continued a t the same r a t e for  the loamy sand s o i l .  The v e r t i c a l movement a l s o continued a t  the same s t a t e when the a p p l i c a t i o n was terminated f o r the s i l t loam s o i l .  Bar-Yosef  and S h e i k h o l s l a m i  (197 6)  s t u d i e d water movement  i n the l a b o r a t o r y u s i n g a sandy s o i l and two d i s c h a r g e r a t e s of 0.25 and 2.5 l i t e r s per hour.  A volume of one l i t e r was a p p l i e d  for  e a c h f l o w r a t e a n d t h e w a t e r movement a n d w a t e r c o n t e n t  m e a s u r e d 48 h o u r s a f t e r found that the v e r t i c a l the  the i r r i g a t i o n  was t e r m i n a t e d .  rate  increased  indicated with after  movement i n c r e a s e d f r o m 13 t o 31 cm a n d  from  0.2 5  t o 2.5  increasing  flow  rate.  I t appeared  water content  compared t o t h e lower  Hachum e t a l . ( 1 9 7 6 ) ,  values  that  This  appreciably  redistribution  dimensional discharge  water  i n the higher  flow rate  movement  measured.  irrigation  comparison vertical  and s o i l  r a t e s were a p p l i e d t o loamy sand s o i l  were  to  horizontal  vertical.  advance  I t was  After  of the wetting  turning front  decreases,  given while  increase  attributed  volume  of water,  depth  the h o r i z o n t a l extent  i n application rate.  to the increase  i n width  and s i l t  loam  tensiometer during  was  the  due  o n two  Different  that  movement  l a r g e compare t o h o r i z o n t a l w a t e r advance. for a  type  f r o n t and  observed  water  rate  of rate of  distribution.  and t h e p o s i t i o n of the w e t t i n g  readings  the effect  source  and  flow  profile.  considered  water a p p l i c a t i o n from a t r i c k l e  after  p e r hour.  t h e a p p l i c a t i o n s l o w e d t h e h o r i z o n t a l w a t e r movement a n d  profile  soil,  liters  t h a t h o r i z o n t a l movement d i d n o t c h a n g e  r e s u l t e d i n lower  with  I t was  h o r i z o n t a l movement d e c r e a s e d f r o m 19.5 t o 15.5 cm a s t h e  flow  that  was  and  small  in  water o f f ,  to gravity  was  I t was a l s o shown of  wetted  of wetting  The r e a s o n of saturated  zone  increases  f o r this i s soil  strip  at  the surface  i n . the v i c i n i t y  two d i m e n s i o n a l  shape  of  the t r i c k l e  o f t h e w e t t e d f r o n t was  source.  The  a p p r o x i m a t e d as  a semiellipse.  L e v i n and van Rooyer studies  compared l a b o r a t o r y and  t o t h e m a t h e m a t i c a l model  (1971).  They u s e d a sandy s o i l  d e n s i t y o f 1.5 continuously  gem" . 3  and  increments. liters  (1979)  The  2  d e v e l o p e d by  liters  per  volume o f water  hour  pulsed  wetted  i n each  amount o f w a t e r  test  30  minute  a p p l i e d t o a l l t e s t s was  was  initiated.  determined  i n the wetted s o i l  u s i n g t h e m a t h e m a t i c a l model. t h i s c a s e was  and  in  12  a n d measurements o f s o i l w a t e r movement a n d w a t e r c o n t e n t  soil  liters  bulk  T h e i r t e s t s used f l o w r a t e s o f 2 and 4 l p h  amount o f w a t e r f o u n d i n t h e s o i l p r o f i l e was  in  et a l .  c o n t a i n i n g 98% s a n d a n d a  w e r e t a k e n 12 h o u r s a f t e r e a c h t e s t was of  Brandt  field  applied.  vertical  11.4  liters  Their  and 11.9  v o l u m e was  the  average  liters.  also  The  predicted  The a v e r a g e amount o f w a t e r f o u n d compared t o t h e a c t u a l amount o f 12  results  movement  T o t a l volume  indicated that  resulted  from  higher  greater flow  lateral emitters  c o m p a r e d t o l o w e r f l o w e m i t t e r s 12 h o u r s a f t e r t h e s t a r t o f e a c h test.  T h e y a l s o s u g g e s t e d t h a t g r e a t e r amounts o f w a t e r  be u t i l i z e d b y t h e p l a n t i f l o w o r p u l s e d  could  f l o w r a t e s were used  compared t o h i g h d i s c h a r g e  rates.  F u r t h e r t h e y recommended t h a t  lower  or high  flow  pulsed  flow  rate  would  emitters  result  rate  emitters  that  i n more w a t e r r e m a i n i n g i n t h e u p p e r  are soil  profile  t o be u t i l i z e d b y  Topp  al.(1982),  et  Reflectometry with  (TDR),  impedance  efficient  demonstrated  applied  to  discontinuities  measure  measure the  soil  evaporation  and  of s i l t  the p l a n t .  of  soil  water  water contents  that  Time  parallel  transmission  provide  an  content.  during  i n laboratory.  lines  effective TDR  was  and  used  infiltration,  to  drainage,  r i s i n g w a t e r t a b l e c o n d i t i o n s i n a 105  loam s o i l  domain  cm  column  T h r e e methods o f i n s t a l l a t i o n  o f t r a n s m i s s i o n l i n e s and  t h r e e types of t r a n s m i s s i o n l i n e s were  used  work.  i n the  experimental  six  transmission  and  one  the rods soil pilot The  lines,  five with  w i t h out d i s c o n t i n u i t y b)  using  a  guide  f o r the  hole  c)  soil  i s taken  transmission  lines  discontinuities  installed  discontinuities  observed r e g u l a r l y was  were  from  out  filled  air-dry  discontinuities  s o i l packed around  can  in  t o 90 cm  group  of  discontinuities.  The  method  be  grouped  as  dry  soil  b)  wet  soil  soil.  3  factor cm,  c)  not  a)  and  i t was  a  hole. with  lines lines  the  use  lines  Volumetric water  at various  with without content  shown t h a t For  the  the s t a n d a r d d e v i a t i o n s were  less  cm" .  The  lines  which  3  does  form of a p i l o t  f o r almost a year  to 0.02  the  this  i n the  with  a significant  or equal  rods,  i n s t a l l e d i n wet  d e p t h i n t e r v a l o f 10 than  having  used,  packed  location  soil  a)  s i x t r a n s m i s s i o n l i n e s pushed v e r t i c a l l y i n to  discontinuities  was  I n s t a l l a t i o n methods were;  largest  depths.  standard  included  the  deviations air  measurements of v o l u m e t r i c w a t e r  filled content  by TDR a n d g r a v i m e t r i c s a m p l i n g method d i f f e r e d b y ± 0.03 cm cm . 3  The  reason f o r t h i s discrepancy  in  soil  It  was a l s o  the  design  content Lines  c a n be a t t r i b u t e d t o v a r i a t i o n s  f a c t o r s such as d e n s i t y and w e t t i n g observed that of rods  values,  with  neither  or with  there  or drying  lines  was g o o d  changed  the water  electrical  o u t d i s c o n t i n u i t i e s gave  about water content v a l u e s ,  patterns.  t h e i n s t a l l a t i o n method n o r  of transmission  provided  3  contact.  t h e same r e s u l t s  e x c e p t when t h e r e was a n u n c e r t a i n t y  about t h e m a t e r i a l i n t h e u n f i l l e d d i s c o n t i n u i t i e s .  I t was a l s o  suggested that s o i l  l a r g e r than  that  expected  or a material with a d i e l e c t r i c  for soil  should  be  used  for filling  the  discontinuities.  Mostaghimi trickle  emitters  and  Mitchell  discharge  (1983)  rates  compared  systems.  This  t o the continuous  the e f f e c t  on t h e d i s t r i b u t i o n  m o i s t u r e i n a s i l t y - c l a y loam s o i l , irrigation  studied  under p u l s e d  laboratory  study  of  soil  and c o n t i n u o u s  indicated  applications, pulsed  of  that,  applications  r e s u l t e d i n s i g n i f i c a n t reduction i n water losses below the s o i l profile  under the h i g h  discharge  increasing  trickle  discharge  horizontal  component a n d i n c r e a s e  rates.  rate  found  r e s u l t e d i n decrease i n vertical  wetted s o i l p r o f i l e f o r both pulsed  Hopmans a n d Dane,  They a l s o  that  i n the  component o f t h e  and continuous a p p l i c a t i o n s .  (1985), s t u d i e d t h e t h e r m a l p r o p e r t i e s o f  soil  water  upper  part  isothermal  regime  that  of s o i l  have o f t e n been i g n o r e d .  profile  Although the  i s e a s i l y recognized  medium, t h e t h e r m a l e f f e c t s o n s o i l  t o be a non-  water regime i n  many o f t h e s o i l w a t e r movement s t u d i e s h a s b e e n m u t e l y The  soil  temperature  water  movement  regimes  was  for a  simulated  variety  of  under  initial  ignored.  different  and  boundary  conditions.  The c o r r e c t i o n s  for soil  hydraulic proprieties,  attributable  to  changes,  were  experimental theoretical  temperature  data  extracted  considerations.  considerations,  the  c o e f f i c i e n t of surface water pressure acquired  from In  multiples  the of  literature  case  of gradient  of pressure  more p r o n o u n c e d  found i n s o i l  f o r a pressure  condition at the s o i l  temperature  surface.  the s o i l  condition  surfaces  than  used.  where t h e  for a flux  boundary  The e f f e c t s o f t i m e a n d d e p t h i f hydraulic  properties  hydraulic properties  f o r simulating  to  w a t e r movement  d e t e r m i n e d a t t h e mean t e m p e r a t u r e o f t h e p r o f i l e . an i n d i c a t i o n t h a t  respect  The t e m p e r a t u r e e f f e c t s w e r e  head  t e m p e r a t u r e were m i n i m a l  laboratory  on  theoretical  head w i t h  The e f f e c t o f t e m p e r a t u r e o n s o i l  c h a n g e s i n t e m p e r a t u r e were l a r g e .  the  or  on  tension of water that i n turn a f f e c t the  e f f e c t was p a r t i c u l a r l y  varying  of  calculated  was f o u n d t o d e p e n d u p o n t h e t y p e o f b o u n d a r y This  either  head, were u s e d t o a p p r o x i m a t e t h e e x p e r i m e n t a l l y  values  temperature.  the  based  real  conditions  This  were gives  determined i n  must b e done a t  t e m p e r a t u r e s r e s e m b l i n g t h e mean t e m p e r a t u r e o f t h e s o i l  under  field  conditions.  The  temperature  movement become more p r o n o u n c e d of  effects  whether  reference  the  existing  temperature,  soil  as t h e t e m p e r a t u r e  s o i l water p r e s s u r e head i n c r e a s e s .  on  on  The  temperature  is  water  coefficient  results also above  or  the temperature at which  depend  below  the  the  hydraulic  p r o p e r t i e s are determined.  N a d l e r e t a l . ( 1 9 9 1 ) u s e d Time domain r e f l e c t o m e t r y for  simultaneous  (derived soil  from  measurement  the s o i l  electrical  different  of  conductivity  based  on  to  bulk soil  a direct  T h i s method w h i c h  and  water  other  in  similar  attenuation  content  measurements of s o i l  profiles  and  different  transmission  bulk  soil of  by  was TDR.  reflections,  shown by Topp e t .  published  dielectric  and  method  which  load  of  used  concepts  conductivity,  simulated coaxial  soil  the bulk  experiment  than the r e s u l t s  previously  resulted  and  T h i s w o r k p r o v i d e d a new  of  0,  content,  does n o t d e p e n d on m u l t i p l e  (two r o d s ) a n d  always  The  analyze  measurement  parallel  not  types.  electrical  showed b e t t e r c o r r e l a t i o n a l . (1982)  (from the  a  soil  time and a t t e n u a t i o n .  calculating  water  c o n s t a n t , 8)  G ,  line  e s t i m a t e s of  electrical  soil  f o r u n i f o r m and l a y e r e d s o i l  transmission  independent  travel  dielectric  conductivity,  transmitted pulse),  of  (TDR)  results.  Both  (three rod)  The  TDR  water content f o r l a y e r e d p r o f i l e s  were  accurate, especially  constants.  probes  when w e t  soil  was  overlying  dry  soil,  study time  due t o e r r o n e o u s  a l s o recommended should  sometimes  that  be measured  difficult  on  content  suitable  measurements,  identify,  Using  procedures  method  including  (TDR)  when  heterogeneous initiated  and  soil  the case  has  used  soil  a study  been  layered profiles.  water  thermic pulse  among  soil based  from  TDR  i n many  domain  reported  different-textured Dasberg  and curves  soils  and i n  Hopmans  (1992)  forsoil  water  types i n u n i f o r m and  Measurements were t a k e n i n t h e l a b o r a t o r y f o r (coarse-loamy, clay  Typic Xerorthent) and a  loam  soil,  mixed, n o n a c i d t h e r m i c (fine-silty  u s i n g a two-rod  three-rod  coaxial  wet a n d d r y s o i l  the influence of v a r i a t i o n s  the s i g n a l .  content  content by time  successful  to obtain calibration  and a Yolo  transformer  study  methods o f  arise with regard to the v e r s a t i l i t y of  c o n f i g u r a t i o n s o f 5-cm-thick to  not at the  of layering.  water  profiles.  sandy loam  Xerorthent)  i s  e t . a l . (1984) a r e  c o n t e n t d e t e r m i n a t i o n s b y TDR f o r two s o i l  a Hanford  travel  p o i n t , which  usually  of Dalton  for calculating  studies, questions s t i l l the  the pulse  two i n d e p e n d e n t  A l t h o u g h measurement o f s o i l reflectometry  cases  The  d e t e r m i n a t i o n , i t was s h o w n t h a t m e t h o d s  the calculation  most  i n such  o f TDR d a t a .  at the i n f l e c t i o n  to  m i n i m u m o f TDR t r a c e . water  interpretation  i n soil  mixed,  nonacid  parallel  probe.  Typic  with  Different  l a y e r s were t e s t e d water  content  on  The c a l i b r a t i o n d a t a o f t h e c o a r s e - t e x t u r e d H a n f o r d  soil  matched t h e e s t a b l i s h e d  users. were  calibration  The d i e l e c t r i c c o n s t a n t s significantly  lower  water-content values. dielectric  constant  than  Results  of the fine-textured Yolo those  of the Hanford  s o i l water content i n f i e l d p l o t s , but a p p l i c a t i o n s t o  s t u d i e d and d e s c r i b e d .  R i c h a r d s o n e t a l . (1992)  three  closed-container,  moisture  levels  and  have  dictate  watering  TDR was a n e f f i c i e n t  water. Also,  estimation  method  different soil  and 0.98 types,  adequately  u s e d TDR method to monitor  schedules.  soil  In  f o r monitoring  a l l soil  o f s o i l w a t e r c o n t e n t b y TDR was h i g h l y  correlated to gravimetric analysis of s o i l 0.96,  n o t been  greenhouse s t u d i e s  experiments,  0.84,  equal  (TDR) h a s - b e e n w i d e l y u t i l i z e d t o  experiments  of  at  i n d i c a t e d t h a t bound w a t e r has a  controlled-environment  in  soil  close to that of i c e .  Time d o m a i n - r e f l e c t o m e t r y estimate  c u r v e a p p l i e d b y TDR  f o r the three  cores,  studies.  with r  2  values  They f o u n d  that  w i t h v a r i a b l e p h y s i c a l p r o p e r t i e s and b u l k  densities,  h a d no a p p a r e n t e f f e c t o n e s t i m a t i o n s  of s o i l  content.  Their  be u s e f u l i n  conclusion  greenhouse s t u d i e s  that  TDR  content.  i n v e s t i g a t e d t h e a p p l i c a b i l i t y o f TDR  measuring the water content of organic  TDR c a l i b r a t i o n was c o n d u c t e d bark,  could  t o a c c u r a t e l y determine s o i l water  A n i s k o e t a l . (1994) for  was  water  media i n c o n t a i n e r s .  f o r sand, p e a t ,  composted  sand and peat mix, sand and bark mix, and a  pine  commercial  growing  medium  volumetric  (Metro  water  3 00) .  Mix  content  was  Regression  conducted  apparent: p h y s i c a l l e n g t h of the probe variable. to  with  analysis the  (La:L) as a n  ratio  of  independent  c a l i b r a t i o n c u r v e f o r M e t r o M i x 3 00 was  The  of  compared  c u r v e s g e n e r a t e d f o r a range of s o i l s by o t h e r i n v e s t i g a t o r s .  A d d i t i o n a l l y , w a t e r c o n t e n t and La:L changes were m o n i t o r e d i n Metro  300  Mix  f o r 10  months  and  were  v a l u e s from the c a l i b r a t i o n curve. water that  content than sand Equations 1992)  Hopmans,  compared w i t h  compared  developed  by  generally  underestimated  attributed  this  difference  previous  decomposed  organic  matter  curve to  or  p r e s e n c e o f more b o u n d w a t e r .  a  predicted  Organic media had a h i g h e r  f o r t h e same L a : L  the c a l i b r a t i o n  to  value.  authors  large  when  300.  They  Mix  and  and  content  fraction  vermiculite  found  (Dasburg  water  f o r Metro  They  of  highly  thus,  to  the  S p e c i f i c c a l i b r a t i o n o f TDR  may  be r e q u i r e d t o d e t e r m i n e t h e a b s o l u t e w a t e r c o n t e n t o f o r g a n i c growing  media.  P l a n t s g r o w i n g on s t o r e d s o i l w a t e r o f t e n e x h i b i t of  symptoms  w a t e r d e f i c i t even t h o u g h a r e l a t i v e l y l a r g e q u a n t i t y o f  water  i s available  subsoil.  To  absorption  where r o o t s  e x p l o r e the p o s s i b i l i t y phenomenon  distribution Ritchie  f o r uptake  or  (1995)  root  that  was  related  to  clumping  around  soil  examined  the  soil  are present i n the this  suitability  less  effective  nonuniform peds. of  Amato  root and  time-domain  r e f l e c t o m e t r y f o r measuring s o i l a small spatial scale.  water content  M e a s u r e m e n t s were made o n c l a y l o a m a n d  s a n d y c l a y s o i l s w i t h 21mm l o n g p a r a l l e l lines  d i s t r i b u t i o n on  balanced  transmission  and compared w i t h g r a v i m e t r i c w a t e r c o n t e n t  measurement.  Water content  values  ranged from oven d r y t o s a t u r a t i o n .  quantify the error i n propagation  t i m e measurement  transmission  were  lines,  measurements  l e n g t h s r a n g i n g f r o m 10 t o 150 mm. was q u i t e h i g h soil.  In this  For  longer  times,  soil  case,  the technique  corresponding  contents  measuring  transmission line  proved  less  t o higher water  >0.29  values of d i e l e c t r i c constant. in  i n a i rusing r o d  The c o e f f i c i e n t o f v a r i a t i o n  o f v a r i a t i o n was <3%.  w i t h water  effective  short  ( 2 . 8 - 7 . 3 % ) f o r times s h o r t e r than 100 ps f o r a i r -  dry  coefficient  made  using  To  reliable.  contents, the  A few samples o f c l a y  m  3  irf  showed  3  loam  excessively high  Time-domain r e f l e c t o m e t r y p r o v e d  water  content  f o r values >0.07 m  3  with  the  tested  m" . 3  P e p i n e t a l . ( 1 9 9 5 ) u s e d t i m e d o m a i n r e f l e c t o m e t r y TDR f o r d e t e c t i n g and q u a n t i f y i n g the e f f e c t of temperature apparent  d i a l e c t i c constant.  developments Prior  i n the f i e l d  to this  w i d e l y used t o determine dielectric  constant  T h i s was f a c i l i t a t e d b y t h e r e c e n t  o f time  application,  d o m a i n r e f l e c t o m e t r y (TDR).  electromagnetic  the water content  of water  on t h e s o i l  i s larger  measurements  of s o i l s  than  were  and as t h e  t h a t o f any s o i l  c o n s t i t u e n t s any change i n t h e m i x t u r e o f s o l i d s ,  a i r and water  p r e d o m i n a n t l y r e f l e c t s change i n w a t e r c o n t e n t . errors with  associated  with  the s o i l  t e m p e r a t u r e on a range  types  examined  were  sand,  apparent  of s o i l s loam,  The measurement  dielectric  constant  were examined.  and peat  The  and each  of  soil these  measurements were done a t s o i l w a t e r c o n t e n t s i n a r a n g e o f 0 . 0 9 to  0.81  c u b i c meters  showed r e s e m b l a n c e literature.  p e r c u b i c meter.  on c o m p a r i s o n w i t h  In the s o i l s ,  The m e a s u r e d the figures  h i g h e s t changes  variation  reported i n  i n the apparent  d i e l e c t r i c c o n s t a n t w i t h t e m p e r a t u r e were o b s e r v e d a t h i g h w a t e r content values.  The s o i l s n e a r s a t u r a t i o n u n d e r w e n t  changes i n  d i e l e c t r i c c o n s t a n t w i t h r e s p e c t t o t e m p e r a t u r e much l o w e r t h a n predicted  by t h e m i x i n g model.  These  results  indicate  that  t e m p e r a t u r e dependence o f d i e l e c t r i c c o n s t a n t o f w a t e r i n a matrix  i s lower than that  textured  and  organic  of b u l k water, p a r t i c u l a r l y  soils.  The  soil  i n fine  experimentation  clearly  i n d i c a t e d t h a t t e m p e r a t u r e has a s m a l l b u t s i g n i f i c a n t e f f e c t on the  c o m p o s i t e d i e l e c t r i c c o n s t a n t o f wet s o i l s .  account  f o r changes  especially  i n soil  at high soil  water  temperature  The f a i l u r e t o  can lead  consents.  to  The e f f e c t  t e x t u r e on d i e l e c t r i c p r o p e r t i e s o f wet s o i l s w a r r a n t s  errors  of  soil  further  investigation.  Lambany e t a l . ( 1 9 9 6 ) to  estimate s o i l  production,  c a r r i e d out t r i a l s  i n Quebec, Canada,  water requirements i n container tree  realizing  that  t h e development  of large  seedling seedling  c u l t i v a t i o n a n d t h e u s e o f a i r - s l i t c o n t a i n e r s h a v e made n u r s e r y irrigation  more  complex.  In  order  to  improve  irrigation  management, t h e y e v a l u a t e d t h e u s e o f t i m e d o m a i n r e f l e c t o m e t r y (TDR) e q u i p m e n t t o measure t h e v o l u m e t r i c c o n t e n t o f s u b s t r a t e s . Trials used  c a r r i e d o u t showed t h a t t h i s t y p e o f e q u i p m e n t c o u l d be  to  measure  Comparison  with  substrate measures  g r a v i m e t r i c a l l y confirmed  water  of  content  soil  water  in  real  content  time. determined  t h a t measurements o b t a i n e d b y TDR  are  very precise.  Young e t a l . (1997) p r o p o s e d a n u p w a r d i n f i l t r a t i o n which i s rapid, experiment,  a l l o w s the s o i l t o remain unchanged d u r i n g t h e  and p r o v i d e s hundreds of d a t a p o i n t s , t o c a l i b r a t e  a t i m e d o m a i n r e f l e c t o m e t r y (TDR) experiments  soil  contents.  total). with  soil  at  data  from  the  two  The  constant-water  of three textures  a l s o were p e r f o r m e d  by  progressively higher  water  methods  using  were  fitted  t o two p u b l i s h e d m o d e l s o f t h e d i e l e c t r i c  of a l l three s o i l s ,  r e p l i c a t e experiments,  were s i m i l a r  the r e p l i c a t e experiments and  was  f i t t e d simultaneously to  i n shape and  A s i n g l e c a l i b r a t i o n curve,  equation  three  c o n t e n t r e l a t i o n s h i p . The r e s u l t s showed t h a t t h e  c a l i b r a t i o n curves  Topps  Calibrations  cores  r e g r e s s i o n techniques  t h e same.  system. They c o n d u c t e d  u s i n g 18.7-cm-long p r o b e s i n s o i l s  (nine experiments packing  method  f i t t e d simultaneously to  of the three s o i l s , statistically  statistically  the  was c o m p a r e d w i t h same.  The  results  support  the  provides  a  conclusion fast  and  that  the  upward  infiltration  repeatable c a l i b r a t i o n  method  method c o n s i s t e n t  with conventional calibration.  D e - S i l v a e t a l . (1998) horticulture.  r e a l i z e d t h e p o t e n t i a l u s e o f TDR  They d e t e r m i n e d  TDR  c a l i b r a t i o n curves  for tuff  ( g r a n u l a t e d v o l c a n i c a s h ) , v e r m i c u l i t e , p e r l i t e and a m i x o f composted a g r i c u l t u r a l wastes  ( g r a p e marc, s e p a r a t e d cow  and  these m a t e r i a l s which  also  used  as  tested,  tested  the mixes of  horticultural measured  substrates.  calibration  l i n e a r equations throughout cover  the  (Ledieu well  working  et  range  a l , 1985),  For  results  were  i n horticulture.  w i d e l y used  in soils,  the measured r e s u l t s f o r p e r l i t e ,  bound water)  pores).  The  and  tuff  described  u s e d due  W i l d e n s c h i l d and J e n s e n u n s a t u r a t e d f l o w and  equation  described  (because of t h e to water  by  content that  Ledieu's  in  fairly those  presence occluded erroneous  n e c e s s a r y whenever a  new  t o the d i f f e r e n c e s o b t a i n e d between  t h e m e a s u r e d c a l i b r a t i o n e q u a t i o n s and L e d i e u ' s  controlled  are widely  s t u d y c o n c l u d e d t h a t i n o r d e r t o a v o i d an  s u b s t i t u t e was  manure)  but underestimated  ( p r o b a b l y due  i r r i g a t i o n management, c a l i b r a t i o n was soil  well  two  substitutes  t e s t e d values of water  o b t a i n e d f o r o r g a n i c media, v e r m i c u l i t e of  a l l soil  in  (1999)  investigated  equation.  two-dimensional  t r a n s p o r t through heterogeneous  laboratory conditions.  The  unsaturated  sand  under  hydraulic  c o n d u c t i v i t y of  f i v e homogeneous s a n d s and  s y s t e m s composed o f t h e s e f i v e s a n d s was state  f l u x c o n t r o l l e d method.  The  were e s t a b l i s h e d i n a l a b o r a t o r y random  d i s t r i b u t i o n s of  s y s t e m o f 207  grid cells.  upper boundary, w h i l e such  that,  the  on  established  the  and  average,  a  flow  transport  as w e l l as dye  took place  to  tortuosity tortuous hydraulic three  be  d e p e n d e n t on  increased  with  flow patterns,  effective  degree  decreasing  breakthrough time domain  where  and  several  degree of t o r t u o s i t y of  saturation,  saturation.  found t h a t the the  was  as  the  Despite  the  e f f e c t i v e unsaturated  r e t e n t i o n curves f o r  the  an  t h i s type of heterogeneous f l o w system  equivalent  homogeneous medium c h a r a c t e r i z e d  can by  parameters.  Phogat  of  the  pattern  The  the  r e a l i z a t i o n s of the heterogeneous sand were q u i t e s i m i l a r ,  t r e a t e d as  axial  Solute  tortuous  c o n d u c t i v i t y as w e l l as  thus suggesting that be  we  profile  t r a c e r p a t h s , showed t h a t f l o w  i n a very  a  lower boundary  i n the tank u s i n g  g r i d c e l l s were c o m p l e t e l y bypassed. appeared  systems  comprising  pressure  applied.  steady  c o n t r o l l e d at  a p p l i e d at the uniform  sand  a  r e a l i z a t i o n s of  sands  w a t e r f l u x was  c u r v e s measured a t d i s c r e t e p o i n t s reflectometry,  heterogeneous  homogeneous  The  heterogeneous  measured u s i n g  tank f o r three  s u c t i o n was  gravity  three  et  al.  tomography  (1991)  (CAT)  w a t e r c o n t e n t and  enunciated  the  f o r measurement o f bulk  density.  use  of  computerized  spatial distribution  P r i o r to  this  application,  CAT s c a n n e r was u s e d t o measure s p a t i a l c h a n g e s i n s o i l d e n s i t y . Subsequently  CAT s c a n n i n g h a s b e e n a p p l i e d u s i n g s i n g l e  x - r a y o r gamma r a y a t t e n u a t i o n t o m e a s u r e t h e s p a t i a l in  water  content  limitation measuring  i n proximity  of single spatial  r a y x-ray  distribution  to plant  roots.  energy  variation  One  of the  o r gamma r a y CAT s c a n n i n g f o r o f water  assumes a u n i f o r m b u l k d e n s i t y .  content  i s that i t  Attenuation i s a function of  b o t h b u l k d e n s i t y and water content. I n order t o monitor  changes  i n both s p a t i a l  content  d i s t r i b u t i o n o f bulk d e n s i t y and water  we n e e d a s i m u l t a n e o u s u s e o f two e n e r g y  s o u r c e s a n d gamma r a y s  w e r e p r e f e r r e d a s m o n o c h r o m a t i c beams a r e r e a d i l y  available.  CAT  gamma r a y  was  applied  attenuation spatial  to dual  i n soil  columns  distributions  d e n s i t y f o r two, s o i l degrees. pixel  between  were  t h e two t y p e s  1 3 7  Cs  and  t o determine  of volumetric  1 6 9  Yb,  nondestructively the  water  content  and b u l k  types that e x h i b i t s w e l l i n g t o d i f f e r e n t  The beam s l i c e  dimensions  source,  t h i c k n e s s was m a i n t a i n e d a t 2 mm a n d  2mm  b y 2mm.  of s o i l  The p r i n c i p a l  was t h e h i g h e r  difference  silt  and c l a y  c o n t e n t i n York s o i l and a dominant c l a y m a t e r i a l o f s m e c t i t e i n York  and k a o l i n i t e  for  average  water  i n the Kulin s o i l . content  and bulk  The CAT s c a n n i n g m e t h o d density  provides  agreement w i t h t h e v a l u e s o b t a i n e d g r a v i m e t r i c a l l y . in  t h e mean  and standard  deviation  of pixel  following wetting are related to texture, and  good  The c h a n g e s bulk  structure,  C a l c i u m and/or Sodium exchange s t a t u s o f s o i l .  density  mineralogy Systematic  e r r o r s a r i s i n g f r o m random n a t u r e o f r a d i o a c t i v e e m i s s i o n s , count  times  deviation uniform  of  of  the  field  individual approach  2  water  very  ray  to  seconds,  content  large  sum  and  steady  resulted  s t a t e or  of  soil  even  content,  dry are  counting  standard  soils. required  times  s l o w l y changing  For for  limit  systems.  to dual energy l e v e l  t o become a m a j o r t o o l  water  significant  times  large  w h i l e t h e a p p l i c a t i o n o f CAT the p o t e n t i a l  for  counting  such  in  for  Thus,  scanning  has  for nondestructive studies  structural  2.3  status  and  stability,  et  infiltration results.  electronics.  al.  from  As  (1971)  a  compared  trickle  a p a r t of  f l o w model.  computed r e s u l t s and  experimental  water  with  those  of  the  experimental  verifications, to the  loamy  sand  c o n d i t i o n s of  two-  made b e t w e e n t h e  o b t a i n e d from a f i e l d to those  transient  t h a t has  been  of c y l i n d r i c a l  flow  f u n c t i o n a l r e l a t i o n s h i p between water d i f f u s i v i t y  content  was  estimated  using  a  computer  complements the c o n v e n t i o n a l d i f f u s i v i t y study  theory  A n o t h e r c o m p a r i s o n was  t r i c k l e d under c o n d i t i o n s s i m i l a r m o d e l . The  the  source  t e s t e d under c o n d i t i o n s s i m i l a r  dimensional  This  of  Mathematical Model S t u d i e s  Bresler  was  counting  an  this  r e a l i z a t i o n of t h i s p o t e n t i a l needs advancement i n t h e f i e l d s c a n n i n g geometry and  a  indicates that  despite  technique  determination  and that  method.  d i s c r e p a n c i e s between  the  experimental rates, the  and t h e o r e t i c a l r e s u l t s ,  e s p e c i a l l y a t low  trickle  the coherence i s s u f f i c i e n t f o r p r a c t i c a l a p p l i c a t i o n s of  theory.  The  study  also  gives  the  probable  reasons  d i s c r e p a n c i e s i n some c a s e s s u c h as i n a d e q u a t e a s s u m p t i o n s , of p r e c i s i o n i n e s t i m a t i o n of s o i l water parameters, boundary  condition  infiltration  definition  process.  stages  causing  the  results. trickle  and  possibly  i t becomes  discrepancy  discharge  an  These s o i l  between  to  the  i s small.  the  f o r m due t o t h e  ascertain  observed  and  the  factor  theoretical  w e t t e d a r e a and  increase  in  a c c o u n t e d by  a decrease  trickle  i n depth of wetted  discharge  the e f f e c t  R i s s e and Chesness (1985)  method  source  emitter.  rate.  of t r i c k l e  discharge This  (1989) s i m p l i f i e d D a s b e r g wetted  reduced  the  e m i t t e r f l o w r a t e , and  soil  The  This  predicted results  soil  can  be  rate  on  z o n e becomes  rate.  f o r p r e d i c t i n g the They  when  The r e s u l t s show an i n c r e a s e i n t h e  larger with increase i n t r i c k l e  only.  during  e s p e c i a l l y i n the  t h e s i z e o f t h e w a t e r e n t r y s a t u r a t e d zone.  texture,  inaccurate  c o n d i t i o n s a r e more  i n theory  hard  lack  However, i n g e n e r a l , h y s t e r e s i s becomes p r o m i n e n t  horizontal with  surface.  than those d e a l t w i t h  initial  hysteresis  The h y s t e r e s i s e f f e c t may  c o n d i t i o n s at the s o i l complicated  and  for  from  radius  required  and B r e s l e r ' s from  inputs  a to  point soil  water d e p l e t i o n p o t e n t i a l  this  s i m p l i f i e d method were  w i t h i n -19% a n d 1 1 % o f t h e m e a s u r e d v a l u e s .  Angelakis area  of  et  prediction  circular  trickle  time-dependent element  model,  of  have  efficient  system,  two-dimensional  showed shape  that of  the  linearized the  for  (1998)  model  and  loam  fronts  for clay  underestimation i n The  soil,  are  Yolo  possible  The  by  loam  or  sand,  Both  the  important of  a  The  predictions  done  for  trickle to  get  results of  the  numerical  and  Predictions  sandy  with  profiles  were  c o m p o n e n t , h o w e v e r t h e r e was the  vertical  reason  component  of  f o r d i s c r e p a n c y can  t h e i n a d e q u a c y o f t h e a s s u m p t i o n t h a t K e>  was  an the be  a unique  linear  P r e d i c t i o n s w i t h n u m e r i c a l s i m u l a t i o n were  better  (  function.  and  management  fronts,  over  front.  solution.  i n two-dimensional  distribution.  homogeneous  f o r the h o r i z o n t a l  and  hemisphere  characteristics.  water  advancing  finite  equation  the e x p e r i m e n t s were p e r f o r m e d  soil  the  clay  wetting  operation so  a  f r e q u e n c i e s and d i s c h a r g e r a t e s  textual  adequate  wetting  generalized  model were r e a s o n a b l y p r e c i s e .  linearized  or  flow  r a d i u s o f a wet  for Yolo  vertical  design,  irrigation  water  effective  different  measured  and  theory,  soil-water distribution  different  horizontal  infiltration  transient  Warrick  p r o f i l e s under  which  a  and  were  the  as  to  distribution,  in  source, using numerical techniques such linearized  water  work  a  f r o n t and  water  soil  methods l i k e  Healy  wetting  of  d i d comprehensive  under  solution  analytical  soil  a l . (1993)  than with the  l i n e a r i z e d model,  vertical  direction.  overestimated effective  the  However  horizontal  vertical  front,  distorting  front  and  f o r b o t h the  the  spherical  under  low  application  hand,  the  H e a l y and  to  between  attributed condition tensions higher  to  the  computed  than  by  slightly The  and  as  long  the  times.  horizontal  a  using  the  with  clay  possible  the  disc  but  Measured s o i l  finite  can  errors be  the  The  point  soil  water  solution  model  were  showed  water c o n t e n t s were  than those predicted better  for  source i s i n the  linearized the  However horizontal  reason  source.  the  the  results  showed  especially  soil.  in  by  these  models.  f o r c l a y loam t h a n f o r  sandy (  size  application rates  of  the  surface  f o r l i n e a r i z e d and  source  used  the also  t h e r e e x i s t s a b e t t e r a p p r o x i m a t e l i n e a r f u n c t i o n K ej  varying  in  other  model  diagonal positions,  measured  as  On  (1988) g e n e r a l i z e d  The  and  r e s u l t s were g e n e r a l l y  soil a  greater  the  were o b s e r v e d  those observed,  opposite estimation.  , under-predicted  especially  soil.  than  1 / 3  visible,  assumption that  rather  wet  was  overpredictions  calculations  the  symmetry  Warrick  clay  of  radius  gravity  rates  for  The  e f f e c t of  under  directions  soil.  the  sandy  model  The  and  significant  in  in  soils.  rates  application  t  especially  numerical  over-predicted  good agreement i n v e r t i c a l high  the  i n which  expands p r o p o r t i o n a l  wetting  soils,  component  hemisphere model,  hemisphere  wetting  f o r both the  between  n u m e r i c a l models.  and two  Dirksen  and Dasberg  relationship soil  suitable  (1993)  obtained a single  f o r c a l i b r a t i o n purposes  for  They compared t h e r e s u l t s  different  soils  soils,  with different  comparison (1980)  obtained  was  clay  made  contents  between  with a theoretical  (fitting  by  water  content  empirical  and  types  calibration  equation  and an  this  for a l l soils  d e n s i t y , t e x t u r e , temperature  work an e m p i r i c a l  e q u a t i o n was  p a r a m e t e r a, w h i c h with  c) f r e e w a t e r  relation  to  accounts the  empirical  low  bulk densities bound  water  higher water  and  salinity. by  curve-  applied  field.  The  results  for soils  (1.35  -  1.5  with g  cm"  T o p p ' s e q u a t i o n a p p e a r t o b e m o r e due t o associated with fine  with  a  low d i e l e c t r i c  equation takes care of both the Maxwell's  as i t does n o t  f o r the geometry of the  low c l a y c o n t e n t s and t y p i c a l b u l k d e n s i t i e s D e v i a t i o n s from  a)  a n d d) a i r .  developed  showed t h a t Topp's e q u a t i o n gave v a l i d r e s u l t s  ).  of The  c o m p o n e n t a) m i x i n g m o d e l f o r t h e f o u r c o m p o n e n t s  consider the s o i l  to  only  and b u l k d e n s i t i e s .  (Maxwell-Deloor)  Topp's e q u a t i o n i s n o t s u i t a b l e  medium  different  Topp's  s o l i d p h a s e b) t i g h t l y b o u n d w a t e r  fitting  of s o i l  e q u a t i o n s . R e s u l t s were compared f o r 11  theoretical  3  involving  p r o p e r t i e s t h a t a r e a l r e a d y known o r c a n be a c c u r a t e l y  calculated.  In  empirical  of these  textured soils constant.  issues.  Maxwell's  The r e s u l t s  e q u a t i o n do n o t m a t c h w i t h t h o s e o f TDR contents, p a r t i c u l a r l y  than  for irregular  of  data at  soils.  The  reason  for this  may  be  equation are not v a l i d of  the total  sensitive  that  the  of  Maxwell's  i f w a t e r o c c u p i e s more t h a n one  volume.  to  the assumptions  The m o d i f i e d e m p i r i c a l  unpredictable  value  of  a  third  equation i s and  can not  accommodate anomalous b e h a v i o r .  2.4  Knowledge Gap Based  o n my  intensive  literature  review,  I  found  s t u d i e s on t h e r m a l l y i n d u c e d m o i s t u r e movement i n s o i l s . all  s t u d i e s were i n l a b o r a t o r i e s  and s o i l s  i n closed  None o f them h a d s i m u l a t e d t h e f i e l d c o n d i t i o n s l i k e techniques  (surface,  trickle,  sprinkle,  some Almost  columns. irrigation  e t c . ) and t h e a p p l i e d  w a t e r movement a n d s t o r a g e w i t h i n d i f f e r e n t d e p t h s o f r o o t The  water  and n u t r i e n t  depths o f r o o t  distribution  and s t o r a g e i n d i f f e r e n t  zone i s i m p o r t a n t a s t h e r o o t d i s t r i b u t i o n  v a r i e s i n d i f f e r e n t depths.  zone.  also  The p r e v i o u s s t u d i e s w e r e d e s i g n e d  t o s t u d y t h e t r a n s f e r a n d movement o f w a t e r i n s o i l s a s a f f e c t e d by temperature  gradients.  Since a l l effect  s t u d i e s have i n d i c a t e d t h e p r o m i n e n t  on s o i l  further  water  movement,  explore the temperature  conditions. movement important  As  the s o i l  and d i s t r i b u t i o n  the author effects  water patterns  t o study the temperature  textured s o i l s .  and  felt  t h e need  simulating  dissolved  will  temperature  be  effect  the  to  field  agrichemical  t h e same,  i t was  i n coarse and  fine  F u r t h e r m o r e , s u r f a c e i r r i g a t i o n method i s most  widely  used  irrigation  including  that  Pakistan,  where  addition,  The  technique  i n the author's he  intends  World  Bank  to  the farmers  irrigation popularity  in  home P r o v i n c e o f  to  has  P r o j e c t and has been p r o v i d i n g  practiced  work  after  started  a  financial  forms  graduation.  Trickle  range  In  Irrigation  and t e c h n i c a l  of m i c r o - i r r i g a t i o n )  t h e r e . The t e m p e r a t u r e  world  Balochistan,  o f the p r o v i n c e . Because o f t h a t ,  (and o t h e r  the  support  the  trickle  is  getting  (30-40 °C)used i n t h i s  s t u d y i s h i g h e r t h a n t h o s e used i n any s t u d i e s r e p o r t e d as is  the normal  Balochistan. fine  range  The  and course  of  unique  temperature combinations  textured soils  that  this  i s encountered  of higher  in  temperatures,  and i r r i g a t i o n methods u s e d i n  t h i s s t u d y i s a i m e d a t f i n d i n g t h e p r a c t i c a l r e s u l t s t h a t c a n be applied  i n the f i e l d s  such  the northwestern  as  Egypt.  i n Balochistan India,  and o t h e r s i m i l a r  northwestern  China,  areas  Iran  and  CHAPTER I I I MATERIALS AND METHODS Studies under  t o determine water  surface  and  distribution  micro-irrigation  patterns  systems  at  i n soil different  t e m p e r a t u r e s were c o n d u c t e d i n t h e l a b o r a t o r i e s o f t h e C h e m i c a l and B i o l o g i c a l E n g i n e e r i n g Department. were  f o ran onion  Pakistan. from  crop  grown  The c o n d i t i o n s s i m u l a t e d  i n the Balochistan  The m a j o r i t y o f o n i o n s a r e grown i n s a n d y l o a m  March  to July  i n upland  Balochistan,  where  commonly b r o a d c a s t s e e d e d a n d f l o o d i r r i g a t e d , a 25-30 day i n t e r v a l . covers almost h a l f conditions, very  of Pakistan's area.  conditions  annually.  u s i n g a s much a s  The  having only eastern  part  of arid 1 0 0 mm of  climatic  plateau  with  (4 i n c h e s ) o f  the province i s  system.  Design o f Study For  loam)  this  were  Vancouver, x  onion i s  I t has unique  consisting  i r r i g a t e d by a well-developed canal 3.1  soils  The s o u t h w e s t e r n P r o v i n c e o f B a l o c h i s t a n  the western part  d r y weather  rainfall  Province of  80  cm) ;  experiment.  study,  obtained  two t y p e s from  a  B r i t i s h Columbia. one  f o r each  of s o i l selected  (sandy farm  Two wooden b o x e s type  The d i m e n s i o n s  of s o i l  o f t h e boxes  was  loam  and s i l t  i n Delta  near  ( 1 0 0 cm x 1 0 0 cm used  were  f o r this  based  on t h e  r o o t i n g d e p t h o f o n i o n s a n d some o t h e r v e g e t a b l e c r o p s g r o w n i n  Balochistan.  Another  experimental  soil  b o x e s was  M o i s t u r e Point™ p r o b e s , from  the  joints and  last  of  screens  diameter  to  designing  moisture  measured.  The  measurement  corner  h o l e s were d r i l l e d  drainage.  stop  l e t the water  the  The  soil  and  ranges  B l i e s n e r , • 1990;  bottom  to avoid  leakage  i n the bottom  dropping  out  of  with  from  the  drain.  from  F AO,  30-60  1990;  and  onion r o o t system i s found the growing  1990).  i n the  cm  (Gulik,  top  1989;  ASCE, 1 9 9 0 ) .  i n t h e t o p 18  season (Brewster,  roots are  Bliesner,  1994) 60%  of  cm  Keller  A b o u t 90% of s o i l  the s o i l  soil  with  (irrigation) condition.  a  (figure  and The  bubble flood  the  profile  the  (Keller  &  vertical  segments  of  3.1).  i n t h e b o x e s was long  of  80% o f  B a s e d on t h e s e s t u d i e s , 15 c e n t i m e t e r  the o n i o n r o o t zone  and  throughout  and a p p r o x i m a t e l y  segments were s e l e c t e d t o b e s t r e p r e s e n t d i f f e r e n t  plane  space  h o l e s were c o v e r e d  from  by-  r o o t i n g d e p t h o f o n i o n a t m a t u r i t y , as m e n t i o n e d i n t h e  literature,  The  the  w h i c h r e q u i r e s an a d d i t i o n a l 10 cm  to f a c i l i t a t e  holes but  feeder  soil  in  the boxes were s e a l e d w i t h s i l i c o n  each box  The  the  segment t o be  1 centimeter  plastic  consideration  level  leveled before  irrigated  l e v e l i n g was  to  to provide  t o a smooth the  start  bring  i t  the best  horizontal  of to  each a  run  uniform  situation  for  s y m m e t r i c w e t t i n g f r o m t h e p o i n t o f a p p l i c a t i o n t o be as c l o s e as possible geometry.  to the  simplifying  assumptions of  symmetrical  wetting  Figure  3.1  Typical rooting  root d i s t r i b u t i o n depth.  along  the  S o i l p r o p e r t i e s l i k e b u l k d e n s i t y and f i e l d c a p a c i t y 3.1)  were d e t e r m i n e d i n o r d e r  water t o be a p p l i e d and f l o w  Table  3.1  Physical  Sand (%)  Soil Type  t o c a l c u l a t e t h e t o t a l volume o f rate.  c h a r a c t e r i s t i c s of s o i l  Silt (%)  Clay (%)  types  Bulk Density (g/cm )  Field Capacity (%)  3  Sandy Loam  58  31.5  10.5  1.35  25  Silt loam  16  63  21  1.24  49  B u l k d e n s i t y i s a fundamental s o i l p r o p e r t y calculate  soil  engineers  and s o i l  determination density dried  porosity,  a  crucial  scientists.  of bulk  density  that i s used t o  variable The  for irrigation  accuracy  required  i s a b o u t 5% a b s o l u t e .  i s t h e mass p e r u n i t b u l k  t o a constant  (Table  volume o f s o i l  w e i g h t a t 105°C.  Particle  mass p e r u n i t v o l u m e o f s o i l p a r t i c l e s .  bulk  t h a t has been density  i s the  Both o f t h e s e terms a r e  usually  expressed  particle  d e n s i t y a r e known, t h e t o t a l p o r o s i t y c a n be c a l c u l a t e d  using  these  structure) distribution  i n grams/cm .  Soil  in  3  values. control i n soil.  Soil the  total Water  I f both  physical pore movement  bulk  density  properties space  and  i n soil  and  (texture, pore  size  occurs  under  s a t u r a t e d and d e n s i t y and and in  u n s a t u r a t e d c o n d i t i o n s though s o i l  pore  space  also  a f f e c t water  r o o t p e n e t r a t i o n and development. calculating  conditions tillage  soil  moisture  sandy loam and  silt  i r r i g a t i o n systems, Field percentage  loam s o i l s ,  before  water  a  necessary  a profile.  run,  for  under b o t h s u r f a c e and  soil  (30, 35,  i s normally  remaining  in  the  The  i f conventional  each  and a t a l l t e m p e r a t u r e s  C a p a c i t y of of  Such d a t a a r e  s t u d i e s w e r e as  performed  Bulk  aeration status,  movement w i t h i n  s i m u l a t e d i n these  o p e r a t i o n s were  and  pores.  both  trickle  40 °C) .  c o n s i d e r e d as  soil  after  the  a l l  the  g r a v i t a t i o n a l w a t e r has b e e n d r a i n e d ( f r o m c o m p l e t e l y s a t u r a t e d condition) may  be  under  the  free drainage  e x p r e s s e d i n terms of weight  condition.  The  percentage  o r volume.  F o r most  soils  t h i s i s the b e s t moisture c o n d i t i o n f o r p l a n t growth because the soil Field  holds  maximum amount  at f i e l d  research study, f i e l d filling  silt  available  c a p a c i t y a l s o d e p e n d s on s o i l  h o l d more w a t e r  by  of  one  escape).  noted  and  c a p a c i t y than sandy s o i l s .  p o t w i t h sandy loam and  P l a c e d them i n two  A f t e r the f u l l the pots  e v a p o r a t i o n from  plant.  buckets  soils  For  this  determined  the other w i t h  filled  with  water  ( f o r the s o i l a i r  s a t u r a t i o n i s achieved, the time  were c o v e r e d  the s o i l s .  taken to determine  the  texture i n that clay  a n d s a t u r a t e d them f r o m t h e b o t t o m t o t h e t o p to  to  c a p a c i t i e s f o r b o t h s o i l s were  plastic  loam s o i l .  water  with plastic  sheets  Three samples from each  t h e i r moisture content  (MC)  to soil  was  avoid were  gravimetrically  a f t e r 48, 72 and 96 h o u r s o f f r e e d r a i n a g e a f t e r s a t u r a t i o n . the  c a s e o f s a n d y loam s o i l ,  t h e MC  changed i n t h e r a n g e o f 1 t o  3 percentage points  f r o m t h e MC  hours of s a t u r a t i o n  (26 a n d 23 % ) .  was  25%.  In case of s i l t  significantly saturation. was  different  For the s i l t  of the samples  loam s o i l , from  72  loam s o i l ,  In  The  FC  of sandy  t h e changes  hours  till  taken a f t e r loam  48  soil  i n MC w e r e n o t hours  after  i n s i g n i f i c a n t changes  i n MC  o b s e r v e d f r o m 4 9 % a n d t h u s i t (49%) was  120  c o n s i d e r e d as i t s  FC. F i g u r e 3.2 irrigation  show t h e e x p e r i m e n t a l s e t up f o r b o t h s o i l s  systems.  and  100 cm  H  EXPERIMENT BOX Figure  3.2  Experimental  setup.  3.2  P r e - i r r i g a t i o n S o i l Moisture Content A f t e r l e v e l i n g and f l o o d i r r i g a t i o n ,  untouched  till  b o t h s o i l s were  the desired p r e - i r r i g a t i o n  c o n t e n t s were r e a c h e d .  volumetric  left  moisture  The v o l u m e t r i c m o i s t u r e c o n t e n t r e a d i n g s  w e r e t a k e n p e r i o d i c a l l y w i t h TDR p r o b e s i n s e r t e d a t t h e c e n t e r of  each box. For  t h e s a n d y loam s o i l , p r e - i r r i g a t i o n v o l u m e t r i c m o i s t u r e  content  was  19%,  (approximately  and  75%  for silt  of  field  loam  soil,  i t was  capacities).  This  37% initial  v o l u m e t r i c m o i s t u r e c o n t e n t was b a s e d o n t h e Management A l l o w e d Depletion  (MAD) l e v e l o f s o i l w a t e r f o r o n i o n c r o p w h i c h i s 2 5 %  of  capacity  field  amount  (ASCE,  of available  1990).  water  removed  crop's a c t i v e r o o t i n g depth. required  to r e f i l l  crop  uses  precipitation  water  from  deficit  the s o i l  zone  to bring  capacity.  i s the  within  the  or irrigation)  the current  soil  S o i l water d e c r e a s e s as  (évapotranspiration)  (rainfall  s o i l water d e f i c i t ,  water  L i k e w i s e i t i s t h e amount o f w a t e r  the root  moisture conditions to f i e l d the  Soil  and  increases  i s added.  as  Expressed i n  évapotranspiration i n c r e a s e s t h e d e f i c i t a n d  p r e c i p i t a t i o n decreases i t . Allowable s o i l  water d e p l e t i o n l i m i t s  specify  t h e maximum  amount o f s o i l w a t e r t h e i r r i g a t i o n manager c h o o s e s t o a l l o w t h e crop  to  extract  irrigations. used  by  from  the  active  rooting  zone  Only a p o r t i o n of the a v a i l a b l e water  the plant  before  crop  water  stress  between i s easily  develops.  This  depletion  limit  crop growth  differs  stages.  stress during  among c r o p s a n d s h o u l d  That  reduces  c r i t i c a l growth p e r i o d s  and t h e l e a c h i n g p o t e n t i a l i s a high p r o b a b i l i t y  rainfall. Historically,  soil  water  available  optimize  i r r i g a t i o n s have been p l a n n e d t o p r e v e n t t h e  deficit water  research  states  from  exceeding  capacity that  i n the  the depletion  the f i e l d ' s production  growth,  soil  Allowable  water capacity,  50  percent  rooting  3.3  of  zone.  limit  the But  c a n be  and i r r i g a t i o n  total recent  varied  d e p e n d i n g on t h e c r o p , system's  to  stage of capacity.  d e p l e t i o n i s u s u a l l y e x p r e s s e d as a p e r c e n t a g e o f t h e  t o t a l a v a i l a b l e water capacity i n the r o o t i n g  zone,.  I r r i g a t i o n Systems  3.3.1  Surface For  supply  Irrigation  surface  line  irrigation  minute  water  i n the laboratory  tube) a t t h e c e n t e r per  with  the p r o b a b i l i t y of moisture  when m i l d s t r e s s c a n be t o l e r a t e d o r t h e r e of  be v a r i e d  applied  from  through a p l a s t i c  o f t h e box.  (7.74 g a l l o n s  was  a  hose  The f l o w r a t e was 29.3  per minute), which  water (siphon liters  was m e a s u r e d a t  d i f f e r e n t t i m e s o f t h e d a y a n d n i g h t a n d f o u n d t o be a l m o s t t h e same a t a l l t i m e s . the  c a s e o f sandy loam s o i l  loam s o i l . for  The t o t a l  v o l u m e a p p l i e d was 5 g a l l o n s i n  a n d 10 g a l l o n s  i n the case of s i l t  The a p p l i c a t i o n t i m e was 39 s e c o n d s  sandy and s i l t  loam s o i l s r e s p e c t i v e l y .  a n d 77  seconds  3.3.2  Trickle  Irrigation  Pressure gallons  Compensating E m i t t e r s  p e r hour)  for silt  loam  o f 7.6  soil  liters  per hour  a n d 19 LPH  (5 GPH)  s a n d y l o a m s o i l were u s e d f r o m t h e same t a p f o r d r i p The  emitters  centimeter placed a  were  inserted  l o n g and 1 c e n t i m e t e r  a t the center  pressure  during  into  as  tubes  wide p i e c e s  of the boxes.  regulator  a l l runs  plastic  a n d was  kept  recommended  by  the  tied  to  100  iron,  and  was r e g u l a t e d  a t about  83  for  irrigation.  of angled  Pressure  (2  kPa  with  (12 p s i )  manufacturer.  The  e m i t t e r s w e r e c a l i b r a t e d a n d t h e r e s u l t s showed t h a t t h e a c t u a l discharge the  o f t h e 7.6 LPH  19 LPH  (5 GPH)  (2 GPH)  one was  one was a c c u r a t e .  6.8  1 h o u r f o r t h e 19 LPH  for  t h e 6.8  LPH  and  38 liters  (2 GPH)  Application  rate  t h e r e f o r e important  i s one of a  a n d 5 h o u r s 33 m i n u t e s  to apply  19 l i t e r s  (5 g a l l o n s )  of  the c r i t i c a l  aspects  m i c r o - i r r i g a t i o n system.  i n the I t was  to i n v e s t i g a t e the e f f e c t s of a p p l i c a t i o n r a t e  on h o r i z o n t a l and v e r t i c a l  constant  (5 GPH)  rates of the emitters  Calibration  a n d management  Prerequisite  and  (10 g a l l o n s ) r e s p e c t i v e l y .  3.3.2.1 Emitters  design  emitter  (1.8 GPH)  A p p l i c a t i o n time f o r each  r u n was b a s e d on t h e c a l i b r a t e d d i s c h a r g e w h i c h was  LPH  d i s t r i b u t i o n s from a p o i n t  source.  f o r t h e i n v e s t i g a t i o n was a n a c c u r a t e l y c a l i b r a t e d  flow point  The m a t e r i a l  source.  used during  calibration  was  a stop  watch,  a  g r a d u a t e d c y l i n d e r , a n d two b e a k e r s . D u r i n g e a c h s e t t i n g , t h e w a t e r was c o l l e c t e d i n a b e a k e r f o r f i v e minutes and then measured u s i n g a g r a d u a t e d c y l i n d e r .  The  a v e r a g e volume and t i m e o f 10 r e p l i c a t e s was u s e d t o d e t e r m i n e t h e actual  flow  rate  calibrations  of the emitter  were p e r f o r m e d  a p p l i c a t i o n of i r r i g a t i o n  3.4  Temperature Artificial  temperatures  a t 83  kPa  (12 p s i ) .  i n order t o determine  Control heat  lamps  f o r about  were  6 hours.  and monitored  locations  a t the s o i l  w i t h g l a s s mercury 15,  2 0 a n d >20  after irrigation  the time of  water.  used  to  The h e a t  generate from  c o n t r o l l e d w i t h dimmers a t t a c h e d t o t h e l a m p s . measured  Five  with  4  surface.  filling  thermometers Soil  f o r each run.  t h e lamps  was  Temperature  was  at  4  different  t e m p e r a t u r e was m e a s u r e d  thermometers  c e n t i m e t e r s from  desired  a t depths  the s o i l  0-2, 5, 10,  surface  b e f o r e and  The t e m p e r a t u r e o f t h e w a t e r was  v e r y c l o s e t o t h e room t e m p e r a t u r e a t t h e t i m e o f i r r i g a t i o n .  3.5  Evaporation Under  water  both  evaporated  irrigation from  s t a n d i n g on t h e s o i l  sandy  systems, loam  t h e volume  and s i l t  lost  through  irrigation  soils  while  s u r f a c e was d e t e r m i n e d b y t h e P a n m e t h o d .  T h i s method measures t h e e v a p o r a t i o n r a t e water  loam  of  e v a p o r a t i o n from  from t h e volume o f  a given surface  area of  w a t e r and  t h e t i m e w a t e r was  s t a n d i n g i n the  T h r e e p a n s e a c h c o n t a i n i n g 5 00 mL soil  s u r f a c e a t 30,  was  standing  and  (ponded)  at  the  simulate  the  evaporation  to  irrigation  water.  placed  on  the  application  of water were p l a c e d  35,  irrigation  In  soil  time  the  40 °C f o r t h e t i m e  the  soil  case  surface  plus  pan.  of  time  surface losses  drip  for  a  irrigation  was  standing pans  equal  ponded  water  surface  from  irrigation  duration  water  under  on  on  were  to the  the soil  surface. The  rate  of  evaporation,  c a l c u l a t e d using Equation  E  where V i and V pan  (mL),  A  P  2  R  =  E  (mm/hr) f r o m  R  v,-v  1 A  f 2  are the i n i t i a l  time  soil V  w  and  600  was  (3.1)  (600)  :  T  and  final  volume of w a t e r i n the  i s t h e s u r f a c e a r e a o f w a t e r i n t h e pan  (min),  pans  3.1.  t h e r e c e s s i o n t i m e o r t h e t i m e w a t e r was surface  these  i s the c o n v e r s i o n  (cm ) , T 2  standing over  the  R  is soil  factor to convert  the  K n o w i n g t h e s u r f a c e a r e a o f i r r i g a t i o n w a t e r p o n d e d on  the  f r o m m i n u t e s t o h o u r a n d mL  s u r f a c e , the  (L) was  total  to  mm.  volume of i r r i g a t i o n  estimated using Equation  3.2.  water  evaporated,  v.-v  V  where A over  soil  i s the surface area  P W  surface  (cm ), 2  (3.2)  2  1000  of i r r i g a t i o n water  and 1000 t h e c o n v e r s i o n  a v e r a g e o f t h e volume o f w a t e r e v a p o r a t e d was  used  f o r calculating  t h e volume  e v a p o r a t e d w h i l e s t a n d i n g on t h e s o i l  3.6  S o i l Water Measurement  goal  A l l types  oriented.  of research  Therefore,  a p p r o p r i a t e sampling  The  sampling  horizontal of  intervals  application  surface.  25  surface.  l a y o u t i s shown i n F i g u r e  a c t i v i t y a r e supposed t o be t o t h i n k about an  around t h e p o i n t o f a p p l i c a t i o n f o r F o r t h i s purpose, a sampling  layout  for soil  o f 25 c e n t i m e t e r s ,  A 15 c e n t i m e t e r  shown i n f i g u r e 3 . 3  water  layout  r a d i a l l y as w e l l as v e r t i c a l l y .  and moving  centimeters  irrigation  The p l a n was t o h a v e d a t a p o i n t s move away  c h o s e n up t o 60 c e n t i m e t e r were  of  pans  l a y o u t t h a t p r o v i d e s us d a t a i n a p a t t e r n t o  both i r r i g a t i o n techniques.  from t h e p o i n t source  The  from t h e t h r e e  i t was i m p e r a t i v e  e x p l a i n the water d i s t r i b u t i o n  p l a n was d e v e l o p e d .  factor.  Strategy  The s o i l w a t e r m o n i t o r i n g / r e a d i n g 3 . 3 (a & b) .  standing  outward interval depth.  radially (a&b).  water  measurement  was  starting  from t h e p o i n t  t o t h e edge  of the wetted  f o r v e r t i c a l measurement Thus, t h e r e a d i n g  a n d 15 c e n t i m e t e r s  was  intervals  vertically  as  The  readings f o r water  c o n t e n t w e r e t a k e n u s i n g TDR  Soil  M o i s t u r e M e a s u r e m e n t I n s t r u m e n t , M o i s t u r e Point™ M o d e l MP-719, and  Moisture  horizontally  Point from  Probe the  Type-K  center  at  and  at  an  increment  of  25  cm  an  increment  of  15  cm  v e r t i c a l l y from the water source i n o r d e r t o determine the water content  distribution  patterns  in  the  soil  profile  under  investigation. The a v e r a g e v a l u e o f t h r e e r e a d i n g s f o r e a c h d e p t h a t p o i n t was  used.  The  probe had  four  15 cm  l o n g segments  each which  measured d i r e c t l y the average v o l u m e t r i c m o i s t u r e c o n t e n t i n the soil  layer.  F i g 3.3(a).  Volumetric Soil Moisture Reading for both s o i l s for Surface and irrigation Systems. Irrigation Source  F i g 3.3(b).  Top View of Reading Points for Surface and M i c r o - i r r i g a t i o n Systems.  Depths Micro-  3.7  S o i l Water D i s t r i b u t i o n  3.7.1  Soil The  Water Distribution  by Volume  Volume b a l a n c e a p p r o a c h was a d o p t e d  water d i s t r i b u t i o n i n a l l four layers on  Balance  the p r e - i r r i g a t i o n  (D  D  1(  and p o s t - i r r i g a t i o n  t o study the s o i l D , and D ) .  2/  3  Based  4  volumetric moisture  c o n t e n t d a t a , t h e change i n v o l u m e t r i c w a t e r c o n t e n t a s a r e s u l t of  added w a t e r was d e t e r m i n e d a n d p l o t t e d .  was  The f o l l o w i n g  relation  u s e d f o r t h e c a l c u l a t i o n o f w a t e r volume w i t h i n each V  w  = V  s  A0  depth: (3.3)  V  Where, V  w  =  volume o f w a t e r added t o t h e l a y e r  V  s  =  volume t o t h e s o i l  =  change i n v o l u m e t r i c w a t e r c o n t e n t  A0  V  layer  (liters)  (liters)  The w a t e r v o l u m e s c a l c u l a t e d w i t h t h i s a p p r o a c h  for a l l the  d e p t h s w i t h i n t h e r o o t z o n e were u s e d t o d e t e r m i n e what p e r c e n t a g e of  t h e t o t a l amount o f w a t e r a p p l i e d was s t o r e d i n e a c h  3.7.2  A Physical An  for  Understanding  understanding of s o i l  both  soils,  temperatures  under both  of Wetted water  Kriging option  Profile  d i s t r i b u t i o n was d e v e l o p e d  irrigation  (30°, 35°, a n d 40 °C) .  depth.  techniques a t a l l three  Contours  were drawn u s i n g  ( G r i d d i n g Method) o f t h e G r a p h i c S o f t w a r e SURFER  ( V e r s i o n 7, 1999) f o r b o t h s o i l s a n d i r r i g a t i o n methods, a n d f o r all  f o u r depths u s i n g t h e v o l u m e t r i c m o i s t u r e content r e a d i n g s a t  different  points  and temperatures.  I n these contours,  wetted  p a t t e r n s were s t u d i e d a n d t h e d i f f e r e n c e s w i t h i n e a c h s o i l irrigation  method  and depths  at different  type,  temperatures  were  i d e n t i f i e d and d i s c u s s e d .  3.7.3  Wetting Front Movement  The w e t t i n g f r o n t was d e f i n e d as t h e l o c a t i o n where t h e s o i l moisture content decreased 2% m o i s t u r e 1982) .  from g r e a t e r s o i l m o i s t u r e c o n t e n t t o  of the i n i t i a l  soil  moisture  content  (Mostaghimi,  I n t h e c o n t o u r s , t h e w e t t i n g f r o n t s were i d e n t i f i e d b y t h e  contour w i t h t i n y v e r t i c a l  lines  techniques i n a l l f o u r depths  f o r both s o i l s  and i r r i g a t i o n  a t 30, 35, a n d 40 °C t e m p e r a t u r e s .  The s a t u r a t e d w a t e r e n t r y zone was a l s o o b s e r v e d t h r o u g h o u t t h e irrigation period.  3.8  S o i l Water Measurement Technique The t i m e d o m a i n r e f l e c t o m e t r y t e c h n i q u e was p r e f e r r e d o v e r  other  soil  following  moisture  content  measuring  techniques  f o r the  reasons:  1.  I t i s a c c u r a t e , p o r t a b l e , and v e r y simple t o operate.  2.  I t i s quick  and measures  directly at different soil 3.  No  soil  removed  sampling from  volumetric  content  depths.  i s required,  experimental  moisture  that  plot/field  i s why  no  soil  a n d minimum  i s soil  disturbance occurs while determining s o i l moisture content. 4.  Measurements  of v o l u m e t r i c water  content  appear  t o be  substantially  independent  of s o i l  type  and s a l i n i t y f o r  many common s o i l s (Topp e t a l . , 1 9 8 0 ) . 3.8.1  TDR Soil  Moisture  Point  Probe  Calibration  C a l i b r a t i o n was p e r f o r m e d f o r b o t h s o i l s i n v e s t i g a t e d i n t h e study. to  The r e a s o n f o r i n d i v i d u a l c a l i b r a t i o n was t h a t a c c o r d i n g et a l . (1992),  Roth  calibration.  Levitt  demands o n a c c u r a c y r e q u i r e  (1989)  individual  also states that a careful  o f Topp's p o l y n o m i a l c u r v e f o r v a r i o u s s o i l t y p e s e x h i b i t different  values of d i e l e c t r i c constant i n response  content.  analysis slightly t o water  Thus, i t was t h o u g h t t h a t s o i l s p e c i f i c c a l i b r a t i o n f o r  individual  probes  i s compulsory  f o r more a c c u r a t e s o i l  water  determination. Calibration probes  was p e r f o r m e d  t o be u s e d  accomplished Moisture  by  Content  f o r data  comparing  collection.  t h e TDR  a n d Time D e l a y )  V o l u m e t r i c Water Content.  The c a l i b r a t i o n  readings  TDR r e a d i n g s a t f o u r d e p t h s  was  (both V o l u m e t r i c  t o those of the Gravimetric  For t h i s purpose, three s o i l  from each d e p t h were c o l l e c t e d the  f o r t h e s o i l s i n t h e boxes f o r  samples  from t h e box i m m e d i a t e l y (0-15  cm, 1 5 - 3 0 cm, 3 0 - 4 5  after cm,  a n d 4 5 - 6 0 cm) f o r 38 d a y s a f t e r w e t t i n g o f s o i l . A l o n g w i t h t a k i n g t h e TDR r e a d i n g s (MC a n d Time D e l a y ) , t h e v o l u m e t r i c w a t e r c o n t e n t was m e a s u r e d b y w e i g h i n g w e t a n d o v e n dried  samples  (gravimetric)  f o r each  soil  depth.  versus Volumetric water  Volumetric water content  content  (TDR) a n d Time  D e l a y d a t a were used t o f i t an a p p r o p r i a t e r e g r e s s i o n e q u a t i o n .  CHAPTER IV RESULTS AND DISCUSSION This  chapter  distribution  i n  discusses sandy  and  the  results  silt  loam  of  soils  soil  water  at  various  temperatures under s u r f a c e and t r i c k l e i r r i g a t i o n systems. study  also  distribution  delineates affected  the significance by  different  of  the s o i l  temperatures;  The water  physical  u n d e r s t a n d i n g o f w e t t e d p r o f i l e s , w e t t i n g f r o n t movement, v o l u m e balance  of  t h e water  applied  by  two d i f f e r e n t  methods; a n d an i n s i g h t i n t o s o i l w a t e r  4.1  profiles.  TDR C a l i b r a t i o n  The  average v o l u m e t r i c water  c o n t e n t s measured  and o b t a i n e d g r a v i m e t r i c a l l y from a c t u a l s o i l the  irrigation  TDR Time D e l a y r e a d i n g s f o r s i l t  loam  w i t h TDR,  samples a l o n g w i t h and sandy  loam a r e  the relationships  between  g i v e n i n T a b l e s 4.1 a n d 4.2 r e s p e c t i v e l y . Figures  4.1  gravimetrically  and  4.2  show  determined volumetric  water  c o n t e n t s a n d TDR  m e a s u r e m e n t s ; t h e g r a v i m e t r i c w a t e r c o n t e n t V s TDR Time D e l a y ; a n d TDR w a t e r c o n t e n t V s Time D e l a y m e a s u r e m e n t s f o r s a n d y and s i l t  loam s o i l s .  loam  The  calculated  determination  regression  (r ) are also 2  equations  included  and  coefficients  i n the plots  of  and a r e as  below: for  sandy  loam  soil,  0^=1.92410^-18.658  r =0.89  (4.1)  0 ^ =31.308x -63.523  r =0.86  (4.2)  e  r = 0.99  (4.3)  2  2  TDR  T O R  and  = 16.379T -23.615 TOR  for silt  loam  2  soil,  0^=1.20060^-1.8981  r =0.85  0 ^ =23.02x -39.125  r =0.85  T D R  = 19. 1 0 3 t  .  2  TDR  0  (4.4)  2  -30.755 r = 0.99  (4.6)  2  tdr  T h e s e d a t a show s a t i s f a c t o r y c l o s e and  gravimetrically  i n bulk  horizontal  factor  gra  v and 0  T D R  and  vertical  planes  In addition  (experimental  error).  containing  the  The  may b e due t o  d e n s i t y measurement, s p a t i a l v a r i a b i l i t y  measuring volumes. a  c o r r e l a t i o n b e t w e e n TDR  d e t e r m i n e d water c o n t e n t measurements.  lower c o r r e l a t i o n c o e f f i c i e n t between 0 error  (4.5)  i n the  sampling  t o t h i s , human e r r o r  can a l s o  and be  Table  4.1  Days After Wetting 0 2 3 4 5 6 7 8 9 10 12  Average Moisture for sandy loam. Gravimetric V o l . M.C. (%) (M. C. %*Bulk Density) 36.90 25.91 24.69 22 .42 22 . 04 22 . 56 21.31 20.87 19.61 19 .79 18.17  Content  and Time  Delay  M o i s t u r e P o i n t Probe Readings MC  Time Delay  (nano-sec) 28 .44 21.61 23 .41 21.31 22.08 20.55 20.90 19 .45 20.63 20.87 19.57  3 .19 2 .73 2 . 84 2 .74 2 . 79 2 .70 2 . 72 2 . 64 2.69 2 .74 2.66  Grav. MC and Time Delay 40 -,  is  r  2.6  1 1  11111111111  2.7  2.8  i  i  i  2.9  3  3.1  Time Delay (nano-sec)  TDR MC and Time Delay  3.2  Table  4.2  Average Moisture for S i l t Loam.  Days After Wetting  Gravimetric V o l . M.C. (%) (M. C.%*Bulk Density)  1 2 3 5 6 8 9 10 15 16 17 18 19 23 25 26 28 32 38  51.82 50.78 48.96 45.88 48 .23 45.83 47.98 47.90 46.19 43 .13 43 .32 40.91 39.85 39 .48 39 . 68 34.80 35.51 34.40 34.55  Content  and Time  Delay  Moisture P o i n t Probe Readings M.C. (%) 41.45 41.62 44.58 40.45 40.50 41. 52 43 .23 42 . 03 37.90 37.61 36.45 34.98 32.56 33 .87 34.40 34 .49 33.18 30.53 31.00  Time Delay (nano-sec) 3 .80 3 .82 3 .94 3 .73 3 .71 3 .78 3 .87 3 .79 3 .59 3 .56 3 .52 3 .45 3 .32 3.38 3.39 3 .43 3.36 3 .21 3 .23  Overall average Grav. MC & Time Delay  3.1  3.2  3.3  3.4  3.5  3.6  3.7  3.8  3.9  4.0  Time Delay (nano-sec)  Overall Avg. Moisture Point MC & Time Delay 50.00 -  u  45.00  •g 40.00  I » 35.00  y = 19.103x - 30.755  •1 30.00  IT = 0.996  25.00 3.1  3.2  3.3  3.4  3.5  3.6  3.7  3.9  Time Delay (nano-sec)  Figure  4.2 Comparision silt loam  between soil.  TDR and gravimetric  data for  4.2  S o i l Temperatures  Both  the  soils  showed  distinguishable  t e m p e r a t u r e b e f o r e and a f t e r t h e a p p l i c a t i o n at  different  o p e r a t i n g temperature.  summarize t h e s e changes i n sandy  for  three different two i r r i g a t i o n  change  sandy  loam  in soil soil  t h e r e was to  or  °C  b e f o r e and  than  at  lower  silt  soil  temperature.  surface irrigation.  4.4).  loam.  loam and  and soils  40  °C)  the  Under  cm  After  However,  at lower  soil  temperature  t e m p e r a t u r e b e f o r e and a f t e r t h e a p p l i c a t i o n  w a t e r were n o t s i g n i f i c a n t l y  different.  of  prior  a t 40  remained  of the water h o l d i n g the  cm  for silt  especially  temperatures  15  irrigation  temperature along the s o i l  irrigation  (40 °C)  Beyond  same  in  depth.  temperature  the  rate  irrigation  t o 15  d i f f e r e n t b e f o r e and a f t e r i r r i g a t i o n ,  (Figure  water  4.5,  temperature a t h i g h e r temperature  c o n s t a n t up t o 5 cm d e p t h , b e c a u s e of  after  s i m i l a r p a t t e r n up  method t h e changes i n s o i l loam was  silt  (30, 35,  n o t any s i g n i f i c a n t c h a n g e i n s o i l  after  4.4,  as shown i n F i g u r e 4.3,  temperature  exhibited  more p r o n o u n c e d  soil  methods.  A l s o t h e change i n s o i l is  and  o p e r a t i n g temperatures  Under s u r f a c e i r r i g a t i o n , of  loam  in  of i r r i g a t i o n  T a b l e s 4.3,  4.6  under  changes  capacity  changes  in  irrigation  T a b l e 4.3 S a n d y Loam S o i l T e m p e r a t u r e s a t D i f f e r e n t D e p t h s , B e f o r e a n d After Surface I r r i g a t i o n Soil Depth (cam) 0-2 5 10 15 20 >20  S o i l Temperatures Ti = 30 °C After Before Irrigation Irrigation 29. 0 28.4 27.0 24.7 24.0 24.0  28.0 27.6 27 . 0 25.8 24.0 24.0  T = 35 °C After Before Irrigation Irrigation 2  33 .0 30.0 28.0 25.0 24.4 24.4  29.0 28.8 27.0 25.0 24.4 24.4  T = 40 °C After Before Irrigation Irrigation 3  38.0 35.0 28.0 24.5 24.0 24.0  35.0 32.0 30.0 25.0 24.2 24.2  39  ^ 38 _2 37 f  36 "o 35 34 33 32 31 30 1 29 2 28 <u 27 c a 26 25 24 'o 23 22  -\  -\ -\ -\ - :  Before Surface irrigation  -|  -i _ E  -\ - |  ITe:  egre  "(ZI  — T l = 30 Degree Celsius - T2 = 35 Degree Celsius - - - T3 = 40 Degree Celsius  - j  - Ê - ï  0-2  0-2  F i g u r e 4.3  5  10  15  20  >20  10 Soil Depths (cm)  15  20  >20  S a n d y Loam S o i l T e m p e r a t u r e s a t D i f f e r e n t Before andA f t e r Surface I r r i g a t i o n .  Depths  T a b l e 4.4 S i l t Loam S o i l T e m p e r a t u r e s a t D i f f e r e n t D e p t h s , B e f o r e a n d After Surface I r r i g a t i o n Soil Depth (cm) 0-2 5 10 15 20 >20  S o i l Temperatures Ti = 30 °C After Before Irrigation Irrigation 28.6 27.8 25.0 25.0 24.2 24.2  30.0 29.0 26.6 26.0 25.6 25.0  T = 35 °C After Before Irrigation Irrigation 2  34.0 29.0 25.6 25.0 24.6 24.2  35.0 33 .0 30.0 26.0 25.0 25.0  = 40 °C After Before Irrigation Irrigation T  40.0 33.0 29.0 25.0 24.8 24.4  3  40.0 40.0 36.0 31.0 26.2 25.6  ^42  •I  "«5  T l = 30 Degree Celsius T2 = 35 Degree Celsius T3 = 40 Degree Celsius  40  « 38 S 32 34 -• g 30  Before Surface Irrigation.  &28 u H 26 22 10  0-2  15  20  >20  42 40  After Surface Irrigation  38 36 00  u  34  T3  32  |  30  -E  & 28 |  26  •S 24 22  0-2  F i g u r e 4.4  5  10 Soil Depth (cm)  15  20  S i l t Loam S o i l T e m p e r a t u r e s a t D i f f e r e n t Before and A f t e r Surface I r r i g a t i o n .  >20  Depths  Unlike  sandy  loam,  constant below  the s o i l  irrigation,  temperatures  and  40  °C)  temperature along the s o i l  in  soil  a  with  little  pronounced  sandy loam s o i l  temperature  profile  However,  (Figure  p a t t e r n b e f o r e and a f t e r i r r i g a t i o n surface almost  irrigation, unchanged  Nonetheless,  d i d not  after  accumulation application  both  contrary  temperature depth  the s o i l  to  under  trickle  s i g n i f i c a n t changes i n s o i l trickle  irrigation  application  region  irrigation.  a  15  40  °C,  up  to  soil 5  cm  due  to  water  of  slow  water  result  temperature p r o f i l e  remained  irrigation.  changes  Silt  with  similar  cm  at  probably as  after  Likewise with  trickle  significant  and  showed  ( F i g u r e 4.5).  irrigation,  this  3 5 °C)  after  soil  4.4).  to  temperature below and  in  temperature  surface irrigation,  show a n y  trickle within  before  after  showed s i g n i f i c a n t  prior  (3 0 a n d  was  at higher  changes  i r r i g a t i o n a t 40 °C, however t h e changes i n s o i l depth at lower temperatures  soil  (30 a n d 3 5  different  d e p t h up t o 15 cm  With t r i c k l e i r r i g a t i o n ,  soil  loam  of i r r i g a t i o n water.  t h e p a t t e r n was  (35  difference  in silt  10 cm a t l o w e r o p e r a t i n g t e m p e r a t u r e  °C) b e f o r e t h e a p p l i c a t i o n the  temperature  loam  soil  b e f o r e and  at a l l operating temperatures.  showed after  P r i o r to the  o f i r r i g a t i o n w a t e r , a t 40 °C, changes i n t e m p e r a t u r e  w e r e o b s e r v e d e v e n up t o 20 cm d e p t h , where as s u c h c h a n g e s w e r e o n l y pronounced  up t o 10 cm d e p t h a t 30 a n d 35 °C  ( F i g u r e 4.6) .  T a b l e 4.5 S a n d y Loam S o i l T e m p e r a t u r e s a t D i f f e r e n t After Trickle Irrigation Soil Depth (can) 0-2 5 10 15 20 >20  Depths, Before and  S o i l Temperatures Ti = 30 °C Before Irrigation 28.8 28.6 27.0 25.4 24.6 24.0  After Irrigation 28.4 28.0 26.2 26.0 24.9 24.4  T = 35 °C After Before Irrigation Irrigation 2  33 .2 29.0 26.8 25.0 24.8 24.4  34.0 28.2 27 . 0 26.2 25.0 25.0  T = 40 °C After Before Irrigation Irrigation 3  40.0 35.2 28.4 24.8 24.2 24.0  40.0 39.0 33.0 28.4 27 .2 27.0  ^ J  42 t 40 -È  — T l = 30 Degree Celsius - T2 = 35 Degree Celsius - - - T3 = 40 Degree Celsius  «o 38 S- 34 \  Before Trickle Irrigation  ë 32 30  g 28 26 o 24  00  i  22 0-2  10  0-2  F i g u r e 4.5  5  10 Soil Depth (cm)  15  20  >20  15  20  >20  S a n d y Loam S o i l T e m p e r a t u r e s a t D i f f e r e n t Before and A f t e r T r i c k l e I r r i g a t i o n .  Depths  T a b l e 4.6 S i l t Loam S o i l T e m p e r a t u r e s a t D i f f e r e n t After Trickle Irrigation Soil Depth (cm) 0-2 5 10 15 20 >20  Depths, Before and  S o i l Temperatures Ti = 30 °C After Before Irrigation Irrigation 29.2  27 . 0 25.0 25.0 24.6 24.4  30.0 29.0 28.0 26.2 25.6 25.2  T = 35 °C 2  Before Irrigation 34.0 29.0 25.6 25.0 24.6 24.2  After Irrigation 35.0 34.0 34.0 30.2 27.9 27.4  = 40 °C After Before Irrigation Irrigation T  40.0 36.0 30.2 28.0 25.8 25.4  3  40.0 40.0 38.0 34.2 33.7 32.0  ^ 44 .3 42 -f en 1w 40 38 -f 36 •a 34 32 30 a. 28 -I 3 <u H  1  • T l = 30 Degree Celsius T2 = 35 Degree Celsius •T3 =40 Degree Celsius Before Trickle Irrigation  26-f 22  24  0-2  10  15  46 44 42 40 u 38 u 36 I I 34 & 8 32 o  20  >20  After Trickle Irrigation  30 28 26 24 22 0-2  F i g u r e 4.6  5  10 Soil Depth (cm)  15  20  S i l t Loam S o i l T e m p e r a t u r e s a t D i f f e r e n t Before and A f t e r T r i c k l e I r r i g a t i o n .  >20  Depths  The  differences i n soil  loam and t h e s i l t different  t e m p e r a t u r e p r o f i l e s showed b y t h e s a n d y  loan s o i l s p r i o r  t o , and a f t e r  irrigation at  t e m p e r a t u r e s must h a v e c a u s e d b y t h e d i f f e r e n c e s i n  the c o n d u c t i o n of heat of the s o i l s . As occurs  t h e F o u r i e r ' s Law s t a t e s t h a t h e a t f l o w t h r o u g h a medium i n response t o a temperature gradient,  high concentration  to regions  from regions  of low concentration,  o f movement i s d e p e n d e n t on a p r o p e r t y  of  and the r a t e  o f t h e medium c a l l e d i t s  t h e r m a l c o n d u c t i v i t y , k.  G=  Where  k  s  denotes  - f ,- VIl k s  dz  k s  2  the thermal  temperature and z i s v e r t i c a l the  equation  conductivity distance.  i s due t o t h e o p p o s i t e  that of the temperature gradient. on  the s o i l s  water  composition,  content.  Mineral  conductivities,  while  intermediate.  soils organic  In general,  causes the s o i l ' s water replaces has  a very  of the s o i l ,  The n e g a t i v e  direction  T is  sign i n  of heat  flow to  Thermal c o n d u c t i v i t y depends  and i n p a r t i c u l a r ,  c o n d u c t i v i t i e s and w e l l - h u m i f i e d as  (4.7)  z — z,  generally soils  have  high  generally  loamy s o i l s  increasing  varies with  thermal  have  low  are characterized  the moisture  thermal c o n d u c t i v i t y to increase,  t h e a i r between t h e s o i l  soil  particles.  content  because the Still air  l o w t h e r m a l c o n d u c t i v i t y , compared t o w a t e r .  Under s u r f a c e i r r i g a t i o n , silt to  loam s o i l the s o i l  t e m p e r a t u r e s b e f o r e a n d a f t e r i r r i g a t i o n w e r e due  c o m p o s i t i o n s and m o i s t u r e  capacities).  The c h a n g e s i n t h e a f t e r  p a t t e r n s ' were water. soil  caused  by  The c h a n g e was more o b v i o u s  due t o t h e l o n g e r p o n d i n g which  changed  the s o i l  profile  ( f i g u r e s 4.3 & 4 . 4 ) .  The  increase  irrigation of  i n the case  when  water  holding  temperature  the  of the applied  the applied  temperature  (water  infiltrated  of s i l t water  temperature,  infiltrated  into  i n the s o i l  infiltration temperature  patterns  changes i n s i l t  (figures  and i t  the  soil  as t h e  were i n c r e a s e d by t h e deeper  after  4.5  gradually  loam s o i l  up  t o 10  retention i n s i l t temperature  loam  changes  cm  were  soil  and a t b o t h  most  probably  O v e r a l l under  observed  and  systems  layers  loam  due  trickle  t o deeper  in silt  40  °C  up t o 2 0  soil  to  water  irrigation depths,  as  soil. soils,  water  a t higher temperatures,  which  changed  the s o i l s  temperatures,  changes  were  g r e a t e r depths  till  35  was  temperature changed v e r y s l o w l y  depth  soil.  irrigation  moved t o t h e d e e p e r  The p a t t e r n  t e m p e r a t u r e s were p r o m i n e n t  compared t o s u r f a c e i r r i g a t i o n both  a n d 4.6) .  irrigation,  A l s o a t 35 °C t h e s o i l  Under  soil  o f a p p l i e d water hence c a u s i n g t h e changes i n t h e  pronounced  cm d e p t h .  profiles  loam  at  same i s t r u e i n t h e c a s e o f t r i c k l e i r r i g a t i o n  temperature  and  content  the temperature  surface  more  t h e d i f f e r e n c e s i n sandy loam and  and i n b o t h  that as  i s why  the  compared  to  temperature the  lower  temperatures. the  The s o i l  differences  t e x t u r e must a l s o h a v e p l a y e d  i n the temperature patterns  due  a role i n  to the water  h o l d i n g c a p a c i t i e s and t h e r m a l c o n d u c t i v i t i e s .  4.3  Evaporation  Losses  Evaporation  losses  under s u r f a c e  from  and t r i c k l e  s u m m a r i z e d i n T a b l e 4.6.  sandy  irrigation  short water ponding duration. under  trickle  and  a t 30°,  The e v a p o r a t i o n  s o i l were n e g l i g i b l e under s u r f a c e  duration  loam  silt 35°,  a n d 40 °C a r e  l o s s e s from sandy loam  i r r i g a t i o n m a i n l y because of  were n e g l i g i b l e  f a s t e r w a t e r i n f i l t r a t i o n i n t o the sandy loam s o i l . in silt  soil  irrigation  under  both  loam s o i l  as compared  systems.  e v e n t h o u g h t h e d u r a t i o n o f w a t e r p o n d i n g was  water  irrigation,  was  much  compared  i n comparison to surface  But i n the case of s u r f a c e ponded  as  under  irrigation,  greater  as  to  to  surface trickle longer  the  of the trickle  t h e r e f o r e more w a t e r e v a p o r a t e d f r o m t h e s i l t  s o i l under s u r f a c e  irrigation  system.  loam  irrigation.  the surface area  compared  to  losses  t o sandy  irrigation,  irrigation  5-fold  The  the  trickle  were  However,  t o o , due  irrigation  under  losses  soils  The l o s s e s c o r r e c t e d f o r t h e same  irrigation  were s i g n i f i c a n t  loam  loam  T a b l e 4.7  E v a p o r a t i o n f r o m S a n d y Loam a n d S i l t Loam S o i l s a t D i f f e r e n t T e m p e r a t u r e s u n d e r and T r i c k l e I r r i g a t i o n Systems. Surface Sandy Loam S o i l  Trickle  Irrigation S i l t Loam S o i l  Sandy Loam S o i l  Surface  Irrigation Silt  Loam S o i l  Temperature (°C)  Evaporat i o n Rate (mm/h)  30  0.46  3  negligible  321  2.44  60  0.48  372  0.52  35  0.77  3  negligible  220  2 . 81  60  0.55  370  0.57  40  0.92  3  negligible  178  2.75  60  0.42  360  0.54  Duration Duration Volume o f Duration Volume o f Duration Volume o f Volume o f o f Water T o t a l A p p l i e d of Water T o t a l A p p l i e d of Water T o t a l A p p l i e d o f Water T o t a l A p p l i e d Ponding Ponding Water Ponding Water Ponding Water Water (min) (min) Evaporated (min) Evaporated (min) Evaporated Evaporated (L) (L) (L) (L)  4.4  S o i l Water D i s t r i b u t i o n  Many r e s e a r c h e r s some  degree  practically  gravitational diffusion  have  flow  and  shown  that  every  physical  capillary  temperature process  movement  and f l o w of gases i n s o i l .  affects  of  such  water,  sandy  loam  irrigation  and  silt  systems.  loam  soils  Both i r r i g a t i o n  s o i l moisture content p r o f i l e s  4.4.1  surface  and  the  within trickle  water volume b a l a n c e  and  are addressed.  Volume Balance  The evaluate stored silt  under  as and  This s e c t i o n discusses  i n f l u e n c e o f t e m p e r a t u r e on i r r i g a t i o n w a t e r d i s t r i b u t i o n  to  irrigation  w a t e r v o l u m e b a l a n c e a p p r o a c h was  the e f f e c t s of  i n different  temperature  on  l a y e r s of the root  the q u a n t i t y zone  i n sandy  loam s o i l s under s u r f a c e and t r i c k l e i r r i g a t i o n  4.4.1.1 Surface Irrigation I n sandy  loam s o i l ,  a p p l i e d w a t e r was  depth  Di  12.60  liters  the t o t a l  (0-15cm)  surface i r r i g a t i o n ,  s t o r e d i n t h e t o p 15  temperatures t e s t e d at  30,  equivalent  of  to  water  loam  and  methods.  System  under  three  used  cm s o i l  (Figure 4.7). 35,  and  to 93.95,  40  °C  The were  88.42,  a p p l i e d water, r e s p e c t i v e l y .  and  most o f  the  l a y e r f o r a l l the volumes 17.85,  66.32  stored i n 16.80,  and  percent of  T a b l e 4.8  P e r c e n t o f T o t a l A p p l i e d W a t e r S t o r e d i n e a c h D e p t h i n S a n d y Loam S o i l a t D i f f e r e n t Temperatures under S u r f a c e I r r i g a t i o n System.  Soil Depth (cm)  Soil Type  Di D D D Di Sandy D Loam D D D D D D 2  3  4  2  3  4  x  2  3  4  (0-15cm) (15-30cm) (30-45cm) (45-60cm) (0-15cm) (15-3Ocm) (30-45cm) (45-60cm) (0-15cm) (15-30cm) (30-45cm) (45-60cm)  Operating Temperatures (°C)  Volumetric Moisture Content (%) [before irrigation]  Volumetric Moisture Content (%) [after Irrigation]  Percent Stored (%)  30 30 30 30 35 35 35 35 40 40 40 40  18.6 21.2 22.9 39.0 19.2 21.3 34.6 40.0 19.1 22 .3 23 .1 34.8  30.5 21.6 23 .1 39.0 30.4 22.1 35.0 40.0 27.5 24.8 24.2 35.1  11.90 0.40 0.20 0.00 11.20 0.80 0.40 0.00 8.40 2.50 1.10 0.30  Volume o f irrigation water stored (L) 17.85 0.60 0.30 0. 00 16.80 1.20 0.60 0.00 12 .60 3 .75 1.65 0.45  Total Percent of applied water i n Total entire Volume root-zone Applied (%) (%) 93.95 3.16 1.58 0.00 88.42 6.32 3.16 0.00 66.32 19.74 8. 68 2.37  98.68  97.89  97.11  100 90 80 u  .1 "Eh  o  70 60  • 30 Degree Celsius (H 35 Degree Celsius H 40 Degree Celsius  i il  50 40  o  30  s ë  20 10 0  i  D l (0-15 cm)  l  D2 (15-30 cm)  rjujglllll j  l  D3 (30-45 cm)  i  1  D4 (45-60 cm)  Soil Depths  Figure  4.7 Percent of Total Applied Water Stored Depths of Sandy Loam Soil at Different under Surface I r r i g a t i o n System.  in Different Temperatures  Table  4.8  summarizes  d i f f e r e n t l a y e r s Di D  4  (45-60  surface  cm)  of  the  layer  At  (Di) .  stored  -  As  where  D  loam  the  3 0 °C,  The  cm),  quantities  soil  at  30,  water D  and  4.7,  about  6 and  2 9 percent  compared t o t h a t  volumes  of  stored  were  f r o m 30  °C,  68  to  f r o m 3 0 t o 40 increase  °C.  f i n a l l y t o 40  The  l o w e r most  liter,  3  i n this  The  °C was  more w a t e r  was  35  and  40  °C,  the  was  2  and  40  °C,  D,  and  3  at  higher  50  percent  84  relative  w a t e r was s t o r e d was  This  was  s t o r e d i n the  that  percent  percentage  any  i n layer  applied  is  layer  35 D. 2  water  of the a p p l i e d water  p r o b a b l y b e c a u s e most o f top  the  in  loam s o i l  Figure  the major p o r t i o n of the  i n v e r s e l y r e l a t e d to the  was  layer.  illustrated  (Di) .  at  approximately  a p p l i e d water stored i n s i l t  irrigation  i n top  receive  percent,  w i t h s a n d y loam s o i l , stored  same as  35 °C) , however a t 40 °C  t o 2.37  volume of t o t a l  Likewise,  d i d not  4  layer.  surface  almost the  (30 and  equivalent  a p p l i e d w a t e r was  under  I n case of l a y e r D ,  layer D  lower temperatures  stored  top  i n s o i l water w i t h i n c r e a s i n g temperature from 3 0 to  and  0.45  f r o m 35  under  i n the  stored  i n layer D  and  the  2  water  in  lower  i n lower l a y e r s - D ,  percentage increase percent  °C  the  at  The  35  40  volume of w a t e r s t o r e d  temperatures. to  stored  (30-45 cm),  3  35,  from F i g u r e  pattern reversed  higher  of  (15-30 cm),  2  evident  higher  i n Di l a y e r as  respectively. 4  sandy  irrigation.  temperature,  D  (0-15  the  Also  the  increase  amount o f  4.8. applied water  i n temperature.  T a b l e 4.9  Volumetric Moisture Content i nS i l t I r r i g a t i o n System.  Soil Depth (cm)  Soil Type  Di D D D D Silt D Loam D D D D D D  2  3  4  1  2  3  4  x  2  3  4  (0-15cm) (15-30cm) ('30-45cm) (45-60cm) (0-15cm) (15-30cm) (30-45cm) (45-60cm) (0-15cm) (15-30cm) (30-45cm) (45-60cm)  Operating Temperatures (°C) 30 30 30 30 35 35 35 35 40 40 40 40  Loam S o i l a t d i f f e r e n t t e m p e r a t u r e s u n d e r  Volumetric Moisture Content (%) [before irrigation] 33.2 40.0 48.8 51.9 36.7 36.3 45.9 51.1 37.7 33 . 8 47.0 49.8  Volumetric Moisture Content (%) [after Irrigation] 50.3 45.8 49.3 52.0 50.2 44.3 46.8 51.8 48.0 43 .2 49.2 51.3  Percent Stored  (%)  17 .1 5.8 0.5 0.1 13 . 5 8.0 0.9 0.7 10.3 9.4 2.2 1.5  Volume o f irrigation water stored (L) 25.7 8.7 0.8 0.2 20.3 12.0 1.4 1.0 15.5 14.1 3.3 2.3  Surface  Total Percent o f applied Total water i n Volume entire Applied root-zone  (%)  67.50 22.89 1.97 0.39 53.29 31.58 3.55 2.76 40.66 37.11 8.68 5.92  (%)  92.76  91.18  92.37  B 30 Degree Celsius HI 35 Degree Celsius B 40 Degree Celsius  Dl (0-15 cm)  D2 (15-30 cm)  D3 (30-45 cm)  D4 (45-60 cm)  Soil Depths  Figure  4.8 Percent of Total Applied Depths of Silt Loam Soil under Surface Irrigation  Water Stored at Different System.  in Different Temperatures  A t 30 °C, 25.7 w a t e r was  °C  (15.5  different  ( e q u i v a l e n t t o 67.50%) o f t h e t o t a l  L) .  soil  The  volumes of a p p l i e d  layers  of s i l t  loam  soil  water a t 30,  stored 35,  i r r i g a t i o n a r e s u m m a r i z e d i n T a b l e 4.9.  in  lower s o i l  l a y e r s the p a t t e r n again reversed  was  stored  temperatures. D  2  at  at  higher  temperatures  as  The p e r c e n t a g e o f t o t a l 30,  respectively.  35,  and  The  40  °C  was  percentage  moisture content w i t h the increase °C was  that  (20.3 L) a n d a p p r o x i m a t e l y 40% more t h a n t h a t a t  under s u r f a c e  depth  applied  s t o r e d i n l a y e r D l , w h i c h i s a b o u t 2 0% more t h a n  s t o r e d a t 35 °C 40  L  27.52 a n d 14.90  in  and  four 40  °C  However,  a n d more w a t e r  compared  to  lower  a p p l i e d water stored i n  about  increase  23, in  31,  and  the  37  %,  volumetric  i n t e m p e r a t u r e f r o m 3 0 t o 40  a n d 38.32 % f o r t e m p e r a t u r e i n c r e m e n t o f  35 t o 40 °C a n d 30 t o 40 °C, r e s p e c t i v e l y .  Soil layer D, 3  stored  a b o u t 44 a n d 77 % more w a t e r a t 35 a n d 40 °C as c o m p a r e d t o t h a t it  s t o r e d a t 30 °C.  °C was  about  The 1.0, moved  1.4,  a n d 3.3  L a t 30,  deeper  i n depth D  35, a n d 40 °C, r e s p e c t i v e l y .  layers  40  L, r e s p e c t i v e l y .  volumes of a p p l i e d water s t o r e d  a n d 2.3 to  0.8,  The v o l u m e o f w a t e r s t o r e d a t 30, 35 a n d  at higher  temperatures  were  4  0.2,  More w a t e r  than  at  lower  t e m p e r a t u r e s , a b o u t 86 % a t 35 °C, and o v e r 93 % more a t 40 °C as c o m p a r e d t o 3 0 °C.  4.4.1.2  T r i c k l e I r r i g a t i o n System  Sandy  loam  soil  again  stored  the major  irrigation  water a p p l i e d through t r i c k l e  15 cm s o i l  l a y e r f o r a l l the three  4.9).  However,  t h e amount o f a p p l i e d  applied  water,  volume o f water soil  at  30,  illustrated  water  stored  irrigation.  respectively.  stored  35,  t o 61.58,  (Figure  i n Di was  In layer B  and  40  i n Figure  °C  4.9,  under more  However,  surprisingly  contrary  soil  the  1  Nevertheless,  L)  under  i n layers D, 3  w a t e r was s t o r e d a t h i g h e r  was  tabulates  the  o f sandy  loam  irrigation. stored  As  at  lower  temperature i n top l a y e r to  4  layers  water  surface  (Di) .  irrigation,  the  (15-30 cm) was a l m o s t t h e  a l l the and D  a n d 46.58 % o f  4.10  trickle  volume o f w a t e r s t o r e d i n second l a y e r (3.90-4.05  50.53,  Table  i n different  t e m p e r a t u r e s a s compared t o h i g h e r  same  i n the top  o f a p p l i e d w a t e r s t o r e d a t 30, 35, a n d 40 °C w e r e 11.70.  9.60, a n d 8.85 L, e q u i v a l e n t total  irrigation  of the  temperatures t e s t e d  lower than t h a t s t o r e d under s u r f a c e volumes  portion  three  temperatures.  the pattern reversed  temperatures.  In layer D  3  a n d more about  37  a n d 48 % more w a t e r was s t o r e d a t 35 a n d 40 °C, t h a n t h a t  stored  a t 3 0 °C, r e s p e c t i v e l y .  stored  The i n c r e m e n t a l  change i n w a t e r  a t 40 °C was a b o u t 17% o v e r t h a t a t 35 °C. the volumes  I n case of l a y e r  D, 4  o f s t o r e d w a t e r were 1.2, 2.1, a n d 2.25 L a t 30, 35,  a n d 40 °C, r e s p e c t i v e l y .  A t 40 °C, o v e r 46 % more w a t e r  stored  as c o m p a r e d t o t h a t a t 3 0 °C, a n d c l o s e t o 7 % more a s c o m p a r e d t h a t a t 35 °C.  T a b l e 4.10  Soil Type  P e r c e n t o f T o t a l A p p l i e d W a t e r S t o r e d i n e a c h D e p t h i n S a n d y Loam S o i l a t D i f f e r e n t Temperatures under T r i c k l e I r r i g a t i o n System.  Soil Depth (cm)  Di D D D Di Sandy D Loam D D Di D D D 2  3  4  2  3  4  2  3  4  (0-15cm) (15-30cm) (30-45cm) (45-60cm) (0-15cm) (15-30cm) (30-45cm) (45-60cm) (0-15cm) (15-30cm) (30-45cm) (45-60cm)  Operating Temperature s (°C)  Volumetric Moisture Content (%) [before irrigation]  Volumetric Moisture Content {%) [after Irrigation]  30 30 30 30 35 35 35 35 40 40 40 40  19.3 20.4 24.0 39.0 18.9 21.0 24.1 38.7 18. 6 20.2 24.8 37.9  27.1 23 .1 25.2 39.8 25.3 23 .7 26.0 40.1 24.5 22 . 8 27.1 39.4  Percent Stored (%) 7 . 80 2.70 1.20 0.80 6 .40 2 .70 1.90 1.40 5.90 2 . 60 2.30 1.50  Volume o f irrigation water stored (L) 11.70 4.05 1.80 1.20 9.60 4.05 2 .85 2 .10 8.85 3 .90 3 .45 2.25  Total Percent o f applied water i n Total entire Volume root-zone Applied (%) (%) 61.58 21.32 9.47 6.32 50.53 21.32 15.00 11.05 46.58 20.53 18.16 11.84  98.7  97.9  97.1  70  • 30 Degree Celsius Œl 35 Degree Celsius B 40 Degree Celsius  60 50  I"S.  40  c < 30  1  o H O 20  1 ë 10 0 D l (0-15 cm)  D2 (15-30 cm)  D3 (30-45 cm)  D4 (45-60 cm)  Soil Depths  Figure  4.9 Percent of Total Applied Water Stored Depths of Sandy Loam Soil at Different under Trickle I r r i g a t i o n System.  in  Different Temperatures  Simxlar to surface  irrigation,  water i n s i l t  loam s o i l  the  (Di) as shown i n F i g u r e  in  top l a y e r  l a y e r Di a t 30,  which  are  35,  60.79,  respectively.  under  the major p o r t i o n of a p p l i e d  and  56.05,  As  trickle  40  and  i r r i g a t i o n was 4.10.  The  °C w e r e 2 3 . 1 , 39.47  %  of  volume  21.3,  total  stored i n  and  stored 15.0  applied  i n the p r e v i o u s experiments,  the  water,  lower  t e m p e r a t u r e , t h e h i g h e r the volume o f w a t e r s t o r e d i n t h e layer  (Di) .  The  The p e r c e n t a g e i n c r e a s e at  35  °C  summarizes soil  was  l a y e r s of s i l t  D,  and D )  in  these  3  over  t h e volumes  irrigation.  deeper  t o 40  29%  loam s o i l  layers. 2  °C a n d  more w a t e r was In layer D  °C.  as  °C.  a p p l i e d water storage w i t h i n  compared  to  40  °C.  Table  a t 30, 35, a n d 40 °C u n d e r  4  The  percentage  f r o m 3 0 t o 3 5 °C was 3 0 t o 40 3  °C.  increase  3 0.2  T h e r e was  4.11  trickle (D , 2  in  water  %, a n d 2 5 a n d n o t any  48%  change i n  a t 30 a n d 35 °C, h o w e v e r a b o u t 21.45  the increase  i n w a t e r s t o r a g e was  33.28 % f r o m  30°  58.29 % f r o m 35° t o 40 °C, a n d 37.49 % f r o m 30° t o  40  These t e s t s c l e a r l y demonstrate t h a t t h e t e m p e r a t u r e has  zone.  %  s t o r e d a t 40 °C t h a n t h a t s t o r e d a t 3 0 o r 3 5 °C.  r e m a r k a b l e e f f e c t on t h e d i s t r i b u t i o n o f s o i l root  a t 40  of a p p l i e d water s t o r e d i n four d i f f e r e n t  water storage i n l a y e r D  t o 35 °C,  i n total  stored  w i t h h i g h e r temperatures f a v o r i n g the water storage  4  35  first  Once a g a i n t h e p a t t e r n r e v e r s e d i n l o w e r l a y e r s  storage i n layer D for  the  t o p l a y e r s t o r e d a b o u t 8 % more w a t e r a t 3 0 °C  a s c o m p a r e d t o 35 °C, a n d 35 % more t h a n t h a t  Di  L,  water w i t h i n  a  the  T a b l e 4.11 V o l u m e t r i c M o i s t u r e C o n t e n t i n S i l t I r r i g a t i o n System.  Soil Type  Soil Depth (cm)  D! D D D Di Silt D Loam D D D D D D 2  3  4  2  3  4  x  2  3  4  (0-15cm) (15-30cm) (30-45cm) (45-60cm) (0-15cm) (15-30cm) (30-45cm) (45-60cm) (0-15cm) (15-30cm) (30-45cm) (45-60cm)  Loam S o i l a t d i f f e r e n t t e m p e r a t u r e s u n d e r  Operating Temperatures (°C)  Volumetric Moisture Content {%) [before irrigation]  Volumetric Moisture Content (%) [after Irrigation]  Percent Stored (%)  30 30 30 30 35 35 35 35 40 40 40 40  36.1 39.7 45.2 49.5 35.7 40.1 44.9 46.0 35.9 39.5 44.6 49.9  51.5 44.1 47.4 51.0 49.9 46.4 47.1 47.0 45.9 47.9 47 .4 52 .3  15.4 4.4 2.2 1.5 14.2 6.3 2.2 1.0 10.0 8.4 2.8 2.4  Volume o f irrigation water stored (L) 23 .1 6.6 3.3 2.3 21.3 9.5 3.3 1.5 15.0 12.6 4.2 3.6  Trickle  Total Percent o f applied Total water i n Volume entire Applied root-zone (%) (%) 60.79 17.37 8.68 5.92 56.05 24.87 8.68 3.95 39.47 33.16 11.05 9.47  92 . 8  93 . 6  93 .2  70 60 50  .1  40  "B.  30 o H 20  S ë 10  1 i  Oh  0  • i  va D l (0-15 cm)  • D2 (15-30 cm)  D3 (30-45 cm)  Illlll  • 30 Degree Celsius E 35 Degree Celsius B 40 Degree Celsius  -  D4 (45-60 cm)  Soil Depths  Figure 4.10  Percent of Total Applied Depths of Silt Loam Soil under Trickle Irrigation  Water Stored at Different System.  in Different Temperatures  In  both  systems, the Di  the  soils,  under  surface  and  trickle  irrigation  the major p o r t i o n of the a p p l i e d water accumulated i n  top l a y e r was  (0-15 cm)  inversely  and t h e volume o f w a t e r s t o r e d i n l a y e r  proportional  to  temperature.  With  lower  t e m p e r a t u r e s more w a t e r a c c u m u l a t e d i n l a y e r Di as c o m p a r e d t o higher temperatures.  W i t h i n deeper  layers  (D , D , 2  3  and D )  the  4  w a t e r s t o r a g e p a t t e r n r e v e r s e d from t h a t i n l a y e r Di, and h i g h e r temperatures layers.  favored  accumulation  Furthermore,  in  sandy  of  water  loam  i r r i g a t i o n most o f t h e a p p l i e d w a t e r was and  only  very  layer D.  quantities  In comparison,  4  w a t e r was trickle  small  and t r i c k l e  soil  these  under  layers  with  a s i g n i f i c a n t p o r t i o n of the  as w e l l  as  in silt  lower surface  s t o r e d i n the top  i n lower  accumulated i n lower layers  irrigation  in  i n sandy loam  none  under  under  surface  irrigation.  The p o s s i b l e r e a s o n s f o r t h e a b o v e r e s u l t s c o u l d be due the  temperature  liquid  in  applied  loam s o i l  soil  layer  phase,  affects  by  on  i t s effect  soil  water  on v i s c o s i t y  movement and  both  surface  in  to the  tension,  a n d i n t h e v a p o r p h a s e b y i t s l a r g e e f f e c t on t h e v a p o r p r e s s u r e of  water.  4.4.2  Discussion As e v i d e n t f r o m t h e r e s u l t s ,  the lower the temperature, the  h i g h e r t h e v o l u m e o f w a t e r s t o r e d i n t h e t o p 15 c e n t i m e t e r l a y e r (Dx)  f o r both  soils  and  under  both  irrigation  methods.  The  patterns  r e v e r s e d i n the lower l a y e r s - D , 2  higher  volumes  of  irrigation  water  were  D,  and D  3  stored  temperatures i n b o t h s o i l s under s u r f a c e and t r i c k l e systems.  More water was  4  -where  at  higher  irrigation  s t o r e d i n the lower l a y e r s a t h i g h e r  temperatures as compared t o lower temperatures because  of the  g r e a t e r movement of water t o lower l a y e r s . Several  soil  water  temperature s e n s i t i v e c h a r a c t e r i s t i c s  may have c o n t r i b u t e d i n t o these t r e n d s .  Temperature  dependence  of the v i s c o s i t y of the s o i l water may have p l a y e d a major in i t . hence  S o i l water v i s c o s i t y decreases as temperature i n c r e a s e s increasing  the  hydraulic  c o n d u c t i v i t y of  H y d r a u l i c c o n d u c t i v i t y and the s o i l proportional  (Jackson, 1963).  He  a l s o observed  d i f f e r e n c e s between s o i l water d i f f u s i v i t i e s  42.5  °C.  agreement  The  results  with  other  determined d i f f u s i v i t y  and  t r e n d s of t h i s  studies,  such  in a silt  the  soil.  temperature a r e i n v e r s e l y  fold  as  two-to-three a t 5 °C  diffusivity  increased with  Stewart  c l a y loam  temperature  (1962),  soil  at  a t a l l water  i n temperature.  diffusivity conductivity  may with  be  increase  7Any  a t t r i b u t e d to temperature.  The  conducted by H a r i d a s a n and Jensen i n d i c a t e that  hydraulic  an  i n the  increase results  (1972)  of  water  levels.  soil  with water  i n hydraulic the  and R a h i and  c o n d u c t i v i t y was  who  different  R a h i and Jensen (1975) a l s o found i n c r e a s e s i n d i f f u s i v i t y increases  and  study are a l s o i n  temperatures r a n g i n g from 8° t o 40 °C, and found t h a t s o i l  (1975)  role  studies Jenses  temperature  dependent  and  temperature  the increase  could  in" saturated  soil  dependence  in  influenced  (1915), P i l l s b u r y  (1950),  t h a t t h e e f f e c t o f t e m p e r a t u r e on  saturated hydraulic conductivity i n s o i l temperature  rise  The r e s i s t a n c e  i s significantly  Bouyoucos  (1982), r e p o r t e d  a  i n v i s c o s i t y of  t h e temperature change.  by temperature o f t h e s o i l . and C o n s t a n t z  with  be a t t r i b u t e d t o a d e c r e a s e  s o i l water accompanying to moisture flow  i n conductivity  c a n be e x p l a i n e d b y t h e  of the v i s c o s i t y  of water.  A  simple  a p p r o a c h i n d e s c r i b i n g t h i s r e l a t i o n s h i p c a n be t h e p a r t i t i o n i n g of  the saturated  hydraulic  conductivity,  K, s  i n the following  manner :  Ks = K * ( £ %  (4.8)  Where "K" i s t h e i n t r i n s i c p e r m e a b i l i t y the Darcy's  (K) b y  acceleration water  (T|/pg) , "p" i s t h e d e n s i t y  "g" i s  due t o g r a v i t y , a n d "T|" i s t h e v i s c o s i t y  of the  1937).  of the l i q u i d  therefore  by m u l t i p l y i n g  of water,  (Muskat,  density  obtained  t h e magnitude  The  temperature  c o e f f i c i e n t of  i s a p p r o x i m a t e l y 10" to which  this  4  Kg/Liter  the  p e r °C,  c o e f f i c i e n t might  be  expected to influence the hydraulic c o n d u c t i v i t y i s n e g l i g i b l e i n the s o i l saturated the  system.  On t h i s b a s i s , t h e e f f e c t o f t e m p e r a t u r e on  f l o w may be a t t r i b u t e d s o l e l y t o a s i m p l e  c h a n g e o f "T|" w i t h  temperature.  Unsaturated  r e l a t i o n of conductivity  c a n b e p a r t i t i o n e d i n a s i m i l a r manner a s "K " a s b e l o w : s  K  w h e r e "K e)" r(  ( 6 )  =K  r ( 6 )  (4.9)  i s t h e r e l a t i v e p e r m e a b i l i t y a s a f u n c t i o n o f "0",  the v o l u m e t r i c water content 4.9  *K*(^)  (Muskat a n d M e r e s , 1 9 3 6 ) .  Equation  i n d i c a t e s t h a t a t a g i v e n v a l u e o f "0", "K ).K.pg" s h o u l d b e r(e  i n d e p e n d e n t o f t h e t e m p e r a t u r e , a n d t h a t t h e change i n "K e)" (  temperature  should  be  proportional  to  the  with  temperature  coefficient of "l/r|". The soil  water  surface also  other  important  distribution  tension.  decreases  hydraulic  f a c t o r t h a t may b e r e s p o n s i b l e f o r t h e  Like as  patterns soil  water  temperature  i n this  study  viscosity,  increases  conductivity, permeability,  may b e t h e  surface  which  tension  affects the  and pressure  gradient.  The  b u l k o f l i q u i d w a t e r must h a v e moved a s c a p i l l a r y w a t e r  due  to differences i n surface tension a t different  If  we  consider  gradients  the effect  i n the l i q u i d  hydrostatic pressure unsaturated  soil  of temperature  and vapor  flow  temperatures.  on t h e p r e s s u r e  i n unsaturated  s o i l , the  "P" w i t h r e s p e c t t o a f r e e w a t e r s u r f a c e i n  c a n be w r i t t e n as below:  2S  P=—  r  (4.10)  where  "S"  i s surface  tension  of  water,  " r " i s radius  curvature of the water surface i n the s o i l pores 1952). is  of  (Gurr e t . a l . ,  S i n c e "S" d e c r e a s e s w i t h i n c r e a s i n g t e m p e r a t u r e , a n d " r "  assumed  t o have  increasing  a constant value,  temperature.  When  "P" w i l l  temperature  increase  with  gradients  were  e s t a b l i s h e d i n t h e s o i l s , p r e s s u r e g r a d i e n t s r e s u l t e d a n d moved water  i n the d i r e c t i o n  W i l k i n s o n and K l u t e ' s pressure  head  due  of decreasing temperature (1962)  e x p l a n a t i o n f o r t h e changes i n t h e  t o temperature  changes  was  t e m p e r a t u r e on t h e e n t r a p p e d a i r a n d a i r - w a t e r Temperature the for  differences  (downwards).  the effect  of  interface.  induced vapor p r e s s u r e g r a d i e n t s ,  d r i v i n g f o r c e f o r w a t e r v a p o r f l o w , may a l s o be r e s p o n s i b l e more  water  temperatures. temperatures  movement Vapor  because  hence  of  be  layers higher  at  higher  at  higher  of  vapor  ( C a r y , 1 9 6 6 ) , a n d w i l l be l o w e r a t l o w e r  causing  (cold areas).  to  i s o t h e r m a l water  vapor  flow  towards  decreasing  The c o n t r i b u t i o n o f w a t e r v a p o r  flux  f l u x i n u n s a t u r a t e d s o i l s may b e  a c o n t r i b u t i n g factor i n the s o i l different  will  soil  t h e e x p o n e n t i a l dependence  temperatures the t o t a l  deeper  pressure  p r e s s u r e on t e m p e r a t u r e temperatures  into  water d i s t r i b u t i o n  trends at  temperatures.  Robert  Gardner  (1954),  i n h i s study  found  that  the  soil  moisture suction  (matric p o t e n t i a l ) decreased w i t h the increase  in  The d e c r e a s e i n s o i l m o i s t u r e t e n s i o n may h a v e  temperature.  caused the temperature  induced moisture gradients i n the s o i l s  at  higher  temperatures.  have been on t h e s o i l  The d i r e c t  water  effect  of temperature  t e n s i o n and an i n d i r e c t  effect  may may  have been t h e temperature i n d u c e d m o i s t u r e g r a d i e n t s . Furthermore, irreversible) different dependence  structural  i n the s o i l  temperatures of  soil  water d i s t r i b u t i o n  changes  matrix influencing  may  have  hydraulic patterns.  contributed  conductivity  (reversible  and  the flow paths at to a and  temperature  over  a l l soil  4.4.3  S o i l Water Content  The silt °C) to  volumetric water content  loam s o i l s  profiles  i l l u s t r a t e the l a t e r a l soil  depth.  zero  source;  spatial  Moisture  volumetric s o i l moisture Point  systems were  distribution  content  developed  of a p p l i e d water  profiles  (0) o n t h e a b s c i s s a c o r r e s p o n d s  25 represents  (30, 3 5 , a n d 40  represent  l a t e r a l l y around t h e i r r i g a t i o n  east  and south  ( F i g u r e 3.3 b) ; -25 r e p r e s e n t s  the  source.  to the i r r i g a t i o n  t h e a v e r a g e o f two r e a d i n g p o i n t s  l o c a t e d a t 25 cm r a d i u s  source  f o r sandy loam and  a t three d i f f e r e n t temperatures  under s u r f a c e and t r i c k l e i r r i g a t i o n  along  3)  Profiles  of the  the average  p o i n t s 4 and 5 west and n o r t h o f t h e i r r i g a t i o n  (2 a n d  irrigation of reading  s o u r c e a t 2 5 cm  r a d i u s ; 50 r e p r e s e n t s t h e a v e r a g e o f r e a d i n g p o i n t s 6 a n d 7 e a s t of the i r r i g a t i o n  s o u r c e a t 50 cm r a d i u s ; a n d -50 r e p r e s e n t s t h e  average o f r e a d i n g p o i n t s 8 and 9 west o f t h e i r r i g a t i o n at  50 cm r a d i u s  ( F i g u r e 3.3b).  at  t h e o r d i n a t e was o b t a i n e d b y s u b t r a c t i n g t h e  volumetric moisture moisture  content.  4.4.3.1  Surface  In  content  Irrigation  under s u r f a c e  content  pre-irrigation  from t h e p o s t - i r r i g a t i o n  volumetric  System  sandy loam s o i l ,  w a t e r was s i g n i f i c a n t l y  The v o l u m e t r i c m o i s t u r e  source  the l a t e r a l different  irrigation.  distribution  i n Di, D , 2  D, 3  of i r r i g a t i o n and D  4  layers  20 18  ^ 1 6 -i ^ 14 9 10 * 8 •3 6-1 Dl  0  30 Degree Celsius 35 Degree Celsius - - - - - - 40 Degree Celsius  -50  -25  25  50  -50  -25  25  50  -50  -25  25  50  -25 0 25 Distance from Irrigation Source (cm)  50  -50  F i g u r e 4.11 V o l u m e t r i c M o i s t u r e C o n t e n t P r o f i l e s o f S a n d y Loam S o i l a t D i f f e r e n t Depths and Temperatures under Surface I r r i g a t i o n .  The on  effects  lateral  surface  of different  soil  moisture  irrigation  all  four  the  irrigation  temperatures  distribution  i n sandy  a r e shown i n F i g u r e 4.11.  source and decreased l a t e r a l l y s o u r c e i n c r e a s e d owing  soil.  w e r e more o r l e s s  The p r o f i l e s and D ,  2  however  3  distribution was  loam  almost  layer  D  4  of a p p l i e d water.  just  below  as t h e d i s t a n c e  t o w a t e r movement i n  symmetric  showed  under  As e x p e c t e d , i n  l a y e r s maximum m o i s t u r e c o n t e n t was f o u n d  from t h e i r r i g a t i o n  D,  (30, 35, a n d 40 °C)  an  The l a t e r a l  f o r layers Di,  asymmetric  lateral  s p r e a d i n l a y e r Di  t h e same f o r a l l t e m p e r a t u r e s , h o w e v e r i n l a y e r  volumetric s o i l  D  2  m o i s t u r e was h i g h e r a t 40 °C a s c o m p a r e d t o 3 0°  a n d 35 °C.  S o i l m o i s t u r e was a maximum j u s t b e l o w t h e s o u r c e o f  irrigation  i n layer D  and  35  °C)  t h e r e was  moisture distribution. asymmetric, three  3  a t 40 °C, a n d a t l o w e r t e m p e r a t u r e s n o t any s i g n i f i c a n t  The m o i s t u r e d i s t r i b u t i o n  and t h e h i g h e s t s o i l  o p e r a t i n g temperatures  temperature  increased,  in  lateral  i n layer D  4  was  moisture content a t a l lthe  was  s o u r c e , w i t h maximum v a l u e a t 40 °C. when  change  (30  just  below  the  irrigation  This i s reasonable  i t decreased  because  the v i s c o s i t y  and  s u r f a c e t e n s i o n o f water and hence i n c r e a s e d t h e c o n d u c t i v i t y o f soil.  Silt  significantly different soil  loam  soil,  like  t h e sandy  varied lateral distribution l a y e r s under  loam  soil,  showed  of i r r i g a t i o n water i n  surface irrigation.  30 Degree Celsius ^ 35 Degree Celsius • 40 Degree Celsius  25 20 15 10 o >  Dl  5 -50  -25  25  50  12 10  •3  4  D2 -50  -25  25  50  -50  -25  25  50  -25 0 25 Distance from Irrigation Source (cm)  50  12 10  « o >  4 2 0 10  t  8 *—^  O  *3 >  6 4 2 0 -50  F i g u r e 4.12 V o l u m e t r i c M o i s t u r e C o n t e n t P r o f i l e s o f S i l t Loam S o i l a t D i f f e r e n t Depths and Temperatures under Surface I r r i g a t i o n .  Figure  4.12  temperatures  ( 3 0 , 35, a n d 40  movement i n s i l t loam  soil,  illustrates  t h e maximum m o i s t u r e  laterally  irrigation erratic  content  moisture  a t 3 0 °C.  symmetric  decreasing  lateral  soil  in D  laterally source.  3  as  and D  was  the  However,  moisture layers  4  distance  i n layer  D  2  just  In the top below the  distribution  with  soil  increased  at  30  °C  from  the  the d i s t r i b u t i o n  was  distribution,  symmetric  w i t h t h e maximum j u s t b e l o w t h e i r r i g a t i o n  the d i s t r i b u t i o n  minimum a t t h e f a r t h e s t p o i n t s f r o m t h e i r r i g a t i o n F i g u r e 4.11, i n d e p t h D i , t h e s o i l w a t e r p r o f i l e s almost  ponding  t h e same f o r a l l t e m p e r a t u r e s  force behind the s o i l  soil was  source and  source. lateral  From spread  because o f t h e s u r f a c e  o f t h e i r r i g a t i o n water and t h e g r a v i t a t i o n a l  being the driving  was  moisture  a t 35 a n d 40 °C w i t h a m i x e d p a t t e r n o f l a t e r a l but  just  and decreased  moisture  was  moisture  was n o t a l w a y s  content  Lateral  different  U n l i k e sandy-  source a t a l l the three temperatures, except  somewhat  on  of  source i n a l l the four l a y e r s .  (Di) t h e maximum  irrigation  °C)  effects  loam under s u r f a c e i r r i g a t i o n .  below the i r r i g a t i o n layer  the  potential  w a t e r movement.  It is  a l s o obvious from t h e f i g u r e t h a t t h e h i g h e r v o l u m e t r i c m o i s t u r e c o n t e n t s i n p e r c e n t were a t t h e l o w e r t e m p e r a t u r e s and  the lowest volumetric moisture  c o n t e n t p e r c e n t was a t t h e  higher  temperature  layers  (D , D , a n d D ) f o r t h e r e a s o n s d i s c u s s e d i n t h e p r e v i o u s  section.  2  3  (40 °C) .  (30 a n d 35 °C)  4  The t r e n d r e v e r s e s  i n the lower  The o v e r a l l loam s o i l soil,  e x c e p t f o r t h e symmetry o f t h e p r o f i l e s .  cracks,  pathways  biopores,  might  distribution  4.4.3.2  p a t t e r n s w e r e t h e same a s i n c a s e o f t h e s a n d y  have  and  other  prevented  In s i l t  loam  water  flow  preferential  the  uniform  and  symmetric  of i r r i g a t i o n water.  Trickle  Irrigation  System  Under t r i c k l e i r r i g a t i o n t h e l a t e r a l m o i s t u r e d i s t r i b u t i o n in  sandy loam s o i l  layers,  with  maximum m o i s t u r e c o n t e n t j u s t b e l o w t h e i r r i g a t i o n s o u r c e .  The  temperature e f f e c t  was s y m m e t r i c i n a l l t h e f o u r  on l a t e r a l s o i l m o i s t u r e d i s t r i b u t i o n  i nthe  s a n d y l o a m u n d e r t r i c k l e i r r i g a t i o n i s d e p i c t e d i n F i g u r e 4.13. There  was n o t a n y s i g n i f i c a n t  moisture d i s t r i b u t i o n  difference  i n the top three  i n horizontal  layers  (Di, D ,  irrigation  source.  Soil  sandy  below the  However, i n t h e  (D ) a t 35 °C t h e l a t e r a l s o i l m o i s t u r e d i s t r i b u t i o n 4  was n o t s y m m e t r i c a l . to  3  m o i s t u r e d e c r e a s e d l a t e r a l l y as t h e  d i s t a n c e from t h e i r r i g a t i o n source i n c r e a s e d . lowest layer  and D )  2  w i t h t h e h i g h e s t m o i s t u r e c o n t e n t , as e x p e c t e d , j u s t  soil  loam  distribution  soil  In s i l t with  (Figure  loam s o i l  well  4.14).  t h e p a t t e r n was  symmetric l a t e r a l In a l l the four  soil  similar  moisture  layers,  soil  m o i s t u r e was a maximum j u s t b e l o w t h e c e n t e r a n d d e c r e a s e d w i t h the  distance  significant  from  the i r r i g a t i o n source.  difference  among t h e f o u r  layers.  i n soil  There  was n o t a n y  moisture d i s t r i b u t i o n  pattern  DistancefromIrrigation Source (cm)  F i g u r e 4.13  V o l u m e t r i c M o i s t u r e C o n t e n t P r o f i l e s o f S a n d y Loam S o i l a t D i f f e r e n t Depths and Temperatures under Trickle Irrigation.  20 15  o  10  o >  5  •30 Degree Celsius 35 Degree Celsius • 40 Degree Celsius  Dl  0 -50  -25  25  50  -50  -25  25  50  -25 0 25 Distance from Irrigation Source (cm)  50  o  >  u  -50  F i g u r e 4.14 V o l u m e t r i c M o i s t u r e C o n t e n t P r o f i l e s o f S i l t Loam S o i l a t D i f f e r e n t Depths and Temperatures under Trickle Irrigation.  However, a s i n t h e s a n d y l o a m s o i l the moisture In the  d i s t r i b u t i o n was  sandy loam and s i l t  soil  water p r o f i l e  irrigation. was  little  s k e w e d a t 3 5 °C.  loam s o i l s u n d e r t r i c k l e  trends  were  reasons,  t h e same a s  irrigation,  with  surface  However t h e l a t e r a l d i s t r i b u t i o n i n s a n d y l o a m  different,  content  due f o r some unknown  as s i l t  percent  loam s o i l had h i g h e r v o l u m e t r i c  a t -50  and  50  compared t o sandy loam s o i l .  centimeter  moisture  from the e m i t t e r  flow.  as  the p o s s i b l e reason  sandy  gravitational soil  being  main  driving  loam  potential  soil being  fine-textural  with  soil  f o r c e , hence  c o u l d be bigger  the d r i v i n g and  more  w a t e r than i n sandy loam s o i l . decrease  soils  loam s o i l , where t h e c a p i l l a r y f o r c e s dominate t h e  Therefore,  soils,  as  I n g e n e r a l , g r a v i t y f o r c e s have a  l i m i t e d e f f e c t on t h e w a t e r movement i n t h e f i n e - t e x t u r a l s u c h as s i l t  soil  pores  and  f o r c e and s i l t  loam  capillary  lateral  the t e x t u r e of  soil  forces being  movement  The s a n d y l o a m s o i l  i n volumetric moisture  content percent  of  the  had a  the soil rapid  laterally  away  f r o m t h e a p p l i c a t i o n s o u r c e due t o i t s h i g h e r c o n d u c t i v i t y w h i l e the  silt  loam  capillarity, moisture  had  soil, a  with  more  content percent  lower  gradual  conductivity decline  in  the  and  higher  volumetric  l a t e r a l l y away f r o m t h e p o i n t  source.  4.4.4  soil  Wetting F r o n t s The w e t t i n g f r o n t ,  t h e i n d i c a t i v e o f t h e l o c a t i o n where t h e  moisture  equals  initial  content  moisture  describe  the  distribution  content  about  2  percent  (before i r r i g a t i o n )  extent  of  the  soil  under  different  more  has  than  been used  volumetric moisture conditions.  To  3  and  and D  4  i n both s o i l s  trickle  (sandy l o a m and s i l t  i r r i g a t i o n methods a t 3 0°,  p l o t s w e r e c o n s t r u c t e d ( f i g u r e s 4.15 s o f t w a r e p a c k a g e SURFER.  The  to  content  illustrate  v o l u m e t r i c water content d i s t r i b u t i o n p a t t e r n s i n depths D,  the  Di,  D, 2  loam) u n d e r s u r f a c e  3 5°, a n d  40  t h r o u g h 4.34)  °C,  contour  using graphic  c o n t o u r l i n e s o b t a i n e d by  Kriging  ( G r i d d i n g M e t h o d ) , show t h e r a d i a l l o c a t i o n s o f e q u a l v o l u m e t r i c moisture content percentages the p l o t s , extent  of  w i t h i n the wetted s o i l  the contour w i t h small v e r t i c a l the w e t t i n g f r o n t  that temperature  lines  i n that particular  volume.  In  represent  the  soil  and under t h a t i r r i g a t i o n system.  percent volumetric moisture content a f t e r  both s o i l s .  i n a l l cases  experiments.  at  maximum found  experiments  B u t t h e i r r i g a t i o n s o u r c e d i d n o t b e h a v e as  i d e a l i z e d p o i n t source m a j o r i t y of  The  i r r i g a t i o n was  j u s t below the i r r i g a t i o n source i n the m a j o r i t y of for  depth,  an  even though i t d i d i n the  4.4.4.1  Surface I r r i g a t i o n  The  water  application  spread  w h i c h was  temperatures, minute) the  over  the  right  at  because  the  was much g r e a t e r  recommended  range  soil the  surface center  application  than  the  (Walker,  from  the  i n both rate  soils  (29  at  rate  but  1989)  caused  of a l l  liters  infiltration which  point  per  within surface  ponding.  4.4.4.1.1 In about  Sandy Loam  the  case  3 minutes  of for  Soil sandy  a l l  loam  contours percent of  point)  in  the  along that  30 °C h a s  at  plots  content  a l l show  line.  contours  close  to  that  centimeter  the  radius  and 31-28%; and w i t h i n a n d 28-26% a t The the  to  effect  the  tension  were  the  each other  the  at  the  center on  moisture  the  content  d e p t h Di i n the  as  compared to  content  percent  ranged between  50 c e n t i m e t e r  that  show  A close observation of  center  was  Numbers  volumetric 4.15,  time  case  35° and  the  plots  within  25  36-33%,  35-33%,  r a d i u s were 33-29%,  33-28%,  3 0 ° , 3 5 ° , a n d 40 ° C , r e s p e c t i v e l y .  differences  within  the  Results  temperatures.  volumetric moisture from  recession  percent  Contour p l o t  40 ° C , w h i c h w e r e m o r e s p a c e d . reveals  the  temperatures.  maximum v o l u m e t r i c m o i s t u r e (application  soil,  same of  radii  in  volumetric  from  the  temperature  point on  soil  and h y d r a u l i c c o n d u c t i v i t y .  moisture of  content  percent  a p p l i c a t i o n may b e  water  viscosity,  due  surface  Figure 4.15 Volumetric Moisture Content (!) Distribution in Sandy Loam Soil in Layer DI (0-lBcm) under Suaface Irrigation Sysytem. The mibers on the contours indicate the volumetric moisture content (!)  The  maximum r a n g e was a t 30 °C a n d t h e minimum a t 40 °C,  w h i c h i n d i c a t e d t h a t more w a t e r i n f i l t r a t e d at  i n t o deeper  h i g h e r temperatures than a t lower temperature.  layers  The c o n g e s t e d  c o n t o u r p l o t o f 30 °C a n d more s p a c e d c o n t o u r s i n c a s e o f 3 5° a n d 40 °C i n d i c a t e d t h a t t h e l a t e r a l applied  water  were g r e a t e r  and t h e v e r t i c a l  a t 35° a n d 40  °C  movements o f  than  a t 30  t h e r e f o r e 3 0 °C c o n t o u r s w e r e n a r r o w b e c a u s e o f l e s s w a t e r movement  horizontal  a n d c o n t o u r s w e r e more s p a c e d a t 3 5° a n d 40 °C  b e c a u s e o f more h o r i z o n t a l temperatures.  °C,  movement  of water  i n soil  a t those  The l o w e r v o l u m e t r i c m o i s t u r e c o n t e n t r a n g e s a t  35° a n d 40 °C i n d i c a t e d  that  the v e r t i c a l  movement  of applied  w a t e r was a l s o g r e a t e r a t t h o s e t e m p e r a t u r e s . F i g u r e 4.16 shows t h e w e t t i n g f r o n t s at  30°, 35°, a n d 40 °C i n d e p t h D  obvious  from  irrigation infiltrated  the  water  contour infiltrated  2  plots,  (defined i n section o f sandy loam s o i l . a  to depth  very D  2  small at  volume i n c r e a s e d w i t h t h e i n c r e a s e  30  3.7.3) As i s  amount °C  of  and t h e  i n temperature.  The w e t t i n g f r o n t s w e r e a b o u t 23 p e r c e n t f o r 30° a n d 3 5 °C, a n d about the  24 p e r c e n t f o r 40 °C.  The a p p r o x i m a t e a v e r a g e w i d t h s o f  w e t t i n g f r o n t s w e r e 10, 38 a n d 100 c e n t i m e t e r s f o r 3 0 ° , 35°,  a n d 40 °C r e s p e c t i v e l y . depth  The r a t i o s b e t w e e n a v e r a g e w i d t h s a n d  (15cm) w e r e 0.7 a t 3 0 °C, 2.5 a t 3 5 °C, a n d 6.7 a t 40 °C.  F i g u r e 4.16  V o l u m e t r i c M o i s t u r e Content (%) D i s t r i b u t i o n i n Sandy Loam S o i l i n Layer D2 (15-30cm) under S u r f a c e I r r i g a t i o n .  T h e r e was  no  a t 30° a n d wetting  significant  35  front  °C  movement o f a p p l i e d w a t e r  ( f i g u r e 4.17),  i n case  of  40  °C was  a v e r a g e w i d t h t o d e p t h r a t i o was 40 °C was reach  while  4.  the average width about  60  Figure  4.19  (figure  4  shows  of  centimeters  For depth D  that  surface  irrigation  the wetting  a n d w i d e r a t 40 reasons  could  be  the v e r t i c a l  system.  l o c a t i o n s of  d i f f u s i v i t y at higher  D, 3  the  wetting under  From t h e f i g u r e i t i s o b v i o u s  c o m p a r e d t o 30 a n d  greater  the  4.18).  f r o n t s moved v e r t i c a l l y °C as  3  front could  f r o n t s i n s a n d y loam s o i l a t 30, 35, and 40 °C t e m p e r a t u r e s the  D  and  as i n d e p t h  4  the only temperature at which the w e t t i n g  the depth D  to depth  and 35  conductivity,  laterally °C.  The  deeper  possible  permeability,  t e m p e r a t u r e as d i s c u s s e d  earlier.  and  F i g u r e 4.17  V o l u m e t r i c M o i s t u r e Content (%) D i s t r i b u t i o n i n Sandy Loam S o i l i n Layer D3 (30-45cm) under S u r f a c e I r r i g a t i o n .  F i g u r e 4.18  V o l u m e t r i c M o i s t u r e Content (%) D i s t r i b u t i o n i n Sandy Loam S o i l i n Layer D4 (45-60cm) under S u r f a c e I r r i g a t i o n .  30 Degree C e l s i u s 35 Degree C e l s i u s '40 Degree C e l s i u s iO  0  -25  25  5  D!(0-15cm)  ^ si  ^  ^  ^  D (15-30cm) 2  —*  4  * » ^  •s  \  D (30-45cm  S  3  s  / s  y *  \ / '  t*  ^ * *  s ^  D  4  (45-60cm)  L a t e r a l D i s t a n c e from I r r i g a t i o n S o u r c e  4.19  *  *  * s  \  Figure  Z*-"  (cm)  Wetting Front Locations at Different Locations for Sandy Loam Soil under Surface I r r i g a t i o n System.  4.4.4.1.2  S i l t Loam Soil  In the s i l t  loam s o i l ,  was p o n d e d o n s o i l loam  soil,  s u r f a c e w e r e much l o n g e r t h a n  3 2 1 , 2 2 0 , a n d 178 m i n u t e s  respectively. moisture  the durations the i r r i g a t i o n  F o r depth  water  f o r t h e sandy  a t 30°, 35°, a n d 40 °C,  D i , t h e maximum  percent  volumetric  c o n t e n t s w e r e b e l o w t h e p o i n t o f a p p l i c a t i o n a t 3 0° a n d  35 °C, b u t i t moved away t o w a r d s e a s t a n d w e s t o f t h e s o u r c e a t 40 °C.  From f i g u r e  irrigation  source,  4.20, w i t h i n  25 c e n t i m e t e r  the volumetric  r a n g e d f r o m 54-50 a n d 53-52 p e r c e n t ; radii,  observed  content  When t h e t e m p e r a t u r e  (some s m a l l , some r e l a t i v e l y irrigation.  The s h i f t  from t h e  content  a n d f r o m 25-50  i t r a n g e d f r o m 50-49 a n d 51-47 p e r c e n t ,  respectively.  before  moisture  radii  percent  centimeter  a t 30° a n d 35 °C,  was 40 °C, f e w c r a c k s l a r g e ) on t h e s o i l  o f maximum v o l u m e t r i c  were  surface moisture  f r o m t h e c e n t e r o f p l o t may b e due t o t h e o c c u r r e n c e o f  preferential  flow.  For depth  D, 2  t h e maximum p e r c e n t  moisture  c o n t e n t was b e l o w t h e p o i n t o f a p p l i c a t i o n a t 3 0 °C b u t t h a t was not  t h e case  f o r 35° a n d 40 °C a s shown  volumetric moisture at  different  4.21.  The  c o n t e n t d i s t r i b u t i o n p a t t e r n s were d i f f e r e n t  temperatures  again  f o r the possible  flow induced by cracks i n the s o i l p r o f i l e 3 0 °C, t h e v o l u m e t r i c w a t e r c o n t e n t percent  i n figure  w i t h i n 25 c e n t i m e t e r  preferential  a t 35° a n d 40 °C.  percent  ranged  from  At  48-45  r a d i u s a n d f r o m 45-44 p e r c e n t f o r  t h e 25-50 c e n t i m e t e r r a d i u s f r o m t h e i r r i g a t i o n  source.  F i g u r e 4.20  V o l u m e t r i c Moisture Content (%) D i s t r i b u t i o n i n S i l t Loam S o i l i n Layer DI (0-15cm) under Surface I r r i g a t i o n System.  Figure 4.21  Volumetric Moisture Content (%) D i s t r i b u t i o n i n S i l t Loam S o i l i n Layer D2 (15-30) under Surface I r r i g a t i o n System.  The d i s t r i b u t i o n p a t t e r n o f s o i l 35  °C r e v e a l e d  located  that  below  t h e maximum p e r c e n t m o i s t u r e c o n t e n t  the water  east from the source centimeter radius  water content percent a t  source but a l i t t l e  ( f i g u r e 4.21).  toward  was  the south  The c o n t o u r s w i t h i n t h e 25  from the i r r i g a t i o n water source ranged  from  47-42 p e r c e n t w h i l e w i t h i n t h e 25-50 c e n t i m e t e r r a d i u s f r o m t h e i r r i g a t i o n w a t e r s o u r c e r a n g e d f r o m 45-42 p e r c e n t . the  maximum  percent  volumetric  moisture  content  F o r 40 °C, was  located  towards t h e west of t h e water a p p l i c a t i o n p o i n t and t h e m o i s t u r e content  percent  centimeter radius D  3  ranged  radius  47-41  a n d 47-36 p e r c e n t  from the water source.  percent  with  the  25  f o r t h e 25-50 c e n t i m e t e r  The w e t t i n g f r o n t i n s o i l  depth  ( f i g u r e 4.22) was a n e l o n g a t e d c i r c l e e x t e n d i n g 3 0 c e n t i m e t e r  east and west, center  a t 30  irregular  and about °C.  At  circular  the higher  shapes  followed  the  °C,  about  60  s o u t h from t h e  the wetting and  90  fronts  had  centimeter  in  Once a g a i n t h e w e t t i n g f r o n t was b i g g e r  temperature  s m a l l e r a t t h e 30 °C. front  3 0 c e n t i m e t e r towards  35° a n d 40  diameter, r e s p e c t i v e l y . at  between  (40 °C) ,  The d e p t h D same  trend  4  as  second  was  a t 35  ( f i g u r e 4.23), in  depth  °C  and  the wetting  D, 3  with  the  a p p r o x i m a t e d i a m e t e r s o f 60, 65, a n d 75 c e n t i m e t e r s a t 30°, 35°, a n d 40 °C, r e s p e c t i v e l y . The v e r t i c a l  locations of the wetting fronts a t d i f f e r e n t  t e m p e r a t u r e s show d e e p e r movement o f t h e i r r i g a t i o n w a t e r the  r o o t zone  ( f i g u r e 4.24) a s c o m p a r e d t o t h e s a n d y l o a m  into soil.  Figure 4.22  Volumetric Moisture Content (I) D i s t r i b u t i o n i n S i l t Loam S o i l i n Layer D3 (30-45cm) under Surface I r r i g a t i o n System.  Figure 4.23  Volumetric Moisture Content (%) D i s t r i b u t i o n i n S i l t Loam S o i l i n Layer D4 (45-60cm) under Surface I r r i g a t i o n System.  •30 Degree C e l s i u s 35 Degree C e l s i u s •40 Degree C e l s i u s -ISO  -25  0  25  50  Di(0-15cm)  D (15-30cm) 2  u  a  a •H  o  L a t e r a l D i s t a n c e s from I r r i g a t i o n S o u r c e (cm)  Figure  4.24  Wetting Front Locations at Different Locations for Silt Loam Soil under Surface I r r i g a t i o n System.  Soil soils on  texture  like silt  the s o i l  loam s o i l ,  water  capillary  forces.  water  the s o i l  on  significant there  p r o b a b l y has a r o l e  i n fine-textured  g r a v i t y f o r c e s have a l i m i t e d  movement  as t h e f l o w  But i n t h i s surface,  case,  i s dominated  since  the g r a v i t y  there  forces  was more l a t e r a l  as w e l l  as v e r t i c a l  loam s o i l .  c a p i l l a r y forces had a l i m i t e d  and g r a v i t y dominated t h e f l o w .  effect by the  was may  r o l e i n addition to the c a p i l l a r y forces,  f r o n t s i n t h e case of s i l t the  since  ponded have  a  therefore  spread of  wetting  W h i l e i n sandy loam  soil,  e f f e c t on t h e w a t e r movement  4.4.4.2  Trickle Irrigation  Under t r i c k l e i r r i g a t i o n , volume  takes  depending  circular,  on s o i l  t h e geometry o f t h e w e t t e d  spherical  type,  when  or ellipsoidal  water  i s applied  like from  soil  shapes a point  source.  4.4.4.2.1 Sandy Loam  Soil  F i g u r e 4 . 2 5 Shows t h e d i m e n s i o n s in  t h e t o p 15 c e n t i m e t e r d e p t h  3 0°,  35°,  a n d 40 °C.  of the wetted s o i l  volume  (Di) o f t h e s a n d y l o a m s o i l a t  The b o u n d a r i e s  of the wetted  soil  volume  (wetting fronts) a r e reasonably w e l l d e f i n e d and a r e surrounded by d r i e r  soil.  volumetric  I t c a n be n o t e d from t h e c o n t o u r p l o t s t h a t t h e  soil  water  content  distribution  within  the wetter  volumes a r e n o t u n i f o r m , i t decreased w i t h t h e r a d i a l from  the i r r i g a t i o n  water  source.  distance  A close observation of the  w e t t i n g f r o n t s , showed t h a t t h e t e m p e r a t u r e h a d a n e f f e c t o n i t s horizontal  location  from  the water  source  s u r f a c e w e t t e d p a t t e r n s were symmetric, moisture  content  temperatures. the  25  emitter,  22%,  were  below  and from  25-50  ranged between 36-32%,  Di f o r  content percent  centimeter  36-28%,  The  a n d t h e maximum p e r c e n t  the e m i t t e r i n depth  The v o l u m e t r i c m o i s t u r e  centimeter  (emitter).  36-25%,  radii  within  from t h e  and 32-23%,  2 5 - 2 1 % a t 3 0 ° , 3 5 ° , a n d 40 °C, r e s p e c t i v e l y .  a l l  25-  Figure 4.25  Volumetric Moisture Content (%) D i s t r i b u t i o n i n Sandy Loam S o i l i n Layer DI (0-15cm) under T r i c k l e I r r i g a t i o n System.  For  depth  symmetric  D, 2  while  the wetting  i t was  fronts  asymmetric  a t 3 0°  at 35  a n d 40  °C w e r e  °C, b u t t h e maximum  p e r c e n t m o i s t u r e c o n t e n t s were s t i l l b e l o w t h e t r i c k l e s o u r c e a t all  temperatures  fronts were  (figure  4.26).  The e x t e n t s o f t h e w e t t i n g  were r e d u c e d as compared t o d e p t h Di and t h e l o c a t i o n s about  t h e same  wetting fronts  f o r a l l temperatures.  i n case of depth D , 3  The  extents of  f u r t h e r r e d u c e d f o r 3 0° a n d  35 °C b u t r e m a i n e d a b o u t t h e same f o r 40 °C a s c o m p a r e d t o d e p t h D  2  ( f i g u r e 4.27).  The p o s s i b l e r e a s o n f o r t h e above m i g h t be t h e  movement o f more w a t e r t o a d e e p e r l a y e r a t h i g h e r t e m p e r a t u r e . The  l o c a t i o n of wetting fronts  i n the r a d i i  o f 20, 30, a n d 35 c e n t i m e t e r s f o r 30°, 35°, a n d 40  °C, r e s p e c t i v e l y . radii  from t h e i r r i g a t i o n s o u r c e were  The v o l u m e t r i c m o i s t u r e c o n t e n t p e r c e n t i n t h e  o f 25 a n d f r o m  25-50  c e n t i m e t e r from  the point  source  r a n g e d f r o m 29-25%, 33-27%, 34-28%, a n d 25-24%, 27-24%, 2 8 - 2 5 % , a t 30°, 35°, a n d 40 °C, r e s p e c t i v e l y . 4.28), at  the s o i l  I n case o f depth D  m o i s t u r e d i s t r i b u t i o n p a t t e r n s were  a l l temperatures, and t h e l o c a t i o n  4  (figure  asymmetric  o f t h e maximum  percent  v o l u m e t r i c m o i s t u r e c o n t e n t was b e l o w t h e e m i t t e r i n t h e c a s e s of  3 0° a n d 40 °C a n d away f r o m t h e c e n t e r i n t h e c a s e o f 3 5 °C.  The  g e o m e t r i c shapes  were e l l i p s o i d a l c a s e o f 40 °C. °C w e r e a b o u t 40 °C a b o u t  of the wetting  f r o n t s w i t h 30° a n d 3 5 °C  shaped and an i r r e g u l a r c i r c u l a r shaped i n t h e  The d i a m e t e r s o f t h e w e t t i n g f r o n t s a t 3 0° a n d 35 t h e same b u t s i g n i f i c a n t l y b i g g e r i n t h e c a s e o f  50 c e n t i m e t e r s .  30 Degree Celsius  35 Degree Celsius  40 Degree Celsius  Figure 4.26 Volumetric Moisture Content (I) D i s t r i b u t i o n i n Sandy Loam S o i l i n Layer D2 (15-30cm) under T r i c k l e I r r i g a t i o n System.  30 Degree Celsius  35 Degree Celsius  40 Degree Celsius  Figure 4.27 Volumetric Moisture Content (%) D i s t r i b u t i o n i n Sandy Loam S o i l i n Layer D3 (30-45cm) under T r i c k l e I r r i g a t i o n System.  30 Degree Celsius  Figure 4.28  35 Degree Celsius  40 Degree Celsius  Volumetric Moisture Content (%) D i s t r i b u t i o n i n Sandy Loam S o i l i n Layer D4 (45-60cm) under T r i c k l e I r r i g a t i o n System.  F i g u r e 4.29 the  wetting  significant and  35  shows t h e v e r t i c a l a n d h o r i z o n t a l  fronts. difference  °C, w h i l e  It  can  be  noted  that  between the w e t t i n g  front  the temperature  affect  on  locations there  was  of no  location at 3 0  the wetting  l o c a t i o n a t 40 °C a s c o m p a r e d t o 30 a n d 35 °C i s o b v i o u s .  front  30 Degree 35 Degree '40 Degree  Celsius Celsius Celsius  L a t e r a l D i s t a n c e from I r r i g a t i o n S o u r c e  Figure  4.29  (cm)  Wetting Front Locations at Different Locations for Sandy Loam Soil under Trickle I r r i g a t i o n System.  4.4.4.2.2 In  Silt  Loam  t h e case  Soil  of s i l t  loam  soil,  t h e maximum p e r c e n t  water  c o n t e n t i n t h e t o p 15 c e n t i m e t e r l a y e r  below  the t r i c k l e  irrigation  Di were  volumetric  from t h e p o i n t radii  moisture content i n the r a d i i s o u r c e w e r e 54-53%,  Soil  f o r 3 5° a n d 40 °C,  b u t s y m m e t r i c f o r t h e 30 °C, a s shown i n f i g u r e 4.30. of  located  source a t a l l temperatures.  w a t e r d i s t r i b u t i o n p a t t e r n s were asymmetric  The r a n g e s  of 25 centimeter  52.50-51%,  51-46%; a n d f o r  o f 25-50 c e n t i m e t e r f r o m t h e e m i t t e r r a n g e d  from  53-50%,  51-48%, a n d 46-44%, a t 30°, 35°, a n d 40 °C, r e s p e c t i v e l y . as  i n previous experiments,  the volumetric  moisture  Again content  ranges were h i g h e r a t l o w e r t e m p e r a t u r e i n t h e t o p l a y e r and d e c r e a s e d as temperature i n c r e a s e d . soil,  for  a t a l l temperatures.  silt  loam  soil  smaller pore s i z e s r e s u l t i n g  Silt  i n more l a t e r a l  w a t e r o c c u r r e d due t o t h e c a p i l l a r y a c t i o n .  loam  i nthe case soil  the irrigation  source, but the s o i l  I n depth D , again 2  boxes  water  f o r a l l temperatures.  boundaries of thewetting  fronts  has a  spread of applied  maximum v o l u m e t r i c m o i s t u r e c o n t e n t s i n p e r c e n t w e r e  p a t t e r n s were asymmetric the  loam  where t h e e x t e n t o f t h e w e t t i n g f r o n t s d i d n o t r e a c h t h e i t d i d r e a c h t h e s i d e s o f boxes  below  (Di) ,  U n l i k e t h e sandy  w a l l s o f t h e boxes,  the  soil  distribution  As i n d e p t h D i ,  reached t h e sides  a t 35° a n d 40 °C, b u t n o t f o r 30 °C ( f i g u r e  found  4.31).  of the  30 Degree C e l s i u s  35 Degree C e l s i u s  40 Degree Celsius  Figure 4.30 Volumetric Moisture Content (%) D i s t r i b u t i o n i n S i l t Loam S o i l i n Layer DI (0-15cm) under T r i c k l e I r r i g a t i o n System.  Figure 4.31  Volumetric Moisture Content (%) D i s t r i b u t i o n i n S i l t Loam S o i l i n Layer D2 (15-30cm) under T r i c k l e I r r i g a t i o n System.  In  the r a d i i  of  25  centimeter  from  v o l u m e t r i c m o i s t u r e c o n t e n t p e r c e n t were 50.5-48%;  a n d f r o m 25-50 c e n t i m e t e r r a d i i ,  the emitter,  from  50-46%,  the  49-47%,  i t ranged  from 46-  4 1 % , 47-44%, 47-46%, a t 30°, 35°, a n d 40 °C, r e s p e c t i v e l y . d e p t h D , t h e p a t t e r n s o f s o i l w a t e r d i s t r i b u t i o n were  For  asymmetric  3  f o r 3 5° a n d 40 °C a n d j u s t a b o u t s y m m e t r i c f o r 3 0 °C, a s shown i n the  figure  defined  4.32.  The b o u n d a r i e s  of wetting  f o r a l l the temperatures,  and as  fronts  are well  i n the previous  e x p e r i m e n t s , t h e maximum p e r c e n t m o i s t u r e c o n t e n t s w e r e below  the source  of i r r i g a t i o n  water.  located  The v o l u m e t r i c  m o i s t u r e c o n t e n t p e r c e n t w i t h i n t h e 25 c e n t i m e t e r r a d i i  from t h e  p o i n t s o u r c e w e r e 50-48.5%, 49-48%, a n d 50.5-48%, w h i l e the r a d i i  o f 25-50 c e n t i m e t e r f r o m t h e i r r i g a t i o n  soil  within  source, the  w a t e r c o n t e n t p e r c e n t r a n g e d f r o m 48.5-46%, 48-44%, a n d 4 8 - 4 5 % , a t 300, 350, a n d 40 °C, r e s p e c t i v e l y . d i s t r i b u t i o n patterns f o r a l l  Once a g a i n , t h e s o i l  t h e t e m p e r a t u r e s were  water  asymmetric.  The l o c a t i o n o f maximum p e r c e n t v o l u m e t r i c m o i s t u r e c o n t e n t i n depth  D  4  (figure  were 4.33).  n o t found I n case  below  the water  application  o f 35 °C, t h e maximum p e r c e n t  source water  c o n t e n t was f o u n d a b o u t 25 c e n t i m e t e r t o w a r d s t h e s o u t h f r o m t h e emitter,  a n d f o r 30° a n d 40 °C, i t was s l i g h t l y  t r i c k l e source.  south of the  The 40 °C w e t t i n g f r o n t ' s s p r e a d was t h e l a r g e s t  a n d i t was a b o u t t h e same f o r 30° a n d 35 °C t e m p e r a t u r e s .  30 Degree Celsius  (cm)  Figure 4.32  35 Degree Celsius  40 Degree Celsius  (cm)  (cm)  Volumetric Moisture Content (I) D i s t r i b u t i o n i n S i l t Loam S o i l i n Layer D3 (30-45cm) under T r i c k l e I r r i g a t i o n System.  Figure 4.33  Volumetric Moisture Content (I) D i s t r i b u t i o n of S i l t Loam S o i l i n Layer D4 (45-60cm) under T r i c k l e I r r i g a t i o n System.  The l a t e r a l different differences soil  temperatures are  l o c a t i o n s i n the s i l t shown  between the w e t t i n g  and s i l t  wetting  and v e r t i c a l  fronts  i n figure  front  4.34.  locations  loam s o i l were t h e g r e a t e r l a t e r a l i n the s i l t  loam  soil.  loam s o i l The  i n sandy  at  major loam  spreads of the  30 D e g r e e C e l s i u s 35 D e g r e e C e l s i u s '40 D e g r e e C e l s i u s -!iO  -25  0  25  5  Soil Depth (cm)  (0-15cm)  2  (15-30cm)  3  (30-45cm)  D k A  \ \  \\  D  /J  /' •  (45-60cm) \  L a t e r a l D i s t a n c e from  Figure  I r r i g a t i o n S o u r c e (cm)  4.34 Wetting Front Locations at Different Locations for Silt Loam Soil under Trickle Irrigation System.  CHAPTER V SUMMARY AND CONCLUSIONS  5.1  Summary S t u d i e s t o determine water d i s t r i b u t i o n p a t t e r n s i n sandy  loam  and s i l t  systems  at  soils  different  laboratories Department.  loam  of  under  surface and m i c r o - i r r i g a t i o n  temperatures  t h e Chemical  were  and  conducted  Biological  i n the  Engineering  The c o n d i t i o n s were s i m u l a t e d a s i f a n o n i o n c r o p  were grown i n t h e B a l o c h i s t a n P r o v i n c e o f P a k i s t a n . Wooden b o x e s w e r e u s e d f o r t h i s e x p e r i m e n t . depth  of onion  Bliesner,  a t m a t u r i t y ranges  from  3 0-60  The r o o t i n g cm  ( K e l l e r and  1 9 9 0 ) , b a s e d o n t h e s e s t u d i e s 1 5 cm v e r t i c a l  segments  were s e l e c t e d t o r e p r e s e n t d i f f e r e n t segments o f t h e o n i o n r o o t zone. S o i l p r o p e r t i e s such as b u l k d e n s i t y ,  field  capacity, and  v o l u m e t r i c w a t e r c o n t e n t were d e t e r m i n e d i n o r d e r t o c a l c u l a t e the  t o t a l volume o f w a t e r and f l o w r a t e t o be a p p l i e d . For  t h e sandy  loam  soil,  the pre-irrigation volumetric  m o i s t u r e c o n t e n t was 1 9 % , a n d f o r s i l t (approximately  75% of  field  loam  capacities).  soil,  i t was 3 7 % This  initial  v o l u m e t r i c m o i s t u r e c o n t e n t was b a s e d o n t h e Management A l l o w e d  Depletion of  field For  (MAD) l e v e l o f s o i l w a t e r f o r o n i o n c r o p w h i c h i s 2 5 % capacity  (ASCE,  1990).  s u r f a c e i r r i g a t i o n , w a t e r was a p p l i e d f r o m a t a p i n t h e  l a b o r a t o r y t h r o u g h a p l a s t i c hose the  box.  silt  P r e s s u r e Compensating  loam s o i l  ( s i p h o n tube) a t t h e c e n t e r o f  E m i t t e r s o f 7.6 LPH (2 GHP) f o r  a n d 19 LPH (5 GPH) f o r s a n d y l o a m s o i l w e r e u s e d  f r o m t h e same t a p f o r d r i p i r r i g a t i o n .  P r e s s u r e was  regulated  w i t h a p r e s s u r e r e g u l a t o r a n d was k e p t a t a b o u t 83 k P a (12 p s i ) during a l l runs.  The e m i t t e r s w e r e c a l i b r a t e d a n d . t h e  results  showed t h a t t h e a c t u a l d i s c h a r g e o f 7.6 LPH one was 6.8 LPH a n d the  19 LPH one was a c c u r a t e .  A p p l i c a t i o n t i m e f o r e a c h r u n was  b a s e d on t h e c a l i b r a t e d d i s c h a r g e r a t e s o f t h e e m i t t e r s . A r t i f i c i a l h e a t lamps were u s e d a n d t h e h e a t f r o m t h e lamps was c o n t r o l l e d w i t h dimmers a t t a c h e d t o t h e l a m p s . was m e a s u r e d a n d m o n i t o r e d w i t h surface.  4 thermometers  points  a t the s o i l  Soil  depths  0-2, 5, 10, 15, 20 a n d >20  application  of  temperature. soil  i n soil  irrigation  Under s u r f a c e  c e n t i m e t e r s from  water  at  irrigation,  different the rate  temperature a t h i g h e r temperature  pronounced  the s o i l showed  temperature b e f o r e and a f t e r t h e  temperature b e f o r e and a f t e r i r r i g a t i o n  soil  different  Both the s o i l s  than a t lower temperature.  operating  o f change i n  i n sandy loam  e x h i b i t e d a s i m i l a r p a t t e r n up t o 15 cm d e p t h . in  at 4  t e m p e r a t u r e was m e a s u r e d a t  s u r f a c e b e f o r e and a f t e r each i r r i g a t i o n . d i s t i n g u i s h a b l e changes  Temperature  soil  A l s o t h e change  (40 °C) i s much more  B e y o n d 15 cm t h e r e was no  s i g n i f i c a n t change i n s o i l irrigation.  temperature p r i o r t o o r a f t e r s u r f a c e  F o r t h e same i r r i g a t i o n m e t h o d t h e c h a n g e s i n s o i l  temperature along the s o i l and a f t e r the cm  soil  irrigation,  especially  temperature i n the s i l t  a t lower  application the  loam were d i f f e r e n t  a t 40 °C.  of i r r i g a t i o n water.  p a t t e r n was a l i t t l e  before  U n l i k e sandy  loam,  loam s o i l was c o n s t a n t b e l o w  o p e r a t i n g temperature  (30 a n d 3 5  the i r r i g a t i o n  a t higher temperatures  changes i n s o i l  10  °C) b e f o r e t h e  However, a f t e r  different  a n d 40 °C) w i t h p r o n o u n c e d soil  for silt  (35  temperature along the  d e p t h up t o 15 cm. With t r i c k l e i r r i g a t i o n ,  s a n d y loam s o i l  difference  i n the s o i l  irrigation  a t 40 °C, h o w e v e r  along s o i l  depth a t lower temperatures  similar  pattern  surface  irrigation,  almost  unchanged  before  temperature p r o f i l e  and a f t e r  the s o i l  both  t h e changes  showed s i g n i f i c a n t prior  i n soil  irrigation.  and a f t e r  temperature  Likewise 15 cm  trickle  Nonetheless, contrary to surface i r r i g a t i o n ,  irrigation,  p r o b a b l y due t o w a t e r  irrigation.  a t 40 °C, t h e s o i l  accumulation  t h i s r e g i o n as a r e s u l t o f s l o w w a t e r a p p l i c a t i o n irrigation.  Silt  loam  temperature p r o f i l e  under  after within  trickle  showed s i g n i f i c a n t c h a n g e s i n s o i l  b e f o r e and a f t e r  operating temperatures. irrigation,  soil  with  remained  t e m p e r a t u r e showed no s i g n i f i c a n t changes up t o 5 cm d e p t h trickle  after  (30 a n d 35 °C) showed a  temperature below  before  t o and  trickle  irrigation  The p a t t e r n was more p r o n o u n c e d  a n d a t b o t h 35 a n d 40 °C, changes i n s o i l  at a l l after  temperature  were  p r o m i n e n t up t o 20 cm d e p t h .  temperature probably under  remained a l m o s t unchanged  due t o w a t e r  trickle  deeper  soil  loam s o i l better  Also  at 35  loam  t e m p e r a t u r e changes  d e p t h s as compared  to surface  soil.  Overall  were o b s e r v e d t o  irrigation  in silt  f o r the p o s s i b l e reason that t r i c k l e i r r i g a t i o n  water  retention  in  soils  soil  up t o 10 cm d e p t h m o s t  retention i n s i l t  irrigation  °C, t h e  as  compared  to  favors surface  irrigation. Under water  e v a p o r a t e d from  standing The  both i r r i g a t i o n  on t h e s o i l  evaporation  under  surface  sandy  loam  t h e volume  and s i l t  of  loam  irrigation  soils  while  s u r f a c e was d e t e r m i n e d b y t h e P a n method.  losses  from  irrigation  ponding duration.  systems,  sandy  mainly  loam  soil  because  The l o s s e s c o r r e c t e d  of  were  negligible  the short  f o r t h e same  water  duration  u n d e r t r i c k l e i r r i g a t i o n w e r e n e g l i g i b l e t o o due t o f a s t e r w a t e r infiltration significant under  irrigation,  But  in silt  both  irrigation  under  into  t h e sandy loam  irrigation  soil  loam  soil.  as compared  systems.  The  losses  t o sandy  However,  loam  under  t h e l o s s e s were 5 - f o l d h i g h e r as compared  irrigation  i n comparison t o surface  i n case  of surface  irrigation,  the surface  soil  surface  to trickle  e v e n t h o u g h t h e d u r a t i o n o f w a t e r p o n d i n g was  trickle  were  longer  irrigation. area  of the  p o n d e d w a t e r was much g r e a t e r a s compared t o t r i c k l e  irrigation,  therefore  soil  more  water  surface i r r i g a t i o n  evaporated from  system.  silt  loam  under  The  soil  measurement  water  was  monitoring/reading layout  at  horizontal  intervals  of  for soil 25  water  centimeters,  s t a r t i n g from t h e p o i n t o f a p p l i c a t i o n and moving outward t o t h e edge o f t h e w e t t e d s u r f a c e .  The r e a d i n g s f o r w a t e r c o n t e n t w e r e  t a k e n a f t e r t h e t e r m i n a t i o n o f i r r i g a t i o n as s o o n as a l l p o n d e d w a t e r was  infiltrated/evaporated,  u s i n g M o i s t u r e Point™  Model  MP-719, a n d M o i s t u r e P o i n t P r o b e Type-K S o i l M o i s t u r e P r o b e  at  an  an  i n c r e m e n t o f 25  cm  horizontally  i n c r e m e n t o f 15 cm v e r t i c a l l y  from the c e n t e r  and  at  from the water s o u r c e i n o r d e r t o  determine the volumetric water content d i s t r i b u t i o n p a t t e r n s i n the  soil  profile  under  investigation.  The  average  t h r e e r e a d i n g s f o r e a c h d e p t h a t e a c h p o i n t was u s e d . h a d f o u r 15 cm l o n g segments w h i c h m e a s u r e d v o l u m e t r i c moisture content i n the s o i l  value The  of  probe  d i r e c t l y the average  layer.  The t i m e domain r e f l e c t o m e t r y t e c h n i q u e was u s e d t o measure the  soil  moisture content.  The  volume  balance approach  adopted to study the s o i l water d i s t r i b u t i o n i n a l l four (Di,  D, 2  D, 3  irrigation  and  D) .  Based  4  volumetric  on  moisture  the p r e - i r r i g a t i o n content  data,  the  and  was  layers post-  change  in  v o l u m e t r i c w a t e r c o n t e n t as a r e s u l t o f added w a t e r was d e t e r m i n e d and p l o t t e d . all  The w a t e r volumes c a l c u l a t e d w i t h t h i s a p p r o a c h f o r  the depths w i t h i n  t h e r o o t z o n e w e r e u s e d t o d e t e r m i n e what  p e r c e n t a g e o f t h e t o t a l amount o f w a t e r a p p l i e d was s t o r e d i n e a c h depth.  The l o w e r t h e t e m p e r a t u r e , t h e h i g h e r t h e volume o f w a t e r  s t o r e d i n the top l a y e r  (Di) a n d t h e p a t t e r n r e v e r s e d i n l o w e r  layers  -  D,  stored  at  The  °C) to  and  3  higher  irrigation  silt  D,  2  D-  temperatures  soil  depth.  higher  volumetric  the top l a y e r  sandy soil  (30  (Di) .  loam and water  and  under  both  profiles  f o r sandy loam  silt  ( 3 0 , 3 5 , and  systems were  developed  content  profiles  represent  35  content °C)  and  percent the  at the h i g h e r  were  lowest  ( 4 0 °C)  temperature  in  layers  (D , 2  d i s c u s s e d i n the previous chapter. soils  trends  under  were  trickle  the  irrigation,  same  as  in  at  loam s o i l had h i g h e r v o l u m e t r i c  - 5 0 and  50 centimeter  from  the  s u c h as s i l t  the  soil  moisture  emitter  content  percent  as  I n g e n e r a l , g r a v i t y f o r c e s have a soils  loam s o i l , where the c a p i l l a r y f o r c e s dominate sandy loam s o i l  In  surface  l i m i t e d e f f e c t on t h e w a t e r movement i n t h e f i n e - t e x t u r a l  s o u r c e due  the  volumetric  t r e n d .reverses i n the lower  compared t o sandy loam s o i l .  moisture  the  at  loam  as s i l t  percent  The  40  However t h e l a t e r a l d i s t r i b u t i o n i n s a n d y l o a m  different,  flow.  and  moisture and  The  profiles  irrigation.  content  were  source.  f o r the reasons  4  water  l a t e r a l l y around the i r r i g a t i o n  content percents  and D )  of  s p a t i a l d i s t r i b u t i o n of a p p l i e d water  Moisture  temperatures  moisture  3  soils  trickle irrigation  volumetric s o i l moisture  D,  f o r both  at three d i f f e r e n t temperatures  i l l u s t r a t e the l a t e r a l  lower  volumes  v o l u m e t r i c water content  u n d e r s u r f a c e and  The  higher  systems.  loam s o i l s  along  was  where  4  had  a r a p i d decrease  laterally  away  from  the  i n volumetric  the  application  to the h i g h e r c o n d u c t i v i t y , w h i l e the s i l t  loam  soil  with  lower  gradual  conductivity  decline  and  higher  capillarity  i n the volumetric  moisture  had  a  content  more  percent  l a t e r a l l y away f r o m t h e p o i n t s o u r c e . An  understanding  of  the  soil  water  distribution  was  developed f o r b o t h s o i l s , under b o t h i r r i g a t i o n techniques a t a l l three  temperatures  using  Graphic  (30°, 35°, a n d 40 °C) .  Software  SURFER  f o r both  Contours soils  were  and  irrigation  methods a n d f o r a l l f o u r d e p t h s u s i n g v o l u m e t r i c m o i s t u r e r e a d i n g s a t d i f f e r e n t p o i n t s and t e m p e r a t u r e s .  drawn  content  I n these contours,  w e t t e d p a t t e r n s w e r e s t u d i e d a n d t h e d i f f e r e n c e s w i t h i n t h e same soil  t y p e , i r r i g a t i o n method a n d d e p t h s a t d i f f e r e n t  were  identified  and d i s c u s s e d .  In the contours,  f r o n t s a r e i d e n t i f i e d by the hatched contours vertical  lines)  f o r both s o i l s  temperatures the wetting  (contours w i t h t i n y  and i r r i g a t i o n t e c h n i q u e s i n a l l  f o u r d e p t h s a t 30, 35, a n d 40 °C t e m p e r a t u r e s . The w e t t i n g f r o n t , which  i s indicative  of the l o c a t i o n  where  moisture  the i n i t i a l  moisture  content  equals  content  ( b e f o r e i r r i g a t i o n ) has been used t o d e s c r i b e t h e e x t e n t  of  the s o i l  different content  a b o u t 2 p e r c e n t more t h a n  the s o i l  volumetric  conditions.  after  moisture  content  distribution  under  The maximum p e r c e n t v o l u m e t r i c m o i s t u r e  irrigation  was  found  source i n the m a j o r i t y of experiments  just  below  the  f o r both s o i l s .  irrigation But the  i r r i g a t i o n s o u r c e d i d n o t behave as i d e a l i z e d p o i n t s o u r c e though  i t was  volumetric  close  moisture  i n the majority content  of  percentages  experiments. were  different  even The at  different  depths  application, water The  maximum r a n g e more  t h e same  radii  from  the point  p r o b a b l y due t o t h e e f f e c t o f t e m p e r a t u r e  viscosity,  that  within  water  temperatures  s u r f a c e t e n s i o n and h y d r a u l i c  into  deeper  than a t lower temperature.  on  soil  conductivity.  a t 3 0 °C a n d t h e minimum a t 40 °C, infiltrated  of  layers  Lateral  indicated at  higher  and  vertical  movements o f a p p l i e d w a t e r w e r e g r e a t e r a t 35° a n d 40 °C t h a n a t 3 0 °C a n d t h e l o w e r v o l u m e t r i c m o i s t u r e c o n t e n t r a n g e s a t 3 5° a n d 40 °C i n t h e t o p 15 cm l a y e r i n d i c a t e d t h a t t h e v e r t i c a l of  a p p l i e d w a t e r was a l s o g r e a t e r a t t h o s e t e m p e r a t u r e s .  small  amounts  depths  of  a t 30 °C.  irrigation  wetting both  front  soils  increased  and under  f r o n t s moved v e r t i c a l l y °C t h e n  greater  at 30  water  infiltrated  The i n f i l t r a t e d v o l u m e  i n c r e a s e d w i t h an i n c r e a s e  40  movement  both  lower depths  The s p r e a d o f t h e i n temperature f o r  methods.  The w e t t i n g  a n d l a t e r a l l y more d e e p l y a n d w i d e l y a t  and 3 5  conductivity,  the increase irrigation  the  i n the lower  i n temperature.  with  to  Very  °C.  The p o s s i b l e  permeability,  t e m p e r a t u r e as d i s c u s s e d i n e a r l i e r  reasons  and d i f f u s i v i t y sections.  could  be  at higher  5.2  Conclusions The  following  conclusions  d i s t r i b u t i o n patterns  i n soil  s u r f a c e and m i c r o - i r r i g a t i o n  1)  drawn  at different  from  the  water  temperatures,  under  systems:  The r e s u l t s o f t h i s s t u d y c l e a r l y show t h a t t h e t e m p e r a t u r e has  a  significant  effect  on  soil  water  distribution  patterns  and on t h e shape and volume o f t h e w e t t e d  profile,  which i s of p a r t i c u l a r  field  2)  were  irrigation  Temperature hydraulic  interest  soil  i n the design of  systems.  must be g i v e n more a t t e n t i o n a s o t h e r s o i l a n d parameters  i n the design of both  surface  and  m i c r o - i r r i g a t i o n methods.  3)  Considering the r e s u l t s designs  and  temperature hydraulic  of this  management regime  properties  should  (climate) and  study, i r r i g a t i o n  to  be  adjusted  i n addition the  water  to and  system to  the  the  soil  nutrients  requirements of the s p e c i f i c crop.  4)  The d i s t i n c t p a t t e r n s o f s o i l m o i s t u r e d i s t r i b u t i o n the  same i r r i g a t i o n s y s t e m s a n d s o i l  different response,  t y p e s , as a f f e c t e d by  t e m p e r a t u r e s may h a v e a m a r k e d e f f e c t root  growth,  and  water  within  uptake,  on p l a n t therefore,  knowledge  of the e f f e c t  o f t e m p e r a t u r e on  the s o i l  water  d i s t r i b u t i o n i n t h e r o o t zone i s i m p o r t a n t .  5)  The  storage of water  lower  top  15  centimeter layer  t e m p e r a t u r e s a n d more w a t e r movement t o t h e  layers  at  higher  implications water  i n the  the  temperatures  could  irrigation  frequency  f o r the  crop  and  on  choosing  the  have  deeper  profound  i . e . , when  crop  at  type  to  (shallow  r o o t e d o r deep r o o t e d ) .  6)  More w a t e r was the  a p p l i e d to the s i l t  loam s o i l  sandy loam s o i l by the time t h e w e t t i n g f r o n t s  certain  depths,  which  explains  why  volumetric  contents i n percent are h i g h e r i n the s i l t in  7)  as c o m p a r e d t o  t h e sandy loam  The  loam s o i l  of  the  wetting  patterns  d i s t r i b u t i o n i n the s o i l p r o f i l e at d i f f e r e n t surface  that  shallow  and  trickle  rooted  and  irrigation widely  spaced  temperatures.  crops  are  more  and  than  spaced  water  temperatures  methods,  recommended a t l o w e r t e m p e r a t u r e s ; w h i l e closely  moisture  soil.  characteristics  under  reached  indicated  crops  may  deep r o o t e d  suitable  for  be and  higher  8)  The w e t t i n g p a t t e r n s a n d s o i l w a t e r g e o m e t r y the  need  spacing  f o r adjustment  as a f f e c t e d  by the s o i l  addition to the s o i l case  of lower  temperatures  i n the emitters  texture.  temperatures because  of  also  indicated  and  laterals  and a i r temperature i n  Wider s p a c i n g i s b e s t i n t h e and c l o s e r  more  spacing at higher  vertical  than  horizontal  movement o f i r r i g a t i o n w a t e r i n t h e s o i l .  9)  As i n t h e r e s u l t s o f t h i s  s t u d y , t h e deep w e t t i n g  pattern  would expect t h e r o o t s t o p e n e t r a t e deeper i n t o t h e s o i l as a  result  o f t h e movement o f a p p l i e d  layers of root  10)  water  t o t h e deeper  zone.  TDR c a n be u s e d s u c c e s s f u l l y t o d e t e r m i n e w e t t i n g to the  patterns  improve i r r i g a t i o n s c h e d u l i n g , and adapt t h e s c h e d u l e t o system i n use.  I n t h i s s t u d y , TDR c l e a r l y compared t h e  w e t t i n g p a t t e r n s g e n e r a t e d b y two i r r i g a t i o n s y s t e m s i n two s o i l s a t d i f f e r e n t temperatures.  5.3  Practical  Applications  Quantifying  wetting  patterns  as  c a n be u s e d t o d e v e l o p more e f f i c i e n t would help reducing and h e l p m a i n t a i n  a f f e c t e d by irrigation  temperatures  schedules,  c h a n c e s o f deep p e r c o l a t i o n o r w a t e r  s u i t a b l e moisture  that  deficit  f o r r o o t g r o w t h and n u t r i e n t  uptake. It the  i s p o s s i b l e to p r e d i c t the depth of r o o t p e n e t r a t i o n  extent  of  root  exploration  v a r i o u s d e p t h s i s known. T h i s  i f  the  c o u l d t h e n be  i r r i g a t i o n water a p p l i c a t i o n , f e r t i l i z e r to  the  water  and  soil  n u t r i e n t s present  temperature  used to a d j u s t  input levels  (distribution  and at the  according  patterns  at  d i f f e r e n t t e m p e r a t u r e s ) i n t h e r o o t i n g zone t h a t i s a v a i l a b l e t o the  crop. If  root  low  soil  systems  slowing  root  implications cropping occurs  in  temperature can the  lower  growth  largest encourage  the  0-60  cm  amount  of  root  soil  water  and  important  the r i s k Soil  the  of  which  activity.  conservation and  rooting  this  has  zone  the by  important  I t i s known t h a t u n d e r m o s t  a l l of  layer  e x p l o r a t i o n of  the  development,  almost  r e f l e c t e d i n c r o p w a t e r use i t has  portions  f o r crop production.  conditions, in  and  limit  the  soil  water  recharge  also  coincides  with  the  Any  practice  that  can  i n that  crop y i e l d .  soil On  layer w i l l the other  implications for nitrogen f e r t i l i z e r  be  hand,  management  of n i t r o g e n l o s s through l e a c h i n g .  temperature  a l s o a f f e c t s p l a n t uptake  of n u t r i e n t s .  Some n u t r i e n t s s u c h a s p h o s p h o r u s Plant  roots  them.  growth  be  temperatures  will  nutrients w i l l  within  Knowledge  on c o o l  to  soils,  obtain  uptake of supply i s  by  soil  temperature.  the a c t i v i t y  of  organic  of s o i l  matter  Cool  soil  microorganisms.  to plant  available  be l o w e r . exerts  I t also  processes a  nutrients  be l o w e r , u n l e s s a n u t r i e n t  slow  temperature  activities. physical  i s reduced  affected  t h e breakdown  Soil  t o immobile  i n the s o i l .  P l a n t uptake of t h e mobile n u t r i e n t s such as n i t r o g e n  also  Thus,  close  nutrients w i l l  c l o s e by.  of  soil  a strong  influences  within  restricted  understanding with  grow  Since root  immobile  can  must  move v e r y l i t t l e  and  soil-plant  the rates  the s o i l .  range  of  influence  Most  soil  and  t i m e , as does t h e s o i l - w a t e r s t a t e .  of chemical plants  grow  and best  a i r temperature.  a i r temperature relationships.  on b i o l o g i c a l  is  essential  in  Temperature  changes  I t generally  differs  from l a y e r t o l a y e r a t any g i v e n time. The r e s u l t s o f t h i s s t u d y showed t h a t u n d e r b o t h systems and i n b o t h s o i l s , at  higher temperatures,  irrigation  w a t e r moved t o t h e d e e p e r s o i l which  changed  the s o i l  layers  temperatures,  t h a t i s why t h e t e m p e r a t u r e c h a n g e s w e r e t i l l  greater  compared t o t h e l o w e r t e m p e r a t u r e s .  t e x t u r e must a l s o  have  played  patterns  a  due  conductivities.  role to  The s o i l  i n the differences  the water  holding  i n the  capacities  depths as  temperature and  thermal  5.4  Recommendations f o r the a p p l i c a t i o n o f the r e s u l t s o f t h i s r e s e a r c h study:  Intensive literature during  search before s t a r t i n g  the study and  t h e study r e v e a l e d t h a t a i r and s o i l  temperatures  have n o t s u f f i c i e n t l y been c o n s i d e r e d i n t h e c o n t e x t o f t h e movement a n d t h e d i s t r i b u t i o n p a t t e r n s o f i r r i g a t i o n w a t e r in  the s o i l  Since  profile  the results  (root  zone)  of this  temperature  has  an  distribution  patterns,  as d e s i g n  study  important  clearly effect  parameters.  show on  that the  soil  water  t h e shape and volume o f t h e w e t t e d  s o i l p r o f i l e , i t i s s u g g e s t e d t h a t t h e temperature g i v e n e q u a l importance as g i v e n t o o t h e r s o i l parameters  i n the design  of  both  must b e  and h y d r a u l i c  surface  and  micro-  i r r i g a t i o n methods.  Based on t h e r e s u l t s soil in and  of this  water geometry),  study  (wetting p a t t e r n s and  i t i s suggested that the adjustment  t h e e m i t t e r s and l a t e r a l s  s p a c i n g a f f e c t e d by t h e s o i l  a i r t e m p e r a t u r e must b e made i n a d d i t i o n  texture. closely vertical soil.  Wider spaced spaced  to the s o i l  i n case o f lower temperatures and  at higher  than h o r i z o n t a l  temperatures  because  of  more  movement o f i r r i g a t i o n w a t e r i n  As o b v i o u s f r o m t h e r e s u l t s o f t h i s s t u d y , t h e t e m p e r a t u r e effect  on t h e i r r i g a t i o n  different  soil  considered variety  depths,  while  within  shallow roots  water  distribution  a i r and s o i l  selecting  temperature  the crop  t h e same c r o p b a s e d f o r the e f f i c i e n t  patterns i n  type  and  must be also  on t h e d e e p r o o t s  the or  use of a p p l i e d water and  b e t t e r crop production.  Based on t h e r e s u l t s o f t h i s  research,  i t i s suggested to  recognize the importance of the i r r i g a t i o n water s t o r e d i n the  t o p 15 c e n t i m e t e r l a y e r  (how o f t e n t o i r r i g a t e c r o p ) . the  on t h e i r r i g a t i o n  frequency  The s t o r a g e o f more w a t e r i n  t o p 15 c e n t i m e t e r l a y e r a t l o w e r t e m p e r a t u r e s a n d more  w a t e r movement t o t h e d e e p e r l a y e r s a t h i g h e r t e m p e r a t u r e s could  have  profound  implications  for  the  irrigation  f r e q u e n c y , a n d on c h o o s i n g t h e c r o p t y p e ( s h a l l o w r o o t e d o r deep r o o t e d ) .  As i n t h e r e s u l t s o f t h i s s t u d y , t h e r o o t s w o u l d p e n e t r a t e deeper wetting  into  the s o i l  as  a  result  of  deep  cone-shaped  patterns.  TDR c a n be u s e d s u c c e s s f u l l y t o d e t e r m i n e w e t t i n g to the  patterns  improve i r r i g a t i o n s c h e d u l i n g , and adapt t h e s c h e d u l e t o system i n use.  I n t h i s s t u d y , TDR c l e a r l y compared t h e  w e t t i n g p a t t e r n s g e n e r a t e d b y two i r r i g a t i o n s y s t e m s i n two s o i l s a t d i f f e r e n t temperatures.  5.5  Suggestions  f o r Future Research  T h i s s t u d y was c o n d u c t e d i n t h e l a b o r a t o r y , s i m u l a t i n g t h e field  conditions.  It  d i s t r i b u t i o n patterns systems  i n different  province The  suggested  i n soils climatic  that  effect  of  temperatures  i n soils  investigated by  with  to include plants,  regions  interaction  of  évapotranspiration  field with an  Investigations different  and t r i c k l e  irrigation  conditions. distribution  should  be  further  term r e p r e s e n t i n g situations soil  water  where  moisture role  i n the root  i n the  the and soil  zone.  s h o u l d be made t o d e t e r m i n e t h e e f f e c t s o f  temperatures  of d i f f e r e n t  moisture  important  moisture d i s t r i b u t i o n patterns  water  of the B a l o c h i s t a n  grown  the sink  roots play  on  crops  and  the  under d i f f e r e n t  o f P a k i s t a n be c o n d u c t e d u n d e r f i e l d  patterns  uptake  is  ( c l i m a t e s ) on t h e g r o w t h and  c r o p s grown i n d i f f e r e n t irrigation  systems.  soils  under  yield  surface  BIBLIOGRAPHY Abu-Awwad, A.M. 1999. 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I r r i g S c i . 16: 101-105.  Appendices  Appendix A - l EXPERIMENTAL DESIGN Responses Moisture  content  distribution  i n sandy  within  depths D  and D  (45-60 cm) o f s o i l p r o f i l e  4  x  irrigation  (0-15 cm), D  and c l a y e y  (15-30 cm), D  2  2-  3-  (30-45 cm),  a f t e r surface and micro-  a t 30°, 35°, a n d 40° C.  F a c t o r s t o be V a r i e d 1-  3  soils  I r r i g a t i o n Methods i) surface i r r i g a t i o n ii) micro-irrigation  IM IMi IM  =  2  S o i l Types i ) sandy s o i l i i ) clayey s o i l  ST STi ST  =  2  Temperatures i ) 30°C i i ) 35°C i i i ) 40°C  T Ti T T  =  3  2  2  2  3  Treatment Combinations  =  2 x 2 x 3 =  12  With One R e p l i c a t i o n  =  12 x 2  24  =  Appendix A-2 TREATMENT COMBINATIONS 1) I M x S T i x Ti x R  13)  IMi  x  STi  x  T  x  x  R  2) I M ! x S T i x T  x Ri  14)  IMi  x  STi  x  T  2  x  R  3) I M i x S T i x T x R i  15)  IMi  x  STi  x  T  3  x  R  4) I M x S T x T i x R i  16)  IMi  x  ST  2  x  Tix  R  5) I M i x S T x T  2  x Ri  17)  IMi  x  ST  2  x  T  2  x  R  6) I M : x S T x T  3  x Ri  18)  IMj.  x  ST  2  x  T  3  x  R  19)  I M  x  STx x  T i  x  R  x  STi  x  T  2  x  R  x  ST  X  x  T  3  x  R  x  ST  2  x  T i  x  R  x  ST  2  x  T  2  x  R  x  ST  2  x  T  3  x  R  x  X  2  3  X  2  2  2  7)  IM  2  x STi x T i x R  x  8) I M x S T i x T  2  x Ri  20)  I M  9) I M x S T i x T  3  x Ri  21)  I M  10) I M x S T x T i x R i  22)  IM  11) I M x S T x T  2  x Ri  23)  I M  12) I M x S T x T  3  x Ri  24)  IM  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  

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