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Cowpea yield response under alternative irrigation scheduling techniques using line-source sprinklers Tyem, Mamkur Ndam 1984

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COWPEA  Y I E L D R E S P O N S E UNDER A L T E R N A T I V E TECHNIQUES USING LINE-SOURCE  IRRIGATION SPRINKLERS  SCHEDULING  by  MAMKUR B.Sc,  University  A THESIS THE  SUBMITTED  NDAM  TYEM  of Ibadan,  Nigeria,  IN PARTIAL  REQUIREMENTS  1979  F U L F I L M E N T OF  FOR T H E D E G R E E OF  MASTER OF  SCIENCE  in THE  FACULTY  Department  We  accept to  THE  OF G R A D U A T E  of A g r i c u l t u r a l  this  thesis  Mechanics  as conforming  the requii/fd standard  UNIVERSITY  OF B R I T I S H  October  ©  STUDIES  MAMKUR  COLUMBIA  1984  NDAM T Y E M , 1984  In  presenting  this  requirements  f o r an a d v a n c e d  Columbia,  I  available  for  permission  thesis  agree  for  shall  reference  and  study.  I  extensive  be g r a n t e d  representatives. of t h i s  without  Department  of  my  OCTOBER  copying  by t h e H e a d  thesis written  It for  is  o f my  permission.  1,  1984  Columbia  thesis  gain  of of  the  British  i t  freely  agree  that  for scholarly  Department  understood  financial  make  further  of t h i s  AGRICULTURAL MECHANICS  The U n i v e r s i t y o f B r i t i s h 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5  Date:  at the University  Library  or  allowed  degree  fulfilment  the  may  publication  partial  that  purposes her  in  that  or  by  his  copying  shall  not  or be  i i  Abstract A  portable  designed  to  provide  characteristics cowpea  studies.  Both  on  cowpea  dry  conducted  smaller  single  matter  amounts to  gravimetric efficiency indices number  production complete  water  with  Soil  of  the  methods  and  subsequently  nodes  on a  plant  weekly  irrigation-  Walp.)  production  of  irrigation  scheduling  techniques  investigated  design  in  a  frequently  water  normal  of  field-  interval  was  as  well  evaluated. height,  basis  for  three  as  of  seven  depth  measured  Plant  number  with  irrigation  P and  crop  use  but  application  fertilizer  by  water  variable  experiment.  and  levels  was  operating  effects  irrigating  depletion  monitored were: of  were  block  than  five  water  were  irrigation  system  and  [L.]  interactive  and  stage-of-growth  studied  levels.  and  merits  of  continuous  unguiculata  fertilizer  relative  compared  were  the  randomised  The  as  Vigna  irrigation  distribution  for  (  phosphate  sprinkler  water  suitable  fertilizer  water,  hand-move  water growth  trifoliates  water by use rate and  weeks  following  uptake  indicated  emergence. Statistical positive  analyses  response  water,  most  Water  use  of  noticeably efficiency  frequently-irrigated at that for  the  expense  irrigating both  the  yield  of  crop  yield to  under was  plot(S3)  within  water  the  use  but  P  fertilizer  and  high-frequency to  be  this  yields. the  and  added  observed  depressed  twice and  of  highest  happened It  was  designed  efficiency  to  irrigation schedules.  under  the  most  be  obtained  therefore  concluded  interval  was  considerations.  optimum  The used  line-source  in this  study crop.  of  the  One  Special the  was  lateral  found  the  was that  plot,  but  these  system  that  made  needed was  working  be of  of  uniformity  also,  experimental  satisfactory these  the of  to achieve  frequently  were  to  and  encountered  operation high  system  effects  difficulty  to ensure  care  were  interactive  major  experiment conditions  project  irrigation  uncoupled  test  design  for  factors  with  field on t h e  running  system  under  water  distributiion.  sediment  exclusion  a n d moved  the  special  features  with  i t interesting.  of  calm  the  from  the  wind  from  plot  to  irrigation  i v  Table  Abstract L i s t of T a b l e s L i s t of F i g u r e s Acknowledgement  of  Contents  i i vi vii viii  '.  Chapter I INTRODUCTION 1 . 1 B a c k g r o u n d and Statement 1.2 S t u d y O b j e c t i v e s  of  the  Problem  Chapter II L I T E R A T U R E REVIEW 2.1 E v a p o t r a n s p i r a t i o n , C r o p G r o w t h a n d Y i e l d 2.2 I r r i g a t i o n S c h e d u l i n g 2.3 Water S u p p l y and N u t r i e n t A v a i l a b i l i t y to C r o p s 2.4 S t a t e of Knowledge in I r r i g a t e d Cowpea R e s e a r c h Chapter III M A T E R I A L S AND METHODS E X P E R I M E N T A L METHODS 3.1 I r r i g a t i o n System Design 3.1.1 M a x i m u m C r o p E T E s t i m a t i o n By P a n E v a p o r a t i o n 3.1.2 I r r i g a t i o n System Design Computations 3.1.3 S p r i n k l e r S e l e c t i o n and C o n f i g u r a t i o n 3.1.4 L a t e r a l Design 3.1.5 Mainline Design 3.2 E x p e r i m e n t a l D e s i g n and System L a y o u t 3.2.1 I r r i g a t i o n System C h a r a c t e r i s t i c s 3.2.2 E x p e r i m e n t a l D e s i g n and F i e l d L a y o u t 3.3 A p p l i c a t i o n of T r e a t m e n t s 3.3.1 C r o p E s t a b l i s h m e n t a n d M a i n t e n a n c e . . . .• 3.3.2 I r r i g a t i o n Water T r e a t m e n t s 3.3.3 Phosphorus F e r t i l i z e r Treatments 3.3.4 I r r i g a t i o n Scheduling Techniques  B.  A N A L Y T I C A L PROCEDURES 3.4 The S o i l 3.4.1 Soil Analyses . . . . 3.4.2 S o i l Moisture Determinations During 3.5 The C r o p 3.5.1 Crop Growth I n d i c a t o r s 3.5.2 Crop Y i e l d 3.5.3 N u t r i e n t Uptake 3.5.4 Statistical Comparison of R e s u l t s  DISCUSSION Properties Development Y i e l d Response  9 9 13 ...19 ...26  30  A.  C h a p t e r IV R E S U L T S AND 4.1 Soil 4.2 Crop .4.3 C r o p  1 1 7  Experiment  30 30 ...31 33 34 34 36 36 36 ..37 38 38 42 46 47 51 51 51 ..52 53 53 54 54 55  56 56 59 60  V  4.3.1 E f f e c t o f I r r i g a t i o n on Y i e l d s 66 4.3.2 E f f e c t o f P h o s p h o r u s F e r t i l i z e r on Y i e l d 76 4.3.3 E f f e c t s o f F a c t o r I n t e r a c t i o n s on Cowpea Y i e l d ..77 4.4 E f f e c t o f I r r i g a t i o n on F e r t i l i z e r U t i l i z a t i o n ....82 4.5 Water Use E f f i c i e n c y 91 4.6 C r o p P r o d u c t i o n F u n c t i o n s 95 4.6.1 Y i e l d - W a t e r Model 96 4.6.2 Y i e l d - F e r t i l i z e r F u n c t i o n a l R e l a t i o n s h i p 99 Chapter V SUMMARY AND CONCLUSIONS 5.1 Summary 5 . 2 Conclusion 5.3 R e c o m m e n d a t i o n s f o r F u r t h e r  Studies  LITERATURE CITED  109 109 114 115 118  APPENDIX A - METEOROLOGICAL DATA USED I N IRRIGATION DESIGN 1 26 APPENDIX B - CATCH CAN LAYOUT FOR WATER DISTRIBUTION TEST  1 27  APPENDIX C - PLANT A N A L Y S I S : AUTOANALYSER PLOT  129  APPENDIX D - AUTO ANALYSER N AND P DATA  130  APPENDIX E - SOME GRAVIMETRIC MOISTURE DETERMINATION RESULTS '  131  vi  List  of T a b l e s  I.  Soil  Report of the E x p e r i m e n t a l Area  II.  Computed E v a p o t r a n s p i r a t i o n I n f o r m a t i o n  32  III.  F e r t i l i z e r data  47  IV.  S o i l Analyses Results System  V.  Mean E x t r a c t a b l e  VI.  Results  VII.  Dry M a t t e r Y i e l d ,  VIII.  Analysis  IX.  S x P I n t e r a c t i o n on Cowpea Y i e l d ,  t/ha  72  X.  P x W I n t e r a c t i o n on Cowpea Y i e l d ,  t/ha  72  XI.  Plant Analyses Results  85  XII.  Analysis  87  XIII.  S x P I n t e r a c t i o n on P - U p t a k e , ppm  88  XIV.  P x W I n t e r a c t i o n on P - u p t a k e , ppm  88  XV.  Yield, Evapotranspiration Results  93  XVI.  Comparison of A c t u a l  of S o i l  31  B a s e d on Morgan S o i l  (Available) P in soil  Testing  i n ppm  56 59  C h e m i c a l A n a l y s e s a t end of E x p e r i m e n t 62 metric  t/ha  64  of V a r i a n c e of Dry M a t t e r Y i e l d  of V a r i a n c e  f o r P-Uptake  a n d W a t e r Use E f f i c i e n c y  and C a l c u l a t e d  65  Y i e l d s o f Cowpea 103  vii  List  Line-Source  of  1.  The  2.  Schematic  3.  Experimental  Design  4.  Experimental  units  5.  Moisture  6.  Extractable  P  7.  Interaction  of  8.  Examination of S x P I n t e r a c t i o n parametric comparison  of  a  Sprinkler  Figures  Test  System  Plot and and  40 System  soil  Retention Curves in Soil S  35  and  at P  Layout  sampling  of end  i n the sites  Experimental of  Field  ...45 soil  58  Experiment  Treatments  on on  61  Yield Yield  ...41  73 -  non74  9.  Interaction  of  W  and  P  Treatments  on  Yield  75  10.  Interaction  of  S  and  P  Treatments  on  P-Uptake  89  11.  Interaction  of  W  and  P  Treatments  on  P-Uptake  90  12.  Cowpea  Dry  13.  Applied  P  14.  Mitscherlich  Matter as  Yield  Related Equation  to  as  Related  Bray-1  and  Yield  to  Seasonal  Extractable Curves  P  E T ..... 94 104 105  Acknowledgement I have gone t h r o u g h e x p e r i e n c e s of v a r y i n g d e g r e e s of ease and harshness but the d i f f i c u l t y e n c o u n t e r e d i n this phase of my pursuit was u n p r e c e d e n t e d . My d e e p l y h e a r t - f e l t g r a t i t u d e goes t o D r . S i e t a n C h i e n g whose m o r a l a n d financial support during the major duration of this endeavour went beyond academic acquaintance. I am also indebted to him for his thorough s u p e r v i s i o n of t h i s thesis. P a r t i c u l a r m e n t i o n m u s t be made o f P a s t o r J u s t i n La-Nibetle with his f a m i l y . H i s t r u e l y C h r i s t i a n D i s c i p l i n e of s i m p l i c i t y w i t h an i n w a r d r e a l i t y , h i s f a m i l y ' s o u t w a r d l i f e - s t y l e o f love a n d , f a i t h i n t h e power and wisdom o f God t o p r o v i d e and f u l f i l l human needs a n d d e s i r e s w e r e m o s t e x e m p l a r y ; t h i s was o f d a i l y g u i d a n c e t o me t h r o u g h o u t t h i s s t u d y . This wonderful family's presence in my life was of immeasurable spiritual and psycological strengths. F i n a l l y , I a c k n o w l e d g e t h e c h a l l e n g e p o s e d t o me by b r o t h e r B i n s h a l ' s tremendous d r i v e f o r knowledge, N i m t u r ' s . p e c u l i a r , y e t e x c i t i n g a c a d e m i c a c c o m p l i s h m e n t s , D a n l a d i ' s sudden wake-up f r o m a s l u m b e r a n d B a n y o ' s g r a d u a l p r o g r e s s ; f a r away i n N i g e r i a , y e t they constituted a driving force that culminated in this achievement.  1  I.  1.1  Backqround  and Statement  Irrigation agricultural and  are s t i l l  improvements  regions to  in  the  Most  recognized  but improvement  being  in  reductions.  The t r a d i t i o n a l  inevitably, water  and  an  irrigate  irrigation  period  of water  fixed costs  frequency  and a maximization  the  in the root  crop  before  The  introduction as  sprinklers)  that  the soil  zone  the next  systems(such  quantities  encourages  economic moisture  both  and  ever-  in  arid  on  farms  drought-induced  yield  application  systems  impose,  of a b r i e f by a  and  the  with  changed  extraction-dominated  to  period  These  of much  systems  understandably, of  quantity  of t h i s  water  pressurized  the  and  to  used  by  1975).  centre-pivot in  cost  the irrigation process  water  irrigation  field  no a d d i t i o n a l  the  irrigation of  and Raats,  systems  water  by  almost  relatively  the crops.  (Rawlins  trickle  as d e s i r e d  picture  by  sophisticated  distribute  of  with  the minimization  irrigation of  greater  is  water  and the p r o p o r t i o n  solid-set  as often  of  i s supplied  followed  application,  constraint  both  management  consisting  extraction  f o r each  of  sprinkler  the s o i l  economic  stored  water  methods  cycle  into  supplies  to prevent  solid-set  infiltration  extended have  to  f o r even  i n the l i g h t  water  methods  droughts.  irrigation  when  basin  seen  where  known  in irrigation  T h e demand  c a n be  temporary  determining  furrow,  made.  regions,  or l e s s  concern  a s one o f t h e o l d e s t  f o r l i m i t e d water  i n humid  more  of the Problem  future  competition  and  offset  i s widely  technologies,  practices  increasing  INTRODUCTION  reversed  cycle one  small  from  that  a is  2  predominantly  infiltration.  laws g o v e r n i n g water not  flow w i t h i n  apply previously.  be u p d a t e d . the  Yet.it  modification  This  brought  the s o i l  i s cautioned that of  the a e r i a l  S i n c e the development  sprinkler with  suggest  soil  systems  the  latter  emerges.  from  current  use e f f i c i e n c y  calls  the  procedures sporadic  geography  o f s u r f a c e and crop  pests.  does  not  solid-set  productivity  (low-frequency)  from  modern  rate  systems  but  and b e t t e r  and how  growing need  to  for  a  need  to  address  f a r m w a t e r management p r a c t i c e s w i t h a v i e w  decision  f o r an  much w a t e r  season, be  savings  fertilizer  t h e c o a s t a l a r e a of B r i t i s h  during  to apply.  Columbia  to  increased  management.  irrigator  special  applied  alongside  i s determining  In  humid  areas  where r a i n f a l l  occurs  irrigation make e f f e c t i v e  management use o f  the  rainfall.  Irrigation are  This  most c r i t i c a l  when t o i r r i g a t e like  systems  long-interval  i m p r o v i n g w a t e r c o s t and e n e r g y  The  on t h e  T h e i r e n e r g y demand and w a t e r c o n s u m p t i o n  resources.  carefully,  water  to which  o t h e r u s e r s o f t h e s e t w o ( w a t e r and e n e r g y ) e x t r e m e l y  important  to  environments  improve  c o n t i n u e t o f a c e c o m p e t i t i o n not o n l y also  method,  of h i g h - f r e q u e n c y  inherently  to  this  depending  replacement  did  had  e n d e m i c d i s e a s e s and  systems, the c h a l l e n g e t o  these  frequently  t h e r e i s by  and  the a r e a , c l i m a t e , crop v a r i e t y ,  necessarily  which  C o n s e q u e n t l y , management c r i t e r i a  the v a r i o u s c r o p s respond d i f f e r e n t l y of  i n t o p l a y a s e t of  readily  s c h e d u l i n g o b j e c t i v e s v a r y : when w a t e r available  o b j e c t i v e of s c h e d u l i n g  and  irrigation  costs  for maximizing y i e l d  per  are unit  supplies low, area  the is  3  obvious  and  irrigation increase  may  be  economically  justified;  w a t e r s u p p l i e s become more l i m i t e d i n an a r e a ,  t h e management  o p t i m i z i n g p r o d u c t i o n per u n i t methods  o r as water  water.  there  a r e those  profit  - i n a b r o a d s e n s e , and m i n i m i z i n g e n e r g y  These  objectives  stage  irrigation"  set forth proposed  "evapotranspiration(ET)  method"  i n t r o d u c e d by H i l e r  the  major  (1972)  irrigation  The are:  criteria  predetermined  (BCMAF, 1 9 8 3 ) obtain the  growth  as that depth  technical  Grimes  irrigation"  crop  (1961);  developed  and " s t r e s s  techniques.  by  day index  They were d e v e l o p e d  i n the e f f e c t i v e  rooting  irrigated  r o o t i n g zone t o  r o o t i n g depth  i s def-ined  i n the s o i l  above  the roots  water  a t some g i v e n s o i l  irrigation  Essentially,  or  depth  for either  i s needed depends  characteristics  i n the preceding  which  between i r r i g a t i o n s ] ,  The v a l u e o n e c h o o s e s that  be  [effective  (ii)  to a of these  on  soil  and stage of p l a n t  the scheduling  paragraph  r a m i f i c a t i o n s may be s a i d  following (a)  level.  (Cary,l98l).  highlighted  the  of water  level  to indicate  properties,  and  and C l a r k ( l 9 7 l ) ; amongst o t h e r s , a s  decrease of water p o t e n t i a l  criteria  Musick  growth  criteria.  90% o r more o f t h e i r  predetermined  addition,  requirements.  f o r d e c i d i n g when a c r o p s h o u l d  ( i ) the d e p l e t i o n  some  by  scheduling  on t h e b a s i s o f d e f i n e d  In  the concepts of " c r i t i c a l  and M i l l e r ( 1 9 7 6 ) ;  eta l  costs  o b j e c t i v e s a r e m a x i m i z i n g net  deficit  Woodruff  as  o b j e c t i v e may s h i f t t o  of applied  whose  however,  procedures  and t h e i r  to d i f f e r  various  from each o t h e r i n  ways:  filling  t h e maximum  expected  root  zone  to  field  4  capacity  on  an  interval  basis  throughout  the  crop's  1i fespan, (b)  filling  the  only  at  (c)  sequencing  such  that  (d)  some  effective  'critical'  the  of  crop  applying  water  refill  the  to  irrigation). rate  to  crop  This  meet  thereby  matric  stage  the  ET  may  not  soil  be  daily  growth  of  within  adversely but  in  not  the  capacity  crop, growth  affected,  amounts  insufficient  applying  zone  ion  at  period  and  (high-frequency  advocates  root  field  the  evapotranspirat  the  but  to  profile  approach  keeping  of  zone  deficits  frequently  the  potential  rooting  deficit  water  at  demand  of  the  constantly  necessarily  at  or  a  high  above  field  capac i t y .  This second  study  and  incorporated,  fourth  of  wetness  levels  almost  these  explicitly,  basic  principles  the of  first,  irrigation  scheduling. At  soil  seasonal not  be  plant  the  evapotranspiration  achieved. lodging,  higher  Factors  optimum  incidence  management  yield.  Thus,  as  irrigation  receptive  any  low  that  relative  one  include to  (i)  costs  as  conducive  hence  zone  availability  and  may  contribute  Jensen  that  particlar the of  cost  of  optimum  yield  may  the  not  irrigation  been  water  would  of  achieve  despite  method  for  failure  otherwise  observed,  that  deficiency,  potential  towards  have  practices  rates  the  scheduling of  high  aeration  would  (1975)  operators  to  yield,  root  process  availability, to  are  and  such  nutrient  disease  water  reasons  that  their  greatly because is  improve  of  often water  5  management, improper  (ii) yield  fertilization  recognized  or  decisions  generally  background  crop-soil-climate scheduling  management improved be  soil  strong  which,  nutrient  could  testing  only  other  and  interpreting  farm  combination Soil  of  harvest  concentration development have  adopting  practices, so  and as  soil  of each or  detrimental  to  is  supply  particular,  will  to yield.  the  new  will  under  a  give  a  Such  a  technique,  in combination  finally,  to  arrive  leads  influence  nutrient  the time limited  evaluating at the  authors  use  in  increased  by  of  onset  of  and,  the  root  on y i e l d  state  leaf  and  that  soil  the  best  ways:  area  and  moisture  by crop  drought for  Turner,  nitrogen  proliferation,  when  use  strategy  (Begg  different  to increased  water  uptake  i s not l i m i t e d  these  water  effects  total  of both  water  water  influence  can markedly  In t u r n ,  function  where  phosphorus  produces  method  applied)  respect  adopt  fertilizer  control, a  complex  would  with  and c o n s i s t e n t l y  results  status  1966).  is a  In  reliably  the  or  with  through  of a  practices.  where  irrigation 1976).  found  limited  to a p a r t i c u l a r crop  (native  management  nutrient  (Black,  stress  be  and pest  easily  management  with  the i r r i g a t o r  Furthermore,  applied  capability  i t accurately,  with  at  when  people  integrated  weed  the farm.  status  predictive  method  crop  from  a r e not  i n t h e management  when  and  irrigations,  irrigation  busy  Typically,  farm,  net income  irrigations  by  that,  by d e l a y e d  ( i i i )  training  system.  the  preferred  known  and  and  made  procedure  on  caused  and e x c e s s i v e  quantified  are  technical  that  reductions  and  higher prolonged  but both  can  is limited.  6  Nutrient surface out in  levels and t h i s  in a drying nutrient  according  but  with  Southern  not only  spite  of water  and  are  quite  irrigation  advantages controlling work  stored  1980) w o r k i n g  of the United Deboer were  such  as  effective  on s p r i n g  the greenhouse  on c o r n  findings,  technique  wheat  at Lethbridge  of  Hobbs  frequently  was  Research  deficit directly  but  Musick  for are  f o r corn, depth.  high-frequency, and  that  precipitation,  supplies  lysimeters station,  use  Krogman(1978)  bright  summer  in the  a water  that  and  been  (units  and sorghum  found  nutrient  i n outdoor  have  interval)  obtained  or  wheat.  by a p p l i c a t i o n  prospects  and m a i n t a i n i n g  results  efficiency  States,  use  and  use e f f e c i e n c y  et_ a l _ ( 1 9 7 7 )  the  scheduling  drainage was  that  corn  (long  use  laboratory  per i r r i g a t i o n ,  not a f f e c t e d  the c o n f l i c t i n g  optimistic  that  water  irrigating  t o low f r e q u e n c y  increase.  of  of  also  high-frequency  are  on  but  role  season.  crop  most  the  to dry  special  alone  and  water  of water)  reported  a  of  conflicting  to the r e l a t i v e  Keller(l965)  plays  effect  emphases  studies,  per unit  Plains  the  near  i s the f i r s t  the cropping  efficiency  placed  limited  as compared  High  on  highest  t h e amount  conducted,  and have  use e f f i c i e n c i e s  In  moisture  through  studies  been  (1971  efficiency  in  Available  to the depth  Dusek  Their  cycle.  regard  irrigation.  light  profile  these  lightly  water  of the s o i l  production  related  field  irrigation  based  with  and  portion  have  greenhouse  crop  usually  many  on  efficiency  reported  the  to i t s d i s t r i b u t i o n during  irrigation  Even  are  uptake  Although  of  in  abound.  as well  Canada.  as  7  1 .2  Study  Objectives  This soil  study  water  designed  to  was  and  soil  test  the  unguiculata  [L.]  Africa  cowpea  for  where  i t s grains  crops sole  practices, nutrients grown  i t the  alone.  The  and  supplied with  1.  i s the  most  growth  ways  and  It  other  know  i s aimed  pea,  "more  of  this  phosphorus  important"  much of  when  that  grown  Under  as  a  these  water  growth  gaining  crop  West  cultivated  how  at  Vigna  cowpea  stages  irrigation  with  experiment  (particularly  is rarely  to  response  resources:  field  legume)  i t s various  study  two  appreciably.  difficult  fertilized  a  tropics  important  supplementary  an  and when  insight  monocropped  i s scheduled  fertilizer  in  in a  climate. The  objectives  of  To  investigate to  climatic  c o n d i t i o n s of  2.  evaluate  To  different  of  To  irrigation  the  which  this  water the  method  (based  on  were:  growth and  use  saves  rate  phosphorus  coastal  area  of  efficiency  scheduling  unpredictable  make  study  cowpea  water  irrigation  identifying  3.  the  irrigated  yield  response  use  i t  with  cowpea(black-eyed  conditions.  r e q u i r e s at  and  of  was  intercropped with  proposed  the  humid  In  becomes  into  various  Walp.).  is  crop  It  performance  rain-fed  neither  fundamentally  nutrient.  is often  under crop,  concerned  and  dry  matter  fertilizer British  under  this  crop  techniques  with  a  and  makes  the  the  Columbia,  of  water  yield  most  under  view  to  optimum  rains,  1 and  2)  p r e l i m i n a r y recommendations  of  8  fertilizer  P  and  irrigation  water  management  forage  in  4.  develop  To  the  the  Upon  a  irrigate  of  cowpea  and  drought which  this  of  the  the of  this  irrigation annual (1981)  in  regions:  (a)  the  coincide  with  the  holding  capacity  adequate  water  restricted  limits  soil  had  this  three  given  often  crops  during  due  to  availability  the  at  that  the  agronomic  an  attempt drought-  light  on  among  the  degree  grouping.  the  economical  of  not  deficit  plants.  even  rainfall  e t a_l  in  humid  does  (b)  sufficient  impedance  of  though  Lambert  rainfall  to  Moreover,  irrigation  distribution,  of  The  validity  situation.  been  In crop  environment  taxonomic  mechanical to  of  largely  found  to  is  predicting  tolerance  necessitating  generally  for  (soil).  evapotranspiration.  evapotranspiration  crop  rain-fed conditions.  distribution  soil  is  with-  more  set  curious  drought  than  for  surface  that  more  optimal  and  experimental  factors  annual  rooting  water  the  becomes  in  throw  has  exceeds  for  of  a  legume  adapted  areas  of  cultivation  Ludlow(1976),  will  in  humid  out  a  associated  study  rainfall point  and  was  statement  an  response  one  variation  plants  as  function)  under the  as  c u l t i v a t e d under  L e v i t t ( 1 972) tolerance  results  pea,  normally  the  well  response  consideration,  black-eyed  summary  species,  (c)  (some  s p e c i f i c a t i o n s of  first  resistant  for  levels  in question,  tool  performance  management  to  procedure  environment  a  water  the to  not water  provide  periods  for  and  example,  9  11 . 2.1 E v a p o t r a n s p i r a t i o n , The  and  phenomena  and  sequential  This  the  of  and  water  in  water  contact  (Michael, is  movement  to  flow  1978).  thus,  evaporating  the  and  difference  leaf surfaces  plant the  root  water  as  water  of water  of  i n the  water  vapour  between  leaf  may soil  respectively the  everywhere  proportional  to  the  inversely  proportional  to  the  of water and/or  between  the  (partial  of pure  free  for  vapour  flow  transpiration  vapour  pressure  equivalent  potential  drops  s p e c i f i c free  liquid  and a t a t m o s p h e r i c  at  energy  w a t e r a t t h e same  pressure,  ISSS,1974)  t o -1000 b a r s o r l e s s , most  to  m a i n t a i n the water p o t e n t i a l of t h e level  and  p r o c e s s e s w o u l d have been s e v e r e l y leaf  surface,  1968; a n d H s i a o , 1 9 7 3 ) , a n d  potential  a i ri s typically  root  four  and t h e b u l k a i r .  water r e l a t i v e t o that  dry  into  The c o m p l e t e p a t h o f w a t e r  The p r i n c i p a l d r i v i n g f o r c e  t e m p e r a t u r e and h e i g h t in  the passage  i n the pathways  Although the t o t a l of  soil-plant-water  movement  with  is  energy gradient  resistance  a l l physical  the p o t e n t i a l d i f f e r e n c e  ( P i e r r e e_t a l , 1965; K o z l o w s k i ,  potential  are  complex  i n t o the root,  out of the l e a v e s .  atmosphere  of  roots  c o n t i n u o u s s y s t e m may be d i v i d e d  be a n a l y s e d by e v a l u a t i n g  rate  plant  c o n d u c t i n g e l e m e n t s and t h e  through  and  i n t o t h e s o i l ' and i t s r e t e n t i o n ,  to  constitute  and Y i e l d  p r o c e s s e s : the supply of water t o the  entry  plant's  of water  availability  relationship.  the  Crop Growth  rate of entry  movement  LITERATURE REVIEW  moves f r o m t h e s o i l  i n h i b i t e d by -10 b a r s .  leaf  above  the  time  Therefore, to this  i n t o the plant  critical  through the  10  transpiration impeding that  stream  water  to  loss  i n the pathway  the  atmosphere,  from  the leaf  supplying  water  the  must  flow  resistance  be a t l e a s t  to i t  (Rawlins  100  and  times Raats,  1975). Soil  water  transpiration which  insofar  allows  assimilation Most  potential  from,  permanent  and water  wilting  in  high,  i s , small  When stomatal water  the  leaf  at  assimilation. Hsiao,  expansion (that  conversion potential  rate  is  levels  of  generally and  of leaf  above  completely  i s not l i m i t i n g remains  and  high  unimpaired yield  throughout  is  of  and accepted  (Slatyer,  1976)  (i)  that  high  turgor  potential - a  term  to  growth (the  at leaf  stomatal  In e f f e c t ,  turgor  analogous  ( i i ) plant  cause  cell  pressure  due t o  t i s s u e ) ceases  rate.  loss  dioxide  walls  which  range,  carbon  require  and  i s very  1960).  excessive  water  water  to plant  preventing  levels  those  soil  critical  cell  in transpiration  the  the plant  a  Turner,  component  in soils)  stage  known  processes  on  by t h e t i m e  into  dioxide  the atmosphere.  decreased  division  much  into  and  or closure  carbon  (Gardner,  drops  of assimilates to l i v i n g  proceeds  potential  value  rate  opening  availability  to close,  outward  escape  a t which  of water  expense  pressure  a decrease  growth  point  1973; a n d Begg  acting  hydrostatic  and  " I t  potential  pressure  begin  stomatal  are affected  potential  the  and  vapour  negative  water  openings  even  1969;  range  photosynthetic  respectively,  processes  potential that  i t controls  or _ inhibits  physiological  reaches  as  affects  i n most  water  closure crops,  i f the evapotranspiration maximal  the l i f e  only  when  of the crop.  water Often,  11  however, most  crop  production  crops,  keeping  continuously  ample per  unit  production  per  unit  Maximizing  water  may  not  irrigation) watered' and  by  plants  imposed  growing  regimes  does  fully  explore  They  agree  yields to  but  ensuring  but  that  limited  this  yield  deficit  an  maintaining  wet root  diffusion  into  poorly  al,  plants  respiration 1980 ), are  necessary  and  still  transpiration  as  a  not  by  for  water which  growth  subject  water  consequence  how  of  (no  'wellHillel to  decreasing to  an  ET,  externally for  argue  wellthat  of  water  i t  limited  supplies.  decrease  directly  crop  proportional  potential can  excessively  of  Veits  promising  presumably  development. and  of  crop.  leaf  regardless to  more  costly  be  by  than  implications  will  maximum  production.  subject  and/or  in  dryland  (1975)  soil  drained  on  efficiently  Hiler  ensuring  out  and  the  high  pointed  is valid  may  on  excessively restrict  are  by  guaranteed.  statement  irrigation  imposed  and  et  short  as  than  possible  decrease  exchange  root  field  not  of  For  maximization  is  appears  yields  Howell  of  more  i t  This  the  regions  Besides,  the  results  grown  levels  that  in  in  the' water  lower  demand.  crop  irrigation  much  water  increasing crop  watered not  use  crops  this.  high  simultaneous  (Wue)  since  permit  soil  consumed  efficiency  state  evaporative  a  not  potential  the  but  water  at  (1973)  Wue  from  desirable  but  water  area  frequently  Guron  since  of  use  be  crops,  increase  plant  supply  production  (1962)  c o n s t r a i n t s do  wet  on the  the  impair  entail gaseous  Restricted  oxygen  wet  limits  soils  one  soil  stress during increased  may  water  hand  is  (Stegman  kept,  periods  crop  of  high  potential  drop  12  across  resistances  within'them  on  the  other  (Rawlins  and  Raats,  1975). Thus,  i t i s obvious  moisture  content  physiological production, occupied,  either  undergo  water  subject  of  decrease that  on  net  1973)  for  used  repeated  decrease  potential  and  for  days  such  and  which  may  irrigation an  are  also  water  periods  of  in  The  management of  frequencies water  dry (that  stress  such  unit  is  to  stops  Hsiao  long  do  assimilates  can  effects  rate,  and  be  cause  can  relieved.  then  Hence, maximum  affect  stress  not  observed  mid-afternoon  that  yield lasts  rain-fed agriculture  or  latter  statement  is,  or  is  surface  matter  from  water  slightly  the  delicate  leaf  frequent  forms  the  to  decreased  inevitable in  and  crops  growth  stress  less  land  plant  potential  only  of  on  long.  in  matter  results  stress  growth,  as  may  of  per  stress  soil  optimum  dry  non-stomatal  when  for  permitting  slows  too  the  growth  times  occur  methods.  investigation  irrigation  from  periods,  i s at  not  before  preferable  as  of  depressed  stresses,  evapotranspiration  water  growth  are  in  or  high  of  Fortunately,  plant  of  used  water  periods  hours  accelerated  brief  scheduling  that  standpoint  advantage  timing.  constantly  desirable  water  Avoiding  period  to  the  of  no  i f they  several  in  be  which  each  from  a f t e r e f f e c t s of  growth  photosynthesis be  the  during  during  stored  to  a  always  unit  stress.  (Hsiao,  potential  but  per  seems  maintaining  not  irrigation  experiments suggest  is  processes  there  that  interval  basis  is  programming  fundamental  for  production  irrigation  this  under of  different'durations  one in  in  study: variable or  the  more crop's  13  growth crop  span).  yield  yield  Literature  and  ET  (both  variations  are  accuracy  and  production function  to  concave  that the  and  of  its  further  fertility  relationship water)  range  by  measurement  or  linear  the  to  interaction  of  The  type  of  estimation  associated with  for  that  functions.  et. a l , 1980)  is reserved  between  reveals  from  response  influences  The  of  can  (Stegman  varied  soil  use  convex)  i s chosen,  conditions.  with  subject  water  influenced  parameter  the  consumptive  relationships  curvilinear  water  (or  on  site  and  this  response  in  section  which  emanates  review  2.3.  2 .2  Irrigation An  from  optimal  a  good  depletion, the  amount  This the  irrigation  program  the of  of  alternatives  accomplished soil  using  moisture  Estimated  rates  determinations basis  for  perhaps  the  adequate  that  the of  days  should  oldest  which  blocks  as  knowledge  moisture of  exist.  the  of  of  use  moisture  of  implies  such soil  coupled  scheduling complete  moisture  the  Such content  procedure right  scheduling as  -  time, can  be  tensiometers  moisture with  1970)  and  irrigation.  provide  (Jensen,  reservoir. soil  each  at  moisture  irrigation,  scheduling  water  methods  soil  next  Irrigation  indicators  method  the  irrigation  amount  soil  one  a p p l i e d at  irrigations  irrigation  soil  be  be  estimate  before  consumptive  known  would  to  reading  existing  predicting  an  right  direct  of  of  Efficient available  of  constitutes  application  regime  developed  number  water  program  many  and  Scheduling  content.  gravimetric  an  excellent  and  constitute  irrigation. control  of  control  requires  at  a l l  the  times,  14  and  the  application  reservoir for  salt  to the d e s i r e d  literature  regarding plant moisture  maintains  by  that  point  there  the  others,  that  exists  over  irrigation  much  design  soil  of s o i l  of s o i l rates these  and s c h e d u l i n g .  t h e o r y , advocates of et a l ,  moisture uniformly well  content  optimal i r r i g a t i o n  whenever t h i s However,  point  and  availability a b o v e PWP may  yields.  and  Little  as t h e l a t t e r application  The r e a s o n  i s clear:  that  to  in  i f the  plants  indeed  i n t h e whole range  between as  the  h a s n o t r e a c h e d PWP a n d i t f o l l o w s  that  regime  as  long  i s one i n w h i c h w a t e r  is  applied  i s reached.  several  H a g a n , 1967; J e n s e n ,  the  views  PWP a n d FC, t h e n t h e r e i s no need t o i r r i g a t e moisture  (1959)  differentially  final  theory i s j u s t i f i e d ,  1955)  the available  m o i s t u r e , even  acceptability  and  between permanent  within  opposing  one t h e o r y ,  (1950  respond  and  soil  m o i s t u r e by p l a n t s i s  Hagan  do  theories  different  (FC) c a l l e d  content  wider  Veihmeyer-Hendrickson  and  Hendrickson  capacity  moisture  controversy  the  this  requirement  be two m a j o r  t h e whole range  plants  growth  soil  refill  to the i r r i g a t o r :  (1939),  that depletion  of  to  (AWSC); t h e o p p o s i n g  reduce  utilize  to  leaching  supply  utilization  appreciably  is  and  Taylor  in soil  and  water  throughout  and  claims  variations  to  (PWP) a n d f i e l d  which are F u r r  theory  water  the  appears  Veihmeyer  storage capacity  range,  plus  that are helpful  uniformly effective  water  enough  level,  response  levels  forward  wilting  just  c o n t r o l where n e c e s s a r y .  From  put  of  points 1968;  h a v e been p u t f o r w a r d  Denmead  and  Shaw,  ( H a i s e and  1962;  Stewart  1 5  et  al,  1975;  moisture  depletion  percentage enough  and  English  to approach  because,  water  this  from  wilting  moisture  characteristic  a  decrease  increase water the  in  may f a i l  mass  of s o i l  elongate above cost only of  o f water  i s allowed  application depression  i s i s  availability Manual,  into  be  value  be  in  avoided.  in this  The procedure  on  of the crop  the  by  of  being  an  effect,  storage  irrigation  water and  capacity  before  water  economic  yield  of  AWSC  Irrigation estimate the  concept  to  cultivated,  on t h e m a r k e t ' v a l u e This  of  into  roots  i s still  percentage  gives  In  o f water  crop  i n B.C.  great  availability  stress-induced This  a  (b) supply  failure there  where  was  or  Design of  the  availability of the crop implicitly  scheduling  techniques  irrigation  scheduling  investigation.  experiment by  of  soil.  in  o f movement  where  (soil  i n the region  results  (c)  (as defined  depending  particular three  curve  depleted i f  to obtain  moisture  of t h e water,  regions  deficit.  i s changed  on a n y  utilized  water  wilting  of t h e a v a i l a b l e water  to  coefficient  permanent  t o (a) p o s i t i o n oft h e  and (d) depending  necessary  to  soil  coefficient  interval  roots,  1 9 8 3 ) m u l t i p l i e d b y t h e AWSC  maximum  adopted  fraction  allowing  of the crop  content  t o removal  by  point,  against  on t h e e n e r g y - s o i l  a n d t h e market  a defined  part  of the slowness  dried  the w i l t i n g  in  moisture  r a p i d l y enough  the soil  grown  because  the  failure  or retention)  resistance  1982)  closely,  due  percentage  in  Nuss,  may c a u s e  soil  permanent  slight  and  which  between  was  based  there  irrigations  on  an  was a - f i x e d  and equal  f o r any given  length  scheduling  of time  technique.  16  The  concept  frequency  matric  allowing  gradual  permanent  the  with  effective  p o t e n t i a l and extraction  wilting  is  application  percolation  interval"  (common  filling  high  This  "irrigation  method  completely to  of  and  method  often  may  possibly,  a  when  a  gravity  rooting  until  reached  is  to  systems) a  of  given  field  capacity  s t i p u l a t e d water  cause  runoff  crop  and  then  level  is applied  almost  low-  requiring  depth  irrigation  surface  typically  above again.  inevitably,  (Hobbs  and  deep  Krogman,  1978). According be  minimized  required  to  frequently supports with  Hobbs  or  even  enough  systems  store  high  and  rain  the  cropping  recorded  that  as  long  transpiration  (or  adding  water  significantly; bottom can  of  be  wasting  the  concluded  that  to  Phene  same  that  as  to  time  often  keep leave  This  means  deep the  only  a  factor  not  in  for  in  This applying  capacity regions  (1973)  had  to  the  of  soil  low  soils  matric  humid  demands  that  i t This  soil  is applied  to  is  high-frequency  Rawlins  more  can  than  occur.  that  meet  the  water  escape soil  a f f e c t i n g plant  percolation. reason  applying  sufficient  increase  allow  as  but  the  occurs  water  simply  zone.  water  does  Earlier,  not  less  capacities,  sufficient  should'  percolation  (1974)  evapotranspiration)  eliminated water  stress  by  season.  i t would root  profile,  storage  the  deep  applying  i t possible  at  during  by  moisture  low  make  (1978),  soil  suggestion  intermittent  extra  the  that  earlier  Krogman  eliminated  distinctively  potentials  and  replenish  the  irrigation  to  to  crop, content  out  the  water  content  growth  without  latter water  researcher in  excess  of  1 7  evapotranspirat to  provide  on  the  root  therefore, It  to  basis  control  known  sprinkling but  of small  evaporative  losses  admittedly,  deep  Using  of water  Rawlins  sytems pumping  rate.  be  by  irrigation  a  depend  of  application  gained  by They  largely  pressure), rate,  designing  which and the  pipe  in turn  of  water  over  of  the  soil,  and  water  and  deep  add  that  increases  surfaces  but  avoided. can  be  exist is  with  faced  the s o i l  a  this with  surface  requiring and  highly  a  to  minimum  fixed  cost  water. out  frequency  observed  that  size  for  certain  economic  irrigation  the c a p i t a l  (within  depends  therefore system  be  which  pointed  high  upon  soil  frequency  coverage,  (1975)  water  further  alternatives  of  soil  runoff  would  to the f i e l d  to achieve  of  design  a n d wet  flow  or  frequently  irrigation  turnout  Raats  more  and r u n o f f  surface  systems.  Delivery  minimized  each  and  to  pressurized  from  good  (1978)  sprays  scheduling  with  simply  with  nozzle  of  out a t the bottom  eliminates  Krogman  instead  rate  capacity  with  of water  constaints  water  associated  the  from  Various  fundamental  such  amount  percolation  unlike  distribute  that  and  sprinklers,  manipulated.  holding  is  and,  the  of water  inherently  Hobbs  application  benefits  water  management  potential  adjust  the f l u x  unimportant.  well  water  only  becomes  percolation  depth  need  irrigation  salinity  of s o i l  The  management,  the  control  zone.  is  technology  high-frequency  to  the i r r i g a t o r  application the  under  leaching  irrigating content,  ion  upon  capital  the  costs limit  water costs,  continuous  with of of  delivery c a n be  operation.  1  They the  added root  yields  furthermore,  environment could  be  conclusions  were  the  to  crop  is  component  of  maintenance frequency  of or  soil  water.  implicit  assumptions:  the  pipe  increase  frequency but and  (long  wider of  irrigation  deficit  i n amounts crops In  the  A  cost  labour,  is  the  These that  dominant  pumping  cost  significantly  range will  too  method)  from  low  to  experience of  and  with  soil  which  none  at  refill  prevent  high-  will  the  moderate  moisture will  the  a l l to  the  water  will  be  more  deficit fluctuate by  experienced  severe.  profile  decline  followed  stress  be  stress  low-frequency  irrigation  during  then  irrigation,  case  heavy  extraction  will  will  interval  range.  full  A  and  a by  subsequent  the  pattern  itself.  Whether watering  question  yields  will  regimes  is  yields  of  differ  i s an  of  sugar  appeared Hobbs  and  findings. conclusions  Miller  beets,  to  significantly  or  essential question.  inconclusive.  irrigation.  frequencies  opposite  of  not  crop  Miller's  minimum  will  the  Results  irrigated,  maximum  that  costs  moisture  a  deficit  several  optimize  so  that  period  good  a  may  use  and  continuously.  repeats  on  water  cost,  long  two  fully  with  irrigations  system  high  irrigation within  predicted  be  frequent  reducing  realized  frequently  less  while  .  irrigation.  With applied  that  8  wheat  (1976)  not  under  Research  reported  beans  According  to  Miller,  the  mitigate  the  effects  of  water  in  Canada  However, in  (1978) other  similar  on  wheat workers  studies.  a  on  this  relatively  and  Krogman  in  these  high-frequency high  have  irrigation deficits. supported  arrived  Federes  and  at Faci  1 9  (1980)  found  irrigation under  were  normal  lower  yields the  same  reported  t o the lower  technique.  For  irrigation  frequency  irrigation  can a t the  research  produced  will  under  as,  frequencies with  yields  attributed that  that  or lower  t h e same  under  the  yields  best  certainly  be be  than,  levels  under  The  regime  were  associated the  deficit as  useful  produced  deficit.  therefore,  regarded a  yields  of  efficiency  moment,  on c r o p  high-frequency  high-frequency  application the  deficit  with  effect  of  high-frequency  uncertain.  contribution  This  in  this  production  has  direction.  2.3  Water  Supply  Today's stimulated  emphasis greater  crop  responses  are  several  received that used  and N u t r i e n t  efficient  concern  t o v a r i o u s growth factors  but  two that  reasons give  characteristics speaking,  land)  growth  determine  water  to  namely:  the best  of  the  Box  whether  the  field.  and s o i l  and Hunter  investigate There  fertility (1958)  have  observed  ( i ) to find  the. c o m b i n a t i o n s  yield  and  response  management  to  crop  response  The  in  used  describing  i n the neighbourhood  factors.  Crops  crop  factors  soil  the production approach for  to  f o r t h e methods  considerable attention.  variables  of  on  Availability  can  ( i i ) to  surface  responses  determine  (soil  of t h e optimum surface be  or  of the  broadly  combination  can then  modified  is  i f  be  used  to  conditions  change. The with  interactions  respect  critical  to their  review  of  between effect this  water  supply  on c r o p  yield  subject,  Black  and s o i l  is  fertility  complex.  (1966)  indicated  In  a  that  20  crop by  yield  may  a given  of  the  change  change,  supply. and  Begg  and  affected  there  containing high the  a  loss  soil  of  on  (1973), and  the e f f e c t s of  with  either  intermediate  conditions, partly  control  is  the  because  of  association  the  marketable  surface.  evapotranspiration surface  of  as  adequate  soil  the surface,  the  from  zero  up  control  an  and p a r t l y  yield  only  by  be  moist  However, partly  under  in  the  a minor  by  Black  and i s used  often  with  soil,  changing in  the in  Under  as d e f i n e d  i n forages  transpiration  primarily  increase  i n the plants.  canopy'  in  the  increase  soil.  may  an  in  t o t h e maximum  causes the  i n part f o r  occurred  condition,  i s in  where  bare  substitutes has  that  from  this  Differences  and  below  that  of v e g e t a t i v e  (1966),  the view  i s i n the atmosphere.  i n the s o i l  'density  holds  Under  canopy  the c o n t r o l  the  transpiring  and t h e water  evapotranspiration  depth  then  conditions,  transpiring  the magnitude  analyses  for evaporation  f o r water  support,  term  decreased  Hsiao  good  available  f o r water  of the s o i l .  evapotranspiration;  The  (1966),  conditions  a t some  plants  of vegetative  atmosphere,  under  on  level,  given  associated  of water  a v a i l a b l e water  will  have  in his contribution,  of c o n d u c t i v i t y  density  Black  or  water.  deficiency  portion  depending  fertility  (1962),  and  density  conductivity  surface in  soil  (1966)  is  soil  (1976)  yield  unaffected,  level,  of the information  by c a n o p y  Black  Veits  Turner  on  deficient  increased,  the i n i t i a l  o f most  fertilizers  be  in fertility  Furthermore,  summaries  or  evidently  expanse  fertility the  way  of  affect  expanse  of  by c h a n g i n g t h e  21  character  of  the  increase  in  crop  does  not produce  (ET);  on  the  differences small  the  fertility  An  of in  soil rate  despite  produce  many  can  a given  fertility  be  level dry  by  relatively that the  obtained  water  regime  by  may  be  and t h e c a p a b i l i t y matter  of d r y matter  under  of  water  by c r o p s  under  the  evapotranspiration  is  level  carry  than  at a comparatively  1976),  those  greater  (1966)  observed  rapidly  from  Two  in  supply  was a m p l e  largely  depleted  rapid  deficiency  ( i i ) differences  fertilized  fertilized  to  on  of water  variations  fertility  (Veits,  of use of  the latter  accumulation  could  occur:  an e x p e r i m e n t  i n which  from  a n d more and  wheatgrass growth  secondly, under  early  water  unfertilized  slowly  after  in  at a at level  1966; B e g g water  first,  at  was  Black  used  more  while  the  the a v a i l a b l e  water  t o Sneva  conditions  the season,  be  mechanism of  soil  according  desert  to  of p l a n t s  of  than  said  an  of a  photosynthesis  lower  i n rate  without  conditions  fertility  dry matter  more  fertility  induced  only  (a) c a p a b i l i t y  additional  made  in yield  including:  times.  (1958),  soil  an  evapotranspiration  in  that  under  use  for  ways  different  was  that  i s to say, i n essence,  additional  in  water  somewhat  Turner,  water  in  result  yield  i n production  increase  deficiency  greater  to  increase  achieved  This  fertility  increasing  differences may  in  suggests  circumstances.  appreciable  higher  i n ET.  by  increase  wide  on t h e i n i t i a l  crop  prevailing  and  contrary,  the s o i l  further  produced  of the increase  t o depend  Black  a corresponding  in soil  increasing  of  yield  differences  magnitude  said  surface.  in  et a_l Oregon  exhausted  more  22  rapidly than  the  did  water  the  supply  unfertilized  Although  nutrient  processes  in  available  water  nutrient  transport  the  quantity  the in  of  also,  the  in  the  water  et  al,  1981).  soil  water  greatest  (mass  of  amount  and  makes  of  experimental  an  earlier  absorption  plant  1972),  and  the  soil  intimately  soil  are  date  affects  independent necessity  for  related not  only  the  in  the  movement  to  the  by  diffusion  as  (1972)  water states  field  that  space  in  statement,  allows  form,  for  of  root  poses  ions  solution, and  flow (Unger  situation,  for  solution  the  best  diffusion, the  and  as  amount  root  field  oxygen  assuming  situations,  a  soil  the  for  diffusion  conditions  by  under  capacity  air  nutrient for  i s absorbed  and  especially  nutrient root  for  growth  of  area  last  at  volume)  near  of  matured  (Veits,  them  the  flow)  favourable  This  root the  in  and  water  sufficient  cross-sectional water  both  Veits  content  combination  and  times rate  soil,  grass.  plant  water  (concentration but  in  the  greatest  mass  flow  of  extension.  i t  is  true  clearly,  two  for  a l l  practical  challenges:  •  a  plant  growing  fluctuations soil  in  saturation  therefore constant the  i n . the  be soil  matric  requirement  field  water to  is  availability  drought.  The  confronted  with  water  suction  at  a  potential could  be  usually  met  at by  the  FC)  that  range  investigator  problem of  may  subject  1/3  of bar  from would  maintaining (which  approximately.  drainage  to  provisions  is This and  23  irrigation of t h i s •  a  s c h e d u l i n g p r e c i s i o n s - the  situation  analogous  or  free  (availability)  to the  energy  and  (quantity  factor)  replenishment  in  solution  soil  to  the  i s m e a s u r e d by 1981)  as  the  having  one  facet  then  has  the  t o be  satisfy  crop  soil  of  scheduling  a  solution  context  Sumner  nutrient  irrigation  c o n s u m p t i v e w a t e r use  to  guarantee  nutrient  to  replenish  But  liquid  fertilization  soil and  factor  to  Larsen  phase i s o n l y  t o t h e c r o p management p r o b l e m ; i t (diffusion  a  factor)  tremendous Boswell  problem  and  of c r o p s  words, f o r a p a r t i c u l a r of  optimal  (Sumner  according  and  to  form  the  maintain can  only  environment,  and  on  the that  correction  and,  and  adequate  considered  recommendations  a s t a t e d c r o p w o u l d be d i c t a t e d  t o which economic y i e l d  size  remark  timely be  The  effect  (1981) its  sufficient  of t h e w h o l e s o i l - p l a n t - a t m o s p h e r e c o n t i n u u m .  requirement  phase  i n view of the p o i n t above.  n u t r i e n t i n the  morphology of a r o o t system have  diagnoses  solid  t h e n e e d s of t h e p l a n t f o r h i g h y i e l d .  Thus,  soil  r a t i o of t h e change i n the q u a n t i t y  s u p p l i e d at a r a t e  extraction.  a  f a c t o r ) to ensure  system  factor.  the  ( s u p p l y ) , i s the  the c a p a c i t y f a c t o r d e f i n e d  a particular  of  in  the absorbable  (intensity  u n i t change i n i n t e n s i t y  (1967),  to  of  - water  or added i n the  of  a b s o r p t i o n by a g r o w i n g ability  of  in a given circumstance  continued  Boswell,  part  r e l a t i o n s h i p between  t h e amount p r e s e n t  amount o f n u t r i e n t p r e s e n t  solution  being  study.  potential  The  latter  response  by  will  the be  in In of  the other water  level  of  obtained.  24  Fertilizer surface  by  localised termed  below  'banding'  soluble water,  usually  used  or to  patterns  accumulation  row  the  subsoil  tend  to  favour  (Veits,  1972)  nutrients  adsorption  clays  availability  usually  contains  fertilizer The Veits  (1966),  Begg  and  indicates  nutrient  availability  uptake  and  Boswell  state  in root  the  in  to  of  meet  in  a  usually a  recent  application  of  irrigation  systems. coupled  c y c l i n g of  plants  and  surface  with  the  nutrients  from  earth-dwelling of  held  of  by  enough,  surface the  and  there  Unfortunately  concentrations  fauna  extractable  soil,  matter. most  plant,  through  the  the  evidence  Turner  that  plants in  so  rates  new, of  as  that  that  i t s demand,  into  or  crop  obtainable and  soil  that  soil  as  water  by  and  crop  would  to  and  have  soil nutrient  mass  speed areas  decreases nutrient Sumner  water  in  flow  will  of  in  supplies  and the  water  decrease up  of  Boswell  total  depletes  rate  works  and  concentration.  i t s growth  water  the  deficit  nutrient-laden  undepleted  in  Sumner  measured  reduced  principle, soil  (1976)  drought  to  a l t e r n a t i v e , the  extension  increase  and  in  of  sometimes  layer  unable  trickle  the  or  soil  in);  'fertigation',  land  the  entire  nutrients.  (1981)  is  by  fluctuates  preponderance  surface  the  and  organic  highest  by  concentrations  in  and  seed  application,  matter  surface  exchangeable on  to  fertilizer  the  or  to  the  ploughed  introduction  s p r i n k l e r and  organic  to  the  over  times  close  placement;  material  in  either  at  surface  describe  of  of  (and  the  fertilizer typically  water  applied  broadcasting  area  innovation  These  is  or  i t s rate  of  order  to  to  sustain  25  growth. With this  specific  study,  (1971),  and  phosphate  r e f e r e n c e to phosphate, the t e s t  most r e s e a r c h e r s H a g i n and  uptake  proliferation  by  is limited  soils,  influencing interact  c u l t i v a t e d and In  dry  influenced  i n movement. both  Therefore,  ion  conditions  or  paths  stress,  diffusion  i n the s o i l  not  well-irrigated  crops which  is may  reduced,  largely  through  ( M a r a i s and  to Black  plough  be  (1966),  soil  its  impaired  even i n t h e  layers  d e e p e r and  soil.  provided by That  i s t o say,  f a c e of d e f i c i e n t  of a s o i l  profile,  was high  regions, is usually  roots.  c o n d i t i o n s may deep  unfavourable  an  phosphate  irrigated  the s u b s o i l  that  by  1976).  i n h u m i d and goes d r y ,  It by  i n f l u e n c e on  Wiersma,  the  f o r by  ( O l s e n e_t a l , 1 9 6 1 ) .  f e r t i l i t y under t h e s e  inhibited  p r o p e r t i e s of t h e  upper  layer quickly  of s u b s o i l w a t e r ,  fertilizer  plants  compensated  t o d e p t h s b e y o n d t h e maximum e x t e n s i o n of c r o p  not  of  phosphate  presumably,  moist  is  ionic  fields,  the  roots  ~  root  content  and  when  t h e use  that  by  (H2PO4  s t r o n g l y w i t h p h o s p h o r u s u p t a k e by  moisture  in  view  moisture  shown f o r s o y b e a n t h a t p h o s p h o r u s u p t a k e was  increase  Williams  much  development'  i n phosphate c o n c e n t r a t i o n  According  common very  phosphate  root  (1967),  in  e u t r o p h i c ones a l l a l i k e .  diffusion  increase  is  utilizable  a b s o r p t i o n o f p h o p h o r u s by longer  (1982) h o l d the  crop  s i n c e the  species)  diffusion,  Turner  i n c l u d i n g Larsen  nutrient  t h a t , by water  a crop w i l l  of  chemical  i n c r e a s i n g the supply  be a b l e t o  denser root system to e x p l o r e deeper  increase  penetration  p h y s i c a l and  An  layers  in  the  develop of  the  26  soil  profile  (1972)  cautions  affecting from  one  soil's  main  store soil  the  have  low,  in  adds  perhaps  use  but  solution  and  which  is  to  up  in and  crop  P  dry  Veits  "drought"  nutrients  i t s water while  soil  the  lacking  some  species  of  species)  growing  in  absorb  when  of  is getting  wheat  other  periods  depends  in  locked  capability  kind  plant  that  many  recommendation,  another  deficient  some  the  this  the  however,  during  this  to  be  nutrients  sufficient  for  But  could  soil  of  He  (and  it is  soil  of  supply  wheatgrass  this  activity  roots.  soil  moisture.  that  root part  active  wet  for  sufficient  availability  on  the  concentration  duration  and  frequency  of  of the  P  and  in  surface  P  in  wet  the  or  dry  periods.  2.4  State  of  Knowledge  Cowpeas- ( V i g n a bean  production,  irrigation and  dry  than  p r a c t i c e s are  soybeans,  i s the  be  have  that  be  vegetative his  Research  Walp.)  are  grown  pods,  leaves  and  hay.  for  group,  both  shoot  for  dry  Efficient  biomas  practice to  grow  e_t a_l  by  in  (1980) a  production  influence  of  the  in a  proposed  that  vegetative  phase  Australia, larger  for  area  cowpea  and  Shouse  and of  in et  the crop.  several a_l  (1981)  r a i n - f r e e environment,  withholding  affecting  (1980)  during  undertaken  cowpeas  without  Hearn  applied  used  Turk for  the  be  been  reduced  stage  and  commercial  zones.  demonstrated may  could  could  studies  ecological  and  Cowpea  [L.]  needed  Constable  present  saved  Similar  use  unguiculata  mature.green  irrigations  water  Irrigated  beans.  For fewer  in  seed  irrigation yield.  vegetative  stage  But,  water  during added  drought  on  the Turk seed  27  yield  may  depend  flowering • of  from this  observations  can reduce emergence  may  working  on  vegetative  felt  when that  a  cowpea stage  at  was  following crop  the  vegetative  reported and  ones  that  stage  hand,  cowpea  vegetative  after  lower  d i d not  increase  production,  water  to  experienced  reduced  in nitrogen seed  the onset,  i s t o be  that i n seed  15 d a y s .  They  resumption  of  normal  drought. biomass  I n t h e same  The  production experiment,  biomass  production  yield  h a s been  vegetative  and r a i s e  subjected  the crop  found  permit  P t o cowpea  and Nangju,  from  (1983),  not  influence  of f e r t i l i z e r  and d i d not reduce  and H a l l  fertilization.  nodulation,  the reduction  cultivars,  did  shoot  well-watered.  period  occurs  stage  1980; a n d Kang  stage  Clearly,  record  the  stress  of  probably  one  moisture  reductions  at intervals  vegetative  nitrogen  dry matter  Rhoades,  whether  drought  t o improve  1965;  small,  were  Ziska  significant  growth  the  application  hence  however,  of  when  California,  treatment  d i d in fact  low o r h i g h The  irrigated  irrigation  irrigation harvested  experiment,  caused  during  during  with  that  determinate  yields  Riverside,  drought  the crop this  e_t a_l ( 1 9 7 6 )  but with  affect  recent  recovery  under  flower,  conditions  i n agreement  productivity considerably  sufficient  than  o f Summer f i e l d  to first  In  environmental  This' i s p a r t l y  not s i g n i f i c a n t l y  thereafter.  yield  subsequent  and pod f i l l i n g .  the  stress  upon  grain  1983).  stress seasonal supply  On  the  (Tewari,  the  other active  fixation;  plants  was  1965).  t h e i n v e s t i g a t o r must  irrigated  rate  the  nitrogen  to  (Tewari,  growth  yield  during  widely  be a w a r e o f  f o r hay o r i t s beans  because  28  of  several unequivocal These  such  major  findings  i.  highlights  i n themselves  Major  increases  achieved  by  emergence  to  floral is  findings in different  i n water  the  first  providing  i n the s o i l  a  however  (Allen  profitable  i f yields  i i .  may  be  luxuriant hay  cultivated  and stem  has  no  seed  yield  i i i . by  real  advantage  (Kang  Vegetative Zisk  or fresh  production  and H a l l  economic  close  soil  seed  and Nangju,  1983).  stage  stress  water  (1983)  to result  maximum  of the  crop.  nitrogen to  favour  cowpea i s excessive  superfluous and  has been  and  desirable  Where  f o r pod p r o d u c t i o n  be  in applied  production,  i s considered  only  to  i s very  forage.  water  analysis  will  combine  This  of  circumstances  reductions  abundant  plant  precipitation  to the value  production.  f o r commercial  leaf  from  availability  production  supply  no  be  macroscopic  deficits  are maintained  moisture,  foliage  1971),  may  from  I n many  water  compared  phosphorus  and  though  expected:  of  'reasonable'  1983).  guide  efficiency  appearance  the savings  small  Excessive  high  in  planned  because  useful  irrigation  and Lambert,  that  water  use  profile  ( Z i s k a and H a l l ,  indicates  as a  are not u n i v e r s a l l y  occurs  levels  serve  withholding  buds,  present  would  environments.  and  ultimate  observed  in increased  damage  29  due  to  lesser  Elasmopalpus  liqnosellus  Macrophomina  phaseoli  stage  of  fungi,  virus  Sinha,  It  crop  appears  agree  cowpea  that  diversity  of  Ziska  effects  are  irrigation of  (or rot at  ( any  attack 1974  yield  and could  be  and  by and  used  cultural  and  in  to  develop  cowpea  production  are  site  specific,  integrating  environmental  effects.  experimental  studies  application, needed  for  areas  where  crop  water  present. cowpea  yield  and  soil  functions  a  range  study, in  for  the  conducted a  humid  crop to  of  and  these  because  relatively for  cowpea,  fertilizer uptake  especially  are  not  obtain  environment  India  functions.  phosphorus  management,  in  value  Therefore,  and  This  unreasonable.  production  development  functions  performance  States  irrigation,  fertility  nitrogen  (1974)  limited  most  irrigation  versus  of  did  greater than  of  relating  production field  are  a  conditions  United  broad  (1977)  under  Malik  California,  the  Sinha  irrigation  r e s p e c t i v e l y by  (1983)  and  for  interactive effects  fertilizer  studied  Hall  The  understood  satisfactorily  soil  crops.  responsible  crop  about  chances  (Summerfield,  factors  poorly  climatic,  were  unquantified  not  Frequent  these  they  at  charcoal  increases  the  can  phosphorus  fertilizer  But  cowpeas  leguminous  versus  borer'  and  nematodes  that  of  other  and  )  ).  growth  stalk  1977).  adaptation  and  corn  are in  available information  is  therefore,  30  III.  A.  EXPERIMENTAL  3. 1 I r r i g a t i o n The sprinkler  elsewhere  design ( BCMAF,  on  the  data  from  University  utilized  (Appendix  according  i s  a  for this  essentially  Class  A).  Crop  weather  British  those  hand-move study.  as  The  described  of  A  in conjunction  Kassam  (1979).  texture  sites  of the experimental  thick,  overlying  loamy  sand  from  records  and  months  with  area  Columbia  station  campus months  p o t e n t i a l evapotranspirat ion  of Doorenbos  f o r the i r r i g a t i o n  recording  of the relevant  'A' p a n e v a p o r a t i o n  coefficients  Soil  the  of  and only  t o t h e method  Appendix  using  1983).  f o r 20 y e a r s  from  conducted  specifically  procedure  obtained  computed  was  designed  Meteorological located  METHODS  Design  experiment  lateral  irrigation  AND  METHODS  System  field  MATERIALS  were  tables three  was  at least  Pruitt  found 60cm  (1977).  was  Crop  using  part  i n Doorenbos and  representative t o be s a n d y thick  were  and c o e f f i c i e n t s  evaluated  given  were  profile  loam,  (Table I ) .  30cm  31  Table  SAMPLING  SITES  I - Soil  CROP  OR ROOT  Report  AND  S  of the Experimental  0  DEPTH  I  L  DEPTH  R  P  TEXTURE  (cm)  PITS*  A  Cowpea  0 - 3 0  SANDY  30  60  cm  60  I  L  E  AWSC  - 60  LOAMY  - 90  MAX.  APPL. RATE  68.6mm  ( 1.5 i n )  11.4 mm/hr  30.5  SAND C  A W S C  38. 1  LOAM  unguiculata)  F  (mm)  (Vigna B  O  Area  ( 1.2 i n )  LOAMY  0.45 in/hr  • SAND  *  Soil and  3.1.1  samples 60-90  Maximum From  were  were  cm)  taken  from  Crop  Doorenbos  pits  from  three  depths  (0-30,  30-60,  A, B a n d C .  ET E s t i m a t i o n and P r u i t t  By P a n  (1977),  Evaporation the  following  equations  extracted:  ET  0  = Kp  x ETp  [3.1]  and ET(max)  = K x ET  [3.2]  0  where: ET(max)  = reference crop  maximum  e v a p o t r a n s p i r a t i o n , mm/day  32  K  = crop  ET  = reference  0  ETp  = Class  Kp  = pan  Based harvested using  and  Average  (over  Pruitt  mm/day  strong)  of  were  COEFFICIENT (K ) p  i n Table and  relative  70-80%  estimated  days  when II  was  Doorenbos  humidity  and from  i t i s t o be  wind the  obtained a n d Kassam  between  speed  of  quoted  May  112-144  reference  computations.  I I - Computed  PAN  o f 90-100  (1977)  20years)  inclusive,  i n subsequent  Table  lifespan  the tabulation  and  used  rate,  coefficient.  f o r forage,  (very  MONTH  'A' p a n e v a p o r a t i o n  on c o w p e a ' s  August,  km/day  evaporation  Doorenbos  (1979). and  coefficient  E v a p o t r a n s p i r a t ion  CROP COEFFICIENT (K).  Information  REFERENCE EVAPORATION  MEAN E'PORATION  PEAK ET  (ET ),  ET(max),  mm/day  mm/day  day  0  mm/  May  0.8  0.75  3.6  2.5  3.3  June  0.8  0.75  3.5  2.5  3.3  July  0.8  1 .05  3.9  4.  Aug.  0.8  0.95  3.3  3.0  4.  Sept.  0.7  0.90  3.3  3.0  3.6  1  4.6 1  33  3.1.2  Irrigation Cowpea  the  soil  storage  at  (a)  AWSC  temperature  during  =42.85mm/6hrs  into not less  the  than  From  the this  Irrigation Table  based  GWR  the  total  AWSC  Then, t h e  rate  maximum  intake  of  7.1 rate  operate  quite  of  May  10 d a y s  June  10  follows:  set of 6 hours the  irrigation  and i f need be,  entail windy,  mm/hr  I . I = MSWD/Peak E T . a r e as  1983).  A time  i s acceptable.  I I , the intervals  and average  A.R = GWR/Time s e t  s e t would were  application  speed  of the morning  which  Sprinkling  to  an  (BCMAF,  (0.28in/hr).  of time  i s  MSWD/Application  Here,  rate,  hours  MSWD,  =  on wind  season  intended  "  an  (l.35in).  = 42.85mm(1.7in).  hours  interval,  design,  i s necessary.  Requirement,  calm  of  water  Availability  deficit,  x 5 0 % = 34.28mm  period  A.R  assumed.  irrigation  water  i t was  afternoon  desirable.  portion  In t h i s  For  performed:  7.14mm/hr  a longer  that  (2ft).  the available  I).  was  was a s s u m e d  the  o f 60.5cm  50%  the i r r i g a t i o n  because  depth  (Table  application  =  during  Therefore, (d)  80%  Irrigation  evening;  were  = 34.28/0.80 of  system  before  Water  efficiency  chosen  of  soil  Gross  (c)  = 68.58mm  calculations  Efficiency  rooting  (AV. C) r e p r e s e n t s  x Av. C = 68.58  Computations  of the experiment,  coefficient  Maximum  (b)  was  site  c a n be d e p l e t e d  following  AWSC  the  capacity,  coefficient  Design  h a s an e f f e c t i v e  availability  that  System  enchroaching and t h i s  (0.28  the s o i l  in/hr)  was i s  (Table I ) .  34  3.1.3  July  8  August  8  Sprinkler The  pressure  and  (206.9  Standard  days.  Selection  selection  information  "  method the  KPa).  spray  and C o n f i g u r a t i o n was a c o m p r o m i s e  wetted  diameter  A Rainbird Turf  nozzle  was  between at  optimum  Sprinkler,  selected  the  with  design  operating  model the  2800A  following  conf igurat i o n : Application  rate  6.1 mm/hr  Nozzle  2800A-F  Operating Wetted Flow  pressure  3.1.4  206.9  diameter  •  of U n i f o r m i t y ( m a n u f a c t u r e r ' s ) 3.2 - 6.5 km/hr  f t )  84% ( 2 - 5 mph)  Design  4 sprinklers,  each  sprinkling  at  206.9  KPa (30 p s i ) were  the  single  lateral  flow  rate  diameter m/s •  (24  0 . 1 6 1 / s ( 2 . 5 U.S gpm)  range  Lateral  [Full]  KPa (30 p s i ) 7.3 m  rate/nozzle  Coefficient Wind  (24 i n / h r )  a for  (5  pipe  used.  1/s Total  was 0 . 5 6 1 / s ( 8 . 9 2 be  without  delivered flow  ( 2 . 2 3 gpm) flow  gpm).  b y 25.4mm  velocity  into This  internal  exceeding  1.5  ft/s).  38.1mm ease  could  0.14  diameter of handling  (internal)  PVC p i p e  i n the f i e l d .  was  chosen  Figure 1 - Line-Source Sprinkler, System  12.80 UNION  SPRINKLER 3.8 i™  ( 1 . 5 i n . ) PVC PIPE JX  J L  1.52  3.66  LATERAL END PLUG  «_  1.52  «—  2.13  _^  38 mm (I.D)  PRESSURE GAUGE  FLEXIBLE HOSE POINT OF CONNECTION TO MAINLINE OUTLET  L...3.0  3.66  3 -  HOSE ADAPTER  SHUT-OFF  FLOW CONTROL VALVE  VALVE * * UNLESS STATED, ALL DIMENSIONS ARE IN m  PVC PIPE  36  •  sprinkler along had  spacing  the  was  lateral,  a nozzle  throw  3.66m since  -  an  overlap  the identical  o f 3.66m  of  50%  sprinklers  when o p e r a t i n g  a t 206.9  KPa. •  3.1.5  Figure  Mainline 76  mm  University  of  Irrigation  water  482.7  KPa  covering  3.2  British  area. from  the whole  the  lateral  to provide  'continuous  The 7.3 shows  m.  was  a schematic  design.  The  line  plot  and a c r o s s  plot  was  used  a s 3.6m  14.5m  located  and System  line  with  pattern  3  m  used.  from  the  pressure  of mainline  of  hydrant  with  first  spaced  sprinklers  features  described  research  was  similar by F o x  by H u n d t o f t  to  (1973) a n d Wu  (1976). size  the width layout  chosen  of  the  However, left  had a wetted  of an e x p e r i m e n t a l  of s p r i n k l e r s  was  were  the  Layout  suitably  t h e row d i r e c t i o n .  (12ft)  about  on  Characteristics  nozzle  (48ft).  used  farm  network  for irrigation  et a l  sprinkler This  Research  variable design'  and-Hanks  being  farm.  a wetting  further developed  (1974)  accessories.  was d e l i v e r e d a t a maximum  University  System  designed  and other  already  underground  Irrigation single  was  Water the  pipes  Columbia  outlet  Design  The  and  aluminium  Experimental  3.2.1  the l a t e r a l  Design  diameter  experimental  1 shows  line-source was  through  The wetted  only  10.9m  out a t each  diameter  plot.  Figure  sprinkler the centre length  (36ft)  of 2  plot of the  of  of length  end of the l a t e r a l  each was from  37  the  first  lack  of  and  last  sprinkler  The  which  continuously, made  overlap  portable  pattern  sprinklers,  but  Furthermore,  uniform  for  system  produces  along  the  across  using  sprinklers  of  individual  when  effects  water of  the  and  application the  plot.  same  sprinklers  profile  a  length  variable  by  border  ends.  uniformly  triangular-shaped design  account  these  irrigation  is  possible  at  to  plot  and  This  is  configuration.  inherently  operated  in  low  produce  winds  at  the  pressure.  These system  are  the  suitable  characteristics for  the  conduct  that of  a  make  compact  the  irrigation  experiment  in  the  field.  3.2.2  Experimental From  (24ft) of  Fig.2,  wide  the  by  plot  sprinklers  Design  an 10.9m  the  length  than  the  4  plot,  there  were  two  the  or  design given  was in  1983 South  on  procedures a  randomized  Figure  This the  line.  be  ridges  wetted  or  in  this  blocks—  There  were  plot  and  complete  or  5  rows).  by  one  The  and  the  m  width the  designing  for  Within  on  either  each side  comprising  different 4.  7.3  of  study.  plots  remaining block  effect,  diameter  increased  used  the  in  the  irrigation  The  experimental  field  layout  is  3.  field  experiment  University  Campus  in  was,  the  replications  non-irrigated  scheduling  (15  by  could  Layout  plot  long  sprinklers  sprinkler  control  (36ft) governed  more  of  Field  experimental  was  but  and  Road  of  along  was  British  conducted Columbia  South-West  during Plant  Marine  the  Summer  Science  Drive,  of  Field,  Vancouver,  38  British  Columbia.  The planted  soil  type  is  Bose  to  corn  and  documented)  four  years  was,  however,  during  3.3  Spring  Application The  growth  irrigation five  S4  phosphorus  and  to  S5)  that  the  study.  yield  hectare  to  be  matter  (t/ha)  of  the  (cultures base  medium  nothing  of  last  fertilizer  not  experiment.  area  was  a  It  several  being  test  (PI,  P2,  times  grown.  75  W1,  W2  P3,  P4  Thus,  replicated of  crop and and  techniques  investigated.  production areal  of  moistened  reached of  and  there  twice  to  three  W3)  under  P5)  when  (S1,  and,  experimental  with  the  [L.] on  Walp.  the  matter were the  their  S2,  S3,  were  75  i t follows units  each  ) was  basis  of  produced  harvested late  boot  selected metric  was  used  when stage  tons as  the  for  the more  immediately  inflorescences.  Maintenance  blackeyed  nitrogen-fixing from  dry  plants  appearance  variety  of  whole  scheduling  unguiculata  Establishment  were  levels  each  The  preceding  seeds  this  (hereafter denoted  consisted  individuals  White  of  was  blocks.  indicator.  Crop  site  dose  of  the  response  irrigation  advanced  3.3.1  when  The  and  start  even  yield  Vigna  Dry  the  harrow  levels  five  (  (name  to  fertilizer  two  Cowpea  per  and  experiment in  loam.  Treatments  combinations  appearing  the  of  were  treatment  before  Summer  water  subjected  fertilized  habitual and  sandy  pea  clean  seeds  water  bacteria,  Nitragin  and,  were  Nitragin  Rhizobium  Company,  planted.  spp,  The  innoculant in a  Clearwater,  peat-  Florida  39  33516,  USA)  thoroughly analysis matter  of  Seeds  seed  were  Seeds  per  the  innoculant.  from  total  nitrogen  on  June  no  experimental when  and  after  area.  A  the second  days  unit,  total  of  stand  had  failed  180  organic was  a  seeds  Before  stands  spacing  Depth  two  were  obtained. There  were  per r e p l i c a t e ,  stands  in  o r one  or died  the  ( i n the  off  of  planting,  was  planting.  2 plants  t o emerge  and  viability  1800  soil  treatment  Within-row  thinning.  t o seven  were  problems].  t h e row,  95%  a  seed  (2ft)apart.  ran and about  per experimental  per p l o t  on  seeds  evidently high  1983.  60cm  until  [Preliminary  this  20th,  were  requiring  five  showed but  1.27-2.54cm  was  shaken  nitrogen-induced  t h e rows  was  test  the s i t e  against  hole  stands  case,  with  planted  germinated  stands  carefully  ( 1 f t ) while  germination  12  and  placement  placed  and  samples  insurance  30cm  added  coated  content  further  was  was  360  entire latter  even  after  replant ing). Fertilizer was  applied  two  days  after  manual  and  performed  90  percent  emergence  recorded. Weed  20th,  was  control  July  symptom  31st and August  was  undertaken.  was  observed  25th,  hence  no  three  times  1983.  No  pest  control  in that  or  - on  July  disease  direction  was  40 Figure 2 - Schematic of a Test Plot 7.31 m •  >  3.66m nozzle throw ^  at  206.S KPa  3.66 m  D i r e c t i o n of increase i n s o i l WI  c  W2  moistui -e l e v e l s W3  W3  WI  MAIN SHUT-OFF VALVE —  IRRIGATION LINE SOURCE  MAIN  W2  L I N E  H Y D R A N T  FARM IRRIGATION WATER OUTLET SOURCE  Figure 3 - Experimental Design and System Layout i n the F i e l d TO i—i  cn O  cr  i-i  o  o  m  M A IN  s:  LINE  0  m  FLEXIBLE HOSE  ?3  _ » j L , — 0.60m foot path round each p l o t  r~  >  —1  -o >—(  O a  rn as I—* VO  m  11  50  VD  |  ROW JL  7.31 m  38.41 m  DIRECTION  1r •  42  3.3.2  Irrigation Water  source  treatments  sprinkler  This  system  the  lateral  in  (Hanks line  uniformly  operated This  Water  number  were  imposed  by p l a c i n g  system  designed,  e_t a l ,  1976),  decreasing  amounts  mornings  applied  with  or late  application pattern  of i r r i g a t i o n  water  the  i n the middle  i n the experimental  in early  water  Treatments  water  area  line-  of each  plot.  uniformly  down  and c o n t i n u o u s l y ,  distance  evenings  provided  single  from  the line  under  high  levels  to  select  outlay  of  the  but  calm  winds.  flexibility within  when  i nt h e  practical  limits. Figure sampling before three  4  shows  legend and  for  after  were  1 m  2 m  (3.5ft),  either  side  distribution the  A using not  (6.5ft)  o f t h e same major  limitation  s p r i n k l e r s was a l s o  be r a n d o m i z e d .  characteristic Since achieved  only  will  W1  o r W2  the  exhibited  be d i s c u s s e d  calm  W2(106.8mm)  and  located  of  about  away  uniform  from water  perfectly parallel during  to  low wind  to  give  an  water.  continuously here:  variable  the water  liability  of  levels this  design could design  later.  uniformity wind  The  was a s s u m e d  of i r r i g a t i o n of  event.  respectively  Because  The s t a t i s t i c a l  reasonable under  (10ft)  determinations  sites  sprinkler operation  the line depth  sampling  at a distance  assuming  along  soil  and the s o i l  a rainfall  W1(3l.2mm),  lateral.  the plot  lateral  moisture  and a f t e r  and 3 m  the  and  soil  levels,  essentially,  along  sampling  estimate  water  of  lateral,  speed,  gravimetric irrigation  irrigation  W3(l69.8mm)  an  along  conditions  the (Hanks  line  could  et a l ,  be  1976),  43  sprinkling morning and  in  except  coupled  intervals this was  with  high  row of  use site.  rest,  of  operation,  and  areas  determined  Applied  moisture  samplings.  of  depletion  gravimetric  by  water  in Appendix  University  are  B.  crop  between  as  irrigating wind  speed  was  rows) left  compared  on out  with  experience)  well  as  at  plant  4. each  catch  irrigations and  and  Crop soil cans  r e c o r d was weather  pre-  to  sprinkler  in Figure  Columbia between  in  uniquely.  as  Precipitation  British  difference  rows  measured  applied  machinery  (from  hydrologic balance was  by  them  lateral  illustrated  hours  evening.  stopping  harvests  6  the  because:  over  two  of  was  zero,  position  and  of  set  times  field  measurements  for plant  determinations was  (across  influence  at  at  hours  was  in, the  lateral  d i s t u r b e d these  used  and  continued  movement  early  time  runoff  afternoon  be  the  irrigation  keep  starting  constant or  to  in  in which  that  sprinkler  exceptional  done  S2)  each  experimental  the  reported the  the  of  damaged  to  plants  (i)  The  (or  fact  i t had  of  from  (ii)  water  the  2  was  s t r e t c h e d to  that  side  entirely  for Plot  often  One either  experiment  (intermittently)  plot so  this  water  sampling and  obtained  station. was  soil  is from Soil  measured  by  post-irrigation  44  Seasonal determined  and  using  shorter  the  time  periods  of  water  use  were  equation:  E T = I R R + P + D + A S - Q  [3.3]  where: ET  = water  use  (eg  IRR=  irrigation  P  =  precipitation  D  =  drainage  AS  = change  seasonal,  water  in  m o n t h l y ) , mm  applied  stored  soil  moisture  for  the  period  considered Q  In  =  the  surface  application  following 1.  there value  were  water  passed  Drainage,  which  is  contribution  when  taken  there  as  zero  irrigating  the  percolation  was  Water  and  balancing  this  use  irrigation these  excluded through  balance  from  root  a  percolation  either zone  —  equation,  the  i.e.,  all  value  when  zone  positive  groundwater  deep  under  runoff  the  assumes  is  root  moisture  made:  A l l precipitation  2.  different  of  assumptions  rainfall  was  runoff.  and  a  from  negative IRR  circumstance.  to  field  or  But  capacity,  P, in  deep  unavoidable.  hence  water  scheduling  hydrologic  inputs.  use  efficiency  methods  were  under  determined  the by  45  Figure 4 - Experimental Units and S o i l Sampling S i t e s JO "  J L  o o o  0.60 m  r  -O—G  WO  W2  WQ_  Wl  QROW ROW O—Gr  -&-Q—O  P5 O  PI  E' CTl o i—i  OO E o CNJ• CC CO ro  P3  (> o o o  O OiO  r-  o-&-  ROW  Q 0| O O o d> o o  P4  O  +->  o 4t— o_ J OCQ ZD OO  O i O Q O O O (I  C  £ CO Ol S-  +->  • -4-> SO) 4— «—I  P2  W3  WO  WO  W2  Wl  2.25 m 3.66 m  LEGEND:  3.05 m  LINE SOURCE SPRINKLER  A r b i t r a r i l y randomized f e r t i l i z e r P l e v e l s . F i e l d machinery row o r i e n t a t i o n  -X—X  W3  W3  WO x * WO 0 0 0 0 o 0 o o  A l l s o i l samples taken along t h i s l i n e a f t e r an i r r i g a t i o n were assumed to have received the same amount of water. Disturbed rows, not sampled for analysis An experimental u n i t with 12 plant stands, 2 p l a n t s / h o l e  46  3.3.3  Phosphorus Five  Fertilizer  levels  superphosphate equivalent  ( 0 , 50, (18%  5cm  was  manually.  The  ring  and  The  P  and  in effect,  latter on  and  4 shows Each ran  0,  and  80  kg/ha)  ingredient)  6.2,  7.4,  dug  applied row  8.6  appropriate  P5,  back  an  level  were and  P 0 2  of  5  applied. 9.8  single This  g/plant  with  of  top  order,  was  stand  away  Going a  from  fertilizer  henceforth were  by  the  hole  about  the crop  stand,  was  applied  was  referred  randomized to  the  randomization  the length  1983.  in  soil.  angles  fertilizer  treatments  25th,  application,  2.54cm  amount  arbitrary  across  the f e r t i l i z e r  and  at right  of  June  treatments,  in that  were  on  fertilizer  round  fertilizer  P3,  plot.  P4  of  covered  P2,  Figure  was  practice  deep  the  70  (Table I I I ) .  Fertilizer standard  60,  active  to applying  respectively  Treatments  applied  of the p l o t .  i s as g i v e n  along  water  i n one on  to as the  Further  plot  variable.  replicate  three  P1,  rows —  of a the  information  in Table I I I .  47  Table  FERTILIZER  FERT.  LEVEL  III - F e r t i l i z e r  RATE ACTUAL  kg/ha  18%  utilized The  will  et  (g)  0  0  0 6.2  P3  60  333 . 3  266.7  7.4  P4  70  388.9  311.1  8.6  P5  80  444 . 4  355.6  9.8  Section  amount  Scheduling 3.1,  the  that  to  point,  derive  kg  with  moisture.  soil  the  actual  ET  data  the  latter  maximum  and will  were  experienced climatic  Actual  moisture  e t a l , 1981  crop  irrigation  varies  at approximately  Stegman  and  ET  soil  available  and  the a c t u a l  p o s s i b l e ET and  11.6  ingredient  soil, (ET)  3.1.2  between  =  Techniques  climatic,  in subsection  used  a . i . = active  evapotranspirat ion  a l , 1970;  Beyond  (g)  222.2  proceed of  stand  277 .8  development  half  SUBPLOT p e r  FERT  50  t h e maximum  crop  of  P2  relationship  and  Wt  0  Irrigation  estimate  PER  Wt  P1  *  In  FERT.  (kg/ha)  Total  3.3.4  of  FERT.  a . i. *  -  Wt  data  has  was  to  in turn  intervals. by  the  crop  conditions,  evapotranspirat ion  rate been  E n g l i s h and fall  used  until  perhaps  depleted  (Jensen  Nuss,  progressively  1982). farther  48  behind the  t h e maximum  irrigation  actual  rate.  schedules  coefficient)  after  available  moisture  On  the basis  moisture minimum  assumed  occurs  approaches  depletion  time will  this  M  50%  (availability  moisture  linearly  has  from  1.0  but  widely  relationship  a  selected  interval  schedules  time  i n which  throughout  each  that  by  50% b e t w e e n  than  AWSC  evapotranspiration produced  these  until  =  soil  time s e t ,  established.  of several  July  specifications  set  days  50%  ET*  so t h a t t h e  depletion  ( T  5  0  )  any  ET  were  during  intervals  derived  were  in  not  uniformly with  be  a period  for  full  o f maximum irrigation  = 8 days  irrigation the  the  depleted  the cropping  August  from  assuming  conjunction  would  design  following  h r s . , and  in  zone  = 8 days,  The  6  deficits  month,  the  moisture.  of  irrigations  demand,  10 d a y s .  soil  i n the root  irrigation  10 d a y s ,  September  to 0 as  used  between  E T a n d A v . C was  the i n i t i a l  specification more  been  [3.4]  denotes  0  distributed  system:  until  of  possible  0  irrigation  their  maximum  soil  decline  the r a t i o  be  Using  =  1.0  that  specifying  = M /(2ET*)  5 0  where  June  equal  for a period  or i r r i g a t i o n  was  in  exhaustion.  a  interval,  used  to  simplified  model,  constant  study  available  i t would  of  irrigation  elapsed  (ET*) w i l l  which  this  (ET )  o f t h e maximum  depleted  T  in  evapotranspirat ion  evapotranspiration  was  The key a s s u m p t i o n  months: and  schedules and  full  irrigation  49  [S1]..  This  was  (Figure  3).  This  before  planting  the c o n t r o l . plot to  was  establishment.  irrigation  water  the  rainfall  irrigated  ensure  seedling  b u t no a t t e m p t  that  fell  on  schedule  s p e c i f i e d f o r the  configuration  based  on s t a n d a r d  Section and  inbetween) days  in  10 d a y s  [S3]..  the  no f u r t h e r  that  The  8 days  system  was  described  in  FC  event  rainfall and  8  moist  and  was a p p l i e d .  basis  interval  rains  quite  two  with  the F a l l  water  i n S 2 , i f no r a i n f a l l  to  in July,  was  the  irrigation  was n o  soil  of  i t i s  sprinkling at a  i n September,  the  enumerated  system.  minimum  i n June,  On  irrigation  set per  there  This  irrigations.  plot.  I n summary,  water",  i n September.  deficit  as  (whenever  first  control  irrigation  time  irrigated  i s  to  the  (or 2 f t ) of s o i l  Early  further  irrigation  above.  (0.28in/hr).  stabilized,  was  again  no  and t h e key a s s u m p t i o n s  of i r r i g a t i o n  August.  therefore, plot  was  full  chapter,  irrigations  was  procedures  t o w e t 60cm  (1.7in)  made  good  a s any o t h e r  this  the f u l l  design  t o mention  o f 7.lmm/hr  between  had  of  of t h i s  6 hours,  42.85mm rate  3.1  II,  relationships discussed  helpful was  Plot  was  I  capacity  and  received  i t , just  Alloted  to field  germination It  [S2]..  The  I t was a l l o t e d P l o t  In f a c t ,  no  high-frequency of  intervals  occurred  within  50  any  particular  irrigations),  interval t h e same  ( o r between amount  applied  a s i n S2 b u t i n  amounts  (14.3mm  rainfall,  s a y , soon  of  42.85mm,  2/3  o f 42.85mm  been  saved  that  42.85mm  hours ran  each).  per  to  carry  applying  and  of water  applied  was  III.  This  IV,  Plot  the  product  time  broken basis  The  for from  into  irrigated  in  i t s dry matter  three  to  have  6  man-  schedule  was  1/3 o f 5 0 %  on t h e l i f e s p a n  the type crop,  yield  of plant  Cowpea,  was  and a c c o r d i n g l y ,  harvest  vegetative  interval,  procedure.  based  The t e s t  third  'Stage-of-Growth'  particular,  planting  one  t h e whole o f  16.5% =  this  enough  (90  stages,  days),  strictly  was  on t h e  of age: 1st  stage  = emergence  2nd  stage  = 31-60 d a y s ;  3rd  stage  = 61-90 d a y s .  plot  was  appropriate 5th  and  was  was  requiring  called  t o be h a r v e s t e d .  harvested the  method,  crop  i n which  been  smaller  would  irrigation  under  also  there  the f i r s t  T e c h n i c a l l y , only  [S4]..  and  man-hours  t o S2  was a l l o w e d  of  4  have  t o t h e next  i n comparison  AWSC d e p l e t i o n  scheduling  when  the crop  of water  would  separate  However,  irrigation.  on P l o t  of water  three  after  a n y two s u c c e s s i v e  August.  irrigated  lateral The  t o 30  to  overlapping third  days;  field  capacity  on t h e 4 t h J u l y  irrigation  by  a n d on  was s c h e d u l e d f o r  51  September not  but f o rthe reason  This  was  schedule.  each  In  was  at half  month  required  the  It  irrigated  and  only  S2 i r r i g a t i o n  All  plots  were  water  B.  ANALYTICAL  PROCEDURES  3.4  The S o i l  Soil site  after  Plot  of  in  or  became  before  1/2  was  S2 f o r  the gross  to deplete  o r 2 5 % o f AWSC  and  and  set i.e., 3  was a l l o w e d  irrigation  V  water  hours. only  1/2  of  50%  necessary.  planting.  scheduling  Therefore,  procedures  started  Analyses samples  were  immediately  the crop  depths  time  treatments  emergence.  Soil  a t each  irrigated  seedling  the  was  irrigation  interval  half  depth  t h e next  irrigation  on  one  the crop  before  3.4.1  S2, t h i s  high-frequency  conducted  was a p p l i e d  essence,  2nd  the calculated  AWSC  after  under  implemented.  [S5]..  of  stated  (Table pH  taken  before  (soil  three  Samples  The f o l l o w i n g  Soil  in calcium  i i .  Available  K, Mg a n d C a b y M o r g a n ' s  i i i .  Available  P by Bray-1  iv.  Organic  content  chloride  began  were  analyses  i.  matter  representative pits at  the experiment  was h a r v e s t e d . I).  from  and  collected  were  immediately from  performed:  solution) extraction  method by W a l k l e y - B l a c k  method  method  three  52  v. vi. vii.  Available Sulphate-S Soil  texture.  These the  nitrate-N  are  standard  procedures  adopted  Lavkulich  (1983).  3.4.2  Moisture  Soil Soil  layers  following  was —  the  could  be  soil  made  Determinations  sampling  determinations profile  laboratory  for  to  During  for  0-30cm  and  and  Black  references  to  e_t a l , ( 1 9 6 5 )  and  Experiment  gravimetric  undertaken top  tests  moisture  each  sampling  30-60cm  by  content  site  augering  for  two  on  the  bases:  •  before  every  irrigation  •  4-5  hours  •  2-3  days  after  irrigating  •  2-3  days  after  every  after  irrigating  Plots Plots  heavy  III II  and  and  V  IV  rainfall.  Note: Plots  II  and  therefore, distribution  i t  .IV was  i n the  were  irrigated  necessary profile  for a  to  to  field  capacity,  allow  period  of  moisture 2-3  days.  53  3.5  The  3.5.1  Crop  Crop  Growth  Indicators  The  plant  performance  assessed  using  three  measurements  were  beginning  week  one  a  seedling  Number  of  nodes  3.  Number  of  trifoliates  that to  "source"  cowpea  matures  in  is  subsequently  before  explanation  growth  the  of  the  the  they  of  seven  r e p r e s e n t a t i v e of  weeks  to  leaf as  the  f l o w e r i n g and  yield from  crop  at  data the  in each  matter  (1976),  the  number  source  as  seed  number  nodes.  various  on  area  "sink"  total  these  experimental  reported  or  to  (1977)  dry  obtained a  easy  surface  a  Kassam  on  others  Sinha  accumulation  measured an  many  relatively  plant)  r e t a i n e d at  the  of  high  dependent  were  was  a  of  originates  values  were  according  and  of  out  Furthermore,  of  ultimate  indicators  recorded  chosen  sites  onset  performances  These  mean  following  plant.  per  largely  treatments  cycle.  per  counts  produced  for  growth  plants  basis  was  emergence:  realisation  and  pods  looking  for  equipment.  is vital;  produced  physiological  weekly  were  to  cowpea  of  The  growth  plant  mobilised  nodes  combination  of  indicators.  because,  little  the  be  per  indices  trifoliate  to  crop  yield  for  requiring  (related  stages  height  growth  explained  its  after  on  2.  measure,  an  taken  Plant  recommended  different  growth  1.  These  the  at  of of  Thus,  from of  a  these  stages  of  three  healthy-  unit.  Only  case.  the  54  3.5.2  Crop The  Yield crop  was  20th,  1983.  September taken. plot  However,  to give  achieved was  by  had  matter  3.5.3  the  were  plants  been  dry  were  uprooted  about  the  and the e x t e n t  production plant  a t random  actual  in a  before.  i n the f i e l d  was  from  each  when  field The  before  on  part  rooting  of n o d u l a t i o n  bacteria  cultivated fresh  matter  above-ground  non-specific  weighed  Nutrient  depth cowpea  where  the  areal  drying  parts  for  dry  cowpea  —  harvested  had a l r e a d y most  1973),  developed  agree  that  prior  from  photosynthesizing  to  nodules fruit  wall.  prior  uptake  of  nutrient.  applied  subsection  2.5.2  (3  to  leaves  above)  were  well  Hence,  Most  in  Nine  especially from  gives  preserved  plant  for  Sinha leaves i s by  the  still  terminal  a good  index  leaves  of per  collected  foliar  on  terminal  of  terminal each  and  filling  collection  time,  workers  cowpea  Grain  as  flowering  from  a t which  Shanthakumari  leaves,  as  immediately  unit  buds.  flowering.  these  leaves  experimental  flower  stage  photosynthesis  of a s s i m i l a t e s from and  a t the boot  a u t h o r i t a t i v e being  immediately  transfer ones,  was  the  and  ceases  Uptake  crop  stands  (1972  with  the  idea  crop  for  measurement.  The some  some  never  harvested  Only  a general  innoculated  crop  harvested  in  (chemical)  analyses. The samples  method f o r N,  Digestion  P,  of K,  for foliage  preparation C a a n d Mg  was  (Lavkulich,  and t o t a l by t h e 1983).  analyses Parkinson  of the and  leaf Allen  5 5  3 . 5 . 4  Statistical A  Comparison  statistical  effects  and  phosphorus  interactions fertilizer  produced  by  presented  i n the  chapter determine  analysis  the  IV. yield  Phosphate statistical  and  crop. form  of  of was of  Results performed irrigation  irrigation The  results  'Analysis  of  levels  of  differences  between  any  analysis.  data  was  also  determine  amount  the  of on  of  analysis  this  5 two  and  1% w e r e  treatment  subjected  dry  (ANOVA)  to  main  water,  schedules  Variance'  Significance  uptake  to  matter are  table  in  used  to  means. a  similar  56  IV.  4 .1 Soil  R E S U L T S AND  DISCUSSION  Properties  Results experimental  of  analyses  site  prior  soil  to planting  a r e shown  is slightly  The  area  soil  p r o p e r t i e s a r e as given  i n t h e same  It  determine  i s well-drained,  was  properties  30cm  necessary  characteristic  of top s o i l ,  very  SAMPLE PH  (cm).  and  Figure curve  slope  5  on  CONTENT  AVAILABLE  layer  was  (%)  Other  pertinent  retention  K  retention  to follow  figure.  on M o r g a n  IN  Soil  SOIL  Sulfate-S  TEXTURE  ppm  0-30  5.9  1.35  75  12  14  nd  SL  30-60  5.5  0.88  16  12  12  nd  LS  60-90  5.3  0.75  25  nd  nd  nd  SL  nd  = not detected  pH  = s o i l , i n 0.01N  Results  represent  in soil Calcium  sample; chloride  the average  values  (1:1); for 3  soil  (approximately  found  t h e same  P  The  p r e s e n t a t i o n of the  NUTRIENTS  Nitrate~N  IV.  analysed.  moisture  Analyses R e s u l t s Based T e s t i n g System  MATTER  the  depth  of the moisture  B)  from  table. the  The p l o t  shown  i n Table  o f 3-5%.  i s a  (Curve  taken  profile  of t h e plow  A).  i s also  IV - S o i l  ORG.  DEPTH  on a  of the s u b s o i l  closely  Table  Curve  t o t h e 90cm  to  of the s o i l .  characteristic one  down  samples  soil  moisture  acidic  of  SL =  sandy  loam  LS  loamy  sand  =  profiles.  this  57  It  c a n be  capacity of  soil  1500  seen  (suction  or  15 b a r s )  curve  ( d e r i v e d from  test)  i s the fact  a  series  was  a  of  the  i s 12.1%.  be  to yield  effect  and d r y i n g  practice.  The d r y bulk  density  point  obvious  layer  of  during  irrigation  overlook  approximations been  was  test  conversions  d e p l e t i o n thus,  of the s o i l  this  the laboratory  have  of  retention  Subsequent  are  always  field  (suction  moisture  cycles,  water  the  limitation  situation  then,  as they  that  bar) of the t o p  wilting  exercise.  available  with  5  laboratory  field  and a t best,  contained  o r 0.3  One  of a  whereas  of wetting  curve  Figure  the permanent  results  that  of  30 K P a  straight-forward drying  hysteresis must  A  of about  i s 30.7% w h i l e  KPa  is  i n curve  in  found  which  irrigation t o be  1.01  g/cc. • Soil  test  experimental reflects noted  quasi-pot same are  was  for  a r e shown  the  fertilizer  from  these  Analysis  reported  available in Table  of phosphorus  experiment.  data. also  run  the rate  that  sampling  values  P V.  at  applied.  band-applied  highly concentrated Figure f o r K,  (Table V I ) .  6 i s a C a , Mg  end  of  The a v a i l a b i l i t y  fertilizer  was  the  further  sites  It  and —  trend  may  be  subsequent a  sort  illustration  and organic  the  matter  of  of the content  Figure 5 - Moisture Retention Curves of Experimental Soil 60^,  0  -j-:  ,  !  ,  ,  0  2  4  .6  8  .—,  10  SUCTION (bars)  ,  ,  12  14  .  ,  16  59  Table  V -- M e a n  Extractable. (Available)  FERTILIZER  P  L  P  in  0  soil  i n  T  ppm  S  TREATMENTS  SI  S2  S3  S4  S5  PI  64  98  36  72  40  P2  1 22  1 32  1 34  1 74  1 56  P3  1 24  151  1 77  1 20  1 78  P4  1 60  232  228  1 86  206  P5  186  186  204  1 66  238  4 .2  Crop  Development  Weekly counts  measurements  and  emergence  number  were  trifoliate emergence  unfertilized plots.  Cold  suspected. by  the  time, the  day  the  nodes  was  there  also  wettest  were  temperatures  temperatures had  after  plants  was of  no  this  were  a  the 5-7  a  elongation, as  a l l  from  plots,  fourth per  the  week  symptom stable  15  deg.  five  combination  on  fertilized  deficiency became weeks, or  Plants  (S3W3) w e r e  of  seedling  However,  Celsius  themselves.  after  number  than  deficiency after  days  from  plant.  nitrogen  nitrogen  trifoliate  seven  l i g h t e r green  and/or  established  treatment  stem  plant  3-5  plots,  That  per For  of  disappearance  plants  under  was  of  out.  number  soil  rate  nodes  carried  leaves and  of  of  most  were evident  at  which  over  and  growing stunted  60  throughout  these  frequently The  irrigated  maximum  30cm,  about  plants  exhibited  of  was  mechanical root  by  crop  group  4.3  of  was  on  planting. root  the  control  and  under  this  i n view plot.  less  not a  restricting  of  crop  b u t i t was factor  phosphorus . f e r t i l i z e r  i t sroots  below  as  i t was  30cm  (control) because the  of the o c c a s i o n a l l y  The c o m b i n a t i o n  rooting  some  to explore  A maximum  this  site.  was  perhaps,  treatment  from  this  pits  Non-irrigated  elongation,  of t h i s  the shallow  to extend  of s o i l  root  depth  obvious to of  that  vertical irrigation  might  have  not necessary f o r depth  in  this  of p l o t s .  Crop  Yield  Response  Dry  matter  yields  seasonal  irrigation VIII  top s o i l  expected  to  to  in profile  f o r moisture,  application  contributed the  after  layer  impedance  band  observed  the plants  development  and  depth  the greatest  profile  60cm  compared  plots.  days  moisture-deficient of  weeks  root  90  the attempt  deeper  7  performed The  irrigation  scheduling  contains  in relation  the  f o r the  techniques result  test  significant.  This,  reasons  and T o r r i e ,  successful  water,  phosphorus  a r e as  in  fertilizer  Table  of the a n a l y s i s  combinations  VII.  of variance  and Table  (ANOVA)  yield.  statistical  (Steel  to the d i f f e r e n t  i n reducing  in  revealed  that  statistical 1983):  error  (a)  variance  block terms, the  by  effect may  was  be d u e  experiment  the grouping  t o two  was of  not  not  ure 6 — Extractable P in Soi  3CH  P1  1  1  — I  P2 P3 P4 APPLIED PHOSPHATE (kg/ha)  r  P5  Table  VI  (at  F  R  E  T  TEST  PHOSPHORUS POTASSIUM S1  MAGNESIUM CALCIUM ORG.  MATTER  P  S2  52 . 0  of  I  of  Soil  experimental  I  Z  P2 B  76 . 0  Chemical  Analyses  run)  E  R  L  B  1 2 8 .. 0  1 16 . 0  A  96 .0  V  L  E  P4  P3  A  E  P5  B  A  B  1 5 2 .. 0  108 . 0  212,,0  A  B  212 .0  160..0  0 . 17  0. 20  0 . 16  0 . 22  0 . 16  0 . . 19  0 . 34  0 . . 12  0 .56  0 . . 19  1 .4 1  1 . 4G  1 .. 7 7  1 . 46  1 .4 1  1 .. 4 6  1 . 56  1 .. 1 6  1 .. 5 6  1 .. 4 6  1G . 6 4  17 . 2 4  19 . 6 6  16 . 9 4  16.. 6 4  19 . 0 6  1 7 .. 8 5  1 4 ,. 8 2  1 8 .. 7 6  1 8 .. 4 5  2 . 5  2 . 4  2 .. 1  2 .6  2 .. 1  2 ,, 8  1 .. 9  2 ,. 3  2 .. 7  2 .. 6  1G0. 0  36 . 0  160. 0  104 . 0  1 5 2 .. 0  150..0  2 6 8 .. 0  1 9 6 ,. 0  1 5 6 .. 0  1 7 6 .. 0  K  0 . 23  0. 22  0. 20  0 . 20  0.. 22  0 . . 19  0 , 17  0,. 20  0 . . 14  0 . . 14  Mg  1 . G1  1 . 36  1 .. 5 1  1. 4 1  1 .. 2 6  1 .. 7 1  1 .. 5 1  1 ,. 4 1  1 .. 1 1  1 .. 2 6  Ca  17 . 5 5  16 . 6 4  1 7 .. 2 4  18 . 4 5  16 . 6 4  1 8 ,, 4 5  1 9 .. 0 6  1 6 ,. 6 4  1 4 .. 2 2  1 7 .. 2 4  2 . 4  2 .4  1 .. 9  1 .9  2 .. 5  2 .. 5  2 . 7  2 ,. 5  2 . 1  2 .. 7  20. 0  52 . 0  1 2 8 .. 0  140 .0  172 .0  1 8 1 ,, 0  2 3 2 .. 0  2 2 4 ,. 0  208 .0  200..0  0 .M  P  S3  /! k  end  I  P1 PLOT  Results  K  0 . 16  0 . 14  0.. 1 1  0 . 19  0 . 17  0.. 23  0 . 20  0,. 22  0 . 12  0.. 23  Mg  1 . 36  1 . 51  1 ,, 1 6  1 .71  1 . 36  1 .. 3 6  1 . 3G  1 ., 3 6  1 .01  1 . 56  Ca  15 . 7 3  17 . 5 5  1 5 .. 7 3  16 . 0 3  16 . 6 4  1 4 .. 5 2  16 . 0 3  1 6 ,. 9 4  12 . 10  18 . 4 5  2 .0  1 .9  2 . 1  2 . 4  1 . 9  2 ,, 1  2 . 2  2 ,. 2  1 .8  2 .. 2  0 .M  S  Table P  S4  continued 64 .0  204 .0  80 .0  144 . 0  140 .0  100 .0  228 .0  144 . 0  136 .0  196 .0  K  0 . 16  0.. 2 0  0 . 19  0 .20  0 . . 14  0 , . 14  0 . 14  0 . . 14  0 . . 17  0 . . 19  Mg  1 .06  1 .. 1 1  1 .51  1 .. 2 1  1 .. 0 6  0..96  1 .01  1 .. 2 1  1 .. 4 6  1 . 36  Ca  13 . 0 1  1 5 .. 13  16 . 0 3  18 . 4 5  13,, 9 2  1 3 .. 3 1  15 . 13  1 5 .. 13  1 7 .. 2 4  16.. 6 4  2 .3  2 ,. 1  2 .4  2 .4  2 .. 5  2..6  1 .9  2 .6  2 . 1  2 . 7  1 6 .. 0  6 4 .. 0  176..0  136..0  2 2 8 ,, 0  1 2 8 .. 0  196 . 0  216..0  2 2 4 .. 0  2 5 2 .. 0  O.M  P  S5  VI  K  0 . . 19  0 , . 19  0 . . 19  0 . . 16  0 . , 19  0.. 22  0 . 22  0 . . 16  0.. 22  0 . . 16  Mg  1 . 1 1  1 .. 1 1  1 .21  1 .. 0 1  0 . .91  1 ,. 0 1  1 .21  1 .21  1 .. 3 6  1 .. 1 1  Ca O.M  14 . 8 2  1 4 .. 8 2  15 . 13  1 5 .. 4 3  12 . 71  1 8 .. 1 5  16 . 0 3  1 6 .. 3 4  1 6 .. 9 4  1 5 .. 4 3  2 ,. 1  1 .. 9  1 ., 9  2 .. 0  2 . 5  2 . 6  2 .. 1  2 .. 6  2 . 2  2 .. 2  NB : *  P i n  ppm  *  Ca,  *  Organic  matter,  *  A  are  K  and  and  B  Mg  in  meq/100g O.M,  in  r e p l i c a t e s  s o i l % (blocks)  Table  S1  VII  W1  W3  W2  p 1  1 1 .. 8  1 1 .6  1 1 ..8  13.. 5  12 . 2  9 . 7  P2  ' 1 2 .. 3  1 2 .. 2  1 1.7  14 . 9  13 . 7  P3  13 . 6  1 4 .. 2  14 . 2  18 : 1  P4  1 4 .. 8  1 5 .. 2  1 5 .. 2  P5  1 5 .. 8  1 6 .. 2  6 8 .. 3  6 9 .. 4  Matter  y i e l d  (metric  W1  W3  W2  9 . 3  10.3  1 3 .. 1  1 1 .. 3  11 . 3  10 . 9  1 1. 9  13.6  15 . 8  1 1 .. 7  16 . 2  1 1. 3  16 . 3  15.1  20 . 5  19 . 6  17 . 1  1 1.8  14 . 4  16.8  15 . 6  19 . 8  18 . 0  12 . 6  13 . 5  68 . 6  89 .6  77 . 2  56 . 3  65 .4  --  ... --- • 2 2 3 . 4 - '  W1  --  74 . 5  68 . 8  S  =  IRRIGATION  SCHEDULE  W  =  IRRIGATION  WATER  P  =  PHOSPHORUS  FERTILIZER  TREATMENT  W3  tons/ha)  S4  W2  - 2 0 6 ., 4 -  MEAN  Dry  S3  W2  SUM  Mean  S2  W3  SUM  -  S5 W3  W2  W1  9..6  1 5 .. 7  14 . 4  1 4 .. 0  179 . 5  1 1. 3  1 1. 3  19 . 4  20..9  16 . 9  208 .6  14 . 4  13 . 9  14 . 7  23 .9  2 3 .. 8  18 . 7  249 .0  22 . 1  1 6 .. 1  14 . 3  14 . 6  2 6 .. 1  2 3 .. 6  22 . 3  264 . 3  17.9  22 .5  15 . 2  15 . 0  14 . 0  24 . 3  2 3 .. 4  18 . 1  261 . 9  73 . 7  94 .0  68 . 7  65 .8  64 . 2  109 . 3  1 0 6 .. 1  90 .0  --- ---  198 . 7 -  --• --- - 2 3 3 . 1 77.7  --  68 . 2  W1  SUM  --  --- - 3 0 0 . 5 100 . 2  Table  SOURCE OF  VIII  -  Analysis  DEGREE OF FREEDOM  Variance  SUM OF  VARIATION  BLOCK  of  (ANOVA)  of  Dry  VARIANCE  matter  F  SQUARES  % CONTRIBUTION  TEST  r-1  = 1  81 .4  81 . 4  Yield  BY  S.S  0 . 84 n . s  s.  SCHEDULE  s-1  4  120653 .2  30163 . 3  3 1 2 .. 5 9  **  40 .8  w,  IRRIGATION  w-1  2  3 4 8 5 .6  1742 .8  18 . 0 6  **  1 .. 2  p,  PHOSPHORUS  p-1  4  9 1 130 .9  22782 .7  2 3 6 .. 0 9  **  30 . 8  67 . 4 0  **  17 . 6  SW  (s-1)(w-1)  =  8  5 2 0 5 8 .6  6507 . 3  PW  (p-1)(w-1)  =  8  9 0 1 ..4  1 1 2 .. 7  1 .2 0 n . s  0 .. 3  SP  (s-1)(p-1)  =  16  11712 .6  732 .0  7 .. 59 * *  4 .. 0  SWP  (s-1)(w-1)(p- 1 )  =32  8 2 4 8 .. 5  257 .8  2 .. 6 7  **  2 ..8  9 6 .. 5  ERROR  (swp-1)(r-1)  =  74  7 1 3 9 ..0  TOTAL  (spwr-1)  =  149  2 9 5 4 1 0 . .9  Analysis  of  variance  n.s  = not  significant  **  = significant  at  on  raw at  data  5%  1% l e v e l  of  level .  yield  from  2  replicates  66  individual  units  homogeneous the  begin  experimental  available and  VI),  the  major  of  the  surfaces same  K,  Mg  factor  not  to  organic  of  the  of  This  significant There was  mentioned  of  squares,  was  a  mere  are  on  order as  that  size  of  data  on  pH,  the  (Tables  V  reason  as  latter  insignificance  configurations they  are in  members results  case  positive  the  of  that  interaction response  of  the  of  the  would  be  effects  of  (W  x  S).  to  irrigation  the  this  effect  compared and effect  30.8% of  to  in  P  at  when  x  factors  three  factors on  water  level.  this  i s not  contribution  the  factorial  on  and  But,  as  by  sum  arrangement  phophorus  contributions, irrigation  (W)  conclusive  the  and  each  statistically  1%  schedule  there  two  dependent is a  significant  VIII)  any  there  that  to  simple  a l l the  is  (Table  When  interpretation  yield  paragraph,  due  40.8%  where  preceding  seen  respectively  nature,  between  case,  indicates  was  a  this  conclusive especially  i n f l u e n c e on  order  1.2%.  the  in  content  differences  of  this  second  SS,  and  matter  interaction  in  latter  be  smallness  m)  the  essentially  Yields  never  statistically  i t can  were  statistical  Thus,  experiment  their  in  the  accept  the  and  units  treatments.  first  that  the  14.6  to  indicating  Irrigation  or,  for  surfaces  treatments a  by  inclined  responsible  factorial  considered  since  soil  differ,  either  this  be  m  do  individual  other.  and  (b)  (39  treatments.  a  indicate  Ca  and  Considering  block  Effect In  with.  would  population  4.3.1  blocks,  area  &  one  attributed  is  to  into  the yield  with  physical becomes  67  clear: might  that or  might  separately limiting evident but  i t was  in  the that  amount of  been  an  separately  and  In  W3.  It  to  the  the  dry  matter  yield  different  should  be  (0.05  the  here  connected  (not  in  experimental  design  they  have  each  and  SxW by  other  interaction sum  %•)  of  and  was  squares,  these  effects.  two  this  The  high  will  argued  be  scheduling  was  yield  of  at  i t  did  1%  did  not  in  tended  cowpea  than  W2  either  and  W  to  did  detected as i f  effect  Wl  a  that  p l a n t s were  not  those  The  of  or  were  so  in  this  alongside VIII,  third  in  their  result;  the  of  S i t  irrigation  impact amount  the  evident  square(SS),  S,  the  (17.6  influence  this  irrigation  W1  contribution  ranked  greater  tested  W3  in Table  of  well  and  independently sum  by  site.  discussed  shown  i t is yield,  i t is statistically  text  the  S  substantially  by  exert  alone,  sense)  responsible for the  words,  treatments  level.  act  contribution probably  of  be  As  Furthermore,  later  procedure  to  interactive  that  variables  (40.8)  W.  of  S  other  between  statistical  isolation.  significant  in yields.  treatment  matter  in  demonstrated  differences that  not  from  tested  could  this  hence  were  cowpea  and W  and  production  at  yields  that  In  P  that  out  level)  i t  study  differences  intimately  that  with  i n cowpea  ruled  while  mentioned  this  possibility  be  if  affected  effects  cannot  evident  of  water  factor  factors  set-up.  result  irrigation  other  factor  experimental  unimportant alone  by  i  important  design,  were  significantly  of  influenced  i t s interactive  general,  treatments  an  another  experimental  have  be  discussion  because  the  not  highly  on of  dry  water,  68  Since  no  that  fell  on  the  cowpea  nonstress ANOVA  attempt the  (Figure  VIII)  From 5),  evident  and  S4  produced the  August  deg.  C  early  to  those  apparent after  followed i n view  ultimately. 7  perhaps,  fruit  preclude  (night the  have  S2,  S3  to  concept the  high  yields with  suggested early  (4.9  0.01  and  (the  The  level  for  wilting  the  mm  stress  schedule.  S  point  gravimetric  cropping  S4  period,  i t  Stage-of-Growth) times  especially  rainfall  total)  and  from  of  to  of  plant  was  lower  conditioning"  to  lower S3  a  8  obtained  from slower  the  of  allow  below  It appears  reduction  period  still  contemplation),  relatively  S2,  plots  significantly  yields  however,  possible  this  rate  S5.  matter  vegetative  of  in S1  temperatures  was  and  some  August,  differed  dry  that  in  soil  "crop  yields  prevailed  i f i t were  of  were  that  and  Growth  compared  comparison  i n the  not  nodes  of  the  success  and  the  water  at  with  deficits  trifoliates  These  (1973),  stresses  and  schedules.  when  season,  several  10th  water  other  S4  irrigation  permanent  and  germination  yields  rainfall  rainfall).  the  and  Hsiao  (46.8.mm  f l o w e r and  of  the  stress  July  of  irrigation  significance  (the c o n t r o l )  amount  different  throughout  might  number  levels by  E)  yield  and,  stress  the  grain  of  to  the  the  comparison  and  i n September  ultimate  group  the  during  of  moisture  26th  high  crop  S1  under  Despite S1  by  (Appendix  June  on  knowledge  that  were  throughout  a  control  subjected  indicated  and  determinations  between  was  to  plots  p e r i o d s depending  (Table  plots  made  different  crop  treatment.  was  was  in  S1  former  from  water' them  for a l l fertilizer and  S5  in leaf crop  plants. area  will  from often  69  minimally reduced  affect  leaf  yield  area  can allow  maintain  assimilative  accumulated  during  night  because  temperature irrigated excelled of  in yield  associated optimal and  leaf  area  seasonal  development  normal  yieldT  improving  frequently  but with  irrigation  and twice  is  to the frequency  concerned from  on  this  50% a l l o w a b l e  water  deficit  but  further  on  within S2  depletion  and  in  waterlogging  S5  were  healthy  produce  reasonable  by r e d u c i n g t h e  of i r r i g a t i n g  yield  to  each  ( S 5 ) . But  there  25%  the  > W3,  soil  crop i s frequency  maximum W3  frequency  yield  more  at  i n the order  irrigation  > W2  use  as f a r as t h i s  i n S2  of other  of a  maintaining  Increasing  ( S 3 ) ,the i d e n t i c a l  and the c h a i n  requires  while  interval  site.  t o W1  usually  vegetative,  consumptive  of i r r i g a t i o n  increased  reversed  are  which  be a c h i e v e d  the design  of t h i s  the conclusion  the  that  would  design  depletion  plants  stages.  could  ecological water  S5)  yields  by t h e t e c h n i q u e  the  within  increase  the i n t e r v a l S5  half  with  as  optimally-  and  during  (S2)  yield  water  limit  plant  interval  on t h i s  (such  That  photosynthesis  VII i l l u s t r a t e s  allowable  a  maximum  and n a t u r a l maturation  irrigation  f o r growth a t  factors  (S3  to  assimilates  and the maintenance  active  Table  penetration  requirements  deficiencies).  that  because ( i )  ( i i ) ,  growth-1imiting  (1981),  maximum  Furthermore, the  and  exceed  organ  light  u l t i m a t e l y i s i n agreement  photosythetically  reproductive  canopy  frequently-irrigated  et. a_l with  greater  nutrient  and  reproductive  capacity,  other  and  Stegman  a  t h e d a y may  of  (S2)  of  trends  > W2  to 3  soil > W1 times  recorded  probably  complications  in  because of set forth  70  once  the s o i l  lower down  in this  and, also  foliage good  looking  quite  use  of  zone  (IRR + R water  + D)  using  water  with  of sugar moisture  moisture  accumulation setback be  will  i n growth  further  but  to yield  borrowed  result  from  and,  is difficult. under  possible optimally  Clements  since  water  use.  (1) t h e  consider  important  water  variable  applied  Indeed,  cannot  Clements  for irrigation  during  demonstrated  that  significantly  applied  too  triggered and  root  as  late, a  a  and  drought  carbohydrate  complete  recovery  from  this  The e f f e c t  of water  stress  will  interaction  reasons  and s t a t e d  as  succculent-  through  to  growth  i t s  have  acceptability  the  already  slower  of  passed  a s an  being  quality  grounds,  dropped  has  the  (S4) which  physiological  development,  water  plant,  plot  t h e most  fail  water  level  stress  discussed  treatments, plants  the  cane  i n the control  i t s  irrigation  plant  yield came  usefulness  might  the  procedure  on  m o i s t u r e as a g u i d e  after  in  that  season  (2) t o t a l  of i r r i g a t i o n  reaction  case  the i r r i g a t i o n and  on  but l i m i t e d  in this  consequence the  that  quantity  can have  tissue  phase  by  demonstrated  correlated  tissue  i s a debit  plants.  right  once  which  was  but i t almost  Also,  t h e S2  in  vegetative  irrigated.  followed  over  (1964),  recorded  produced  quantity  directly  2 a n d 5,  plants  distribution  be  not only  The c o n t r o l  total  i t s own  of magnitude  poor,  results  the  to plots  inadequately  foliage  These  In f a c t ,  stage-of-growth scheduling  clearly was  relative  order  the  forage.  total  so t r e a t e d .  plot  t o t h e same  (S1) was  was  with  f o r the failure  been  offerred  above.  by  fertilizer o f S1  a n d S4  the  points  71  However, is  that  was  not  significant  irrigation as  distribution under  a  which  amount  important of  of water  was  to reiterate or  total  i n i n f l u e n c i n g cowpea  the applied  the crop  point  water  grown.  or  the  at this  juncture  evapotranspiration yield  scheduling  as  the  time  procedure  72  Table  IX  FERTILIZER  - S x P Interaction  S  C  H  on  Cowpea  E  D  Yield,  U  L  t/ha  E  S  S1  S2  S3  S4  S5  PI  11.7  11.8  10.9  10.7  14.7  P2  12.1  13.2  13.8  11.5  19.0  P3  14.0  15.2  17.3  14.3  22. 1  P4  15.1  16.2  17.8  15.0  24.0  P5  15.9  16.8  18.0  14.8  21 .9  - P x W  Interaction  LEVELS  Table  X  FERTILIZER  on  W A T E R  Cowpea  L  E  V  Yield,  E L S  LEVELS  W1  W2  W3  PI  11.7  11.9  12.3  P2  13.3  14.4  14.0  P3  15.9  16.6  17.3  P4  17.2  17.4  18.2  P5  16.6  18.1  17.7  t/ha  3o-|  24  Figure 7 - Interaction of S and P Treatments on Yield  H  o Q  LJ  I CO  >-  Legend  LxJ  A SCHEDULE 1 a  X  SCHEDULE 2  •  SCHEDULE 3  EI SCHEDULE 4 S  P2  P3  P4  APPLIED FERTILIZER P (kg/ha)  P5  SCHEDULE 5  74  Examination o f S x P Interaction on Y i e l d :  X  S1P2  S1P3  S1P4  S1P5  x X X  XX  X  S2P1 S2P2  .  S2P4 S2P5 S3P1  S3P5 S4P1  ! 1  X X X X  X X X X X X X X X X x x x X X x x X X X K X X x  i  S5P1  x  x  S5P3  X  S5P4 S5P5  X = 5% s i g n i f i c a n c e e.g.:  X x X X x  X X X x r  S5P2  *  S5P5  X X X X X X X X x x X X X X X X x x X X X X X XX XX X X x X* X X X X X x x x x X X X X X X X X X X X X XXX X X X X X X X X X X X X X X X X xx x x X X X (x)x x x x x x x x x x x x x x  S4P5  S5P4  S5P3  S5P2  S5P1  S4P5  S4P1  comparison)  *-  X  X X X X X  S3P5  X  S3P1  S1P5.  X  S2P5  S1P4  *  S2P1  S1P3  SlPl  S1P2  SlPl  (Mann-Whiteney non-parametric  S4P3  Figure 8 -  level  An X corresponding to say, the i n t e r s e c t i o n point between treatment combinations S3P1 (ROW) and S4P3 (COLUMN) means that there i s a s i g n i f i c a n t difference at 5% l e v e l between these two y i e l d s ; ( X ) .  20-i  Figure 9 - Interaction of W and P Treatments on Yield  cr  .-C  c o  >-  14H  OH  LxJ  f—  Legend  !<  Cr: Q 10 H  8  PI  P2  P3  P4  APPLIED PHOSPHATE (kg/ha)  A  WATER LEVEL 1  X  WATER LEVEL 2  •  WATER LEVEL 3  P5  76  4.3.2  Effect  of  Forage  Phosphorus  yield  fertilizer  Fertilizer  increased  applied  and  with  these  increases  significant  agreement  that  of  Malik  (1974)  yield  up  to  optimum  cowpea  forage  In  this  experiment,  irrigation  schedules  S2,  level  and  in  the W2  W3  control, at  P5  S1,  reasonable  response  and  of  Tewari  of  worthy  P  of  2  mention  here  is  5  P  in  still  P  the  not  Malik  more  nodules  greater  importance  is  exerted  tremendous  influence  in  study  the  in  forage  it  in is  fertilizer  with  India,  of  on  increase  substantial  part  phosphorus  at  agreement  a l l seeds  In  maximum  shortly,  (1980)  than  at  especially  The  this  5  in  phosphorus  planting,  2  5  Rhoades  to  P 0 .  fertilizer.  and  (1974)  in  water  2  improve  in  in  P 0  and  although prior  is  is  under  was  follow  be  obtained  further  later  will  application  produced  the  of  unjustifiable.  was  that  with  given  that  Nigeria  Rhizobium  thriving  be  Nigeria,  nodulation  non-specific  would to  dose  to  increases  kg/ha  kg/ha  fertilizer  increasing  to  in  same  88 was  70  perhaps,  crop  P 0  (1965)  (1983) on  and,  with  to  of  phosphate  result  obtained  dose  of  found  This  yield  the  response  that  kg/ha  who  level  were  level.  S5  with  reasons  cowpea  Nangju  Effect  with  of  and  interactions  say  80  S3  level  for  1%  maximum  S4  the  on  to  beyond  works  yield  But  discussion  level  W1  dose,  production. the  at  fertilizer  phosphate  at  an  Yield  increasing  statistically with  on  were  in  the Kang  U.S.A.  but  it  is  innoculated  fertilized  plants  unfertilized  ones.  Of  kinetics  could  have  response  to  yield  that  fertilization. A  careful  study  of  Table  VII  further  reveals  that  while  77  consistent  yield  recorded  under  results  in  could  P  which be  irregular  could  be  4.3.3  Effects  be  effect,  of  a  these  due  in general, of  to  crop the  this  when  to  in  water  supply of  to  lower  applied water  section. study  It have  is deficient  applied  predict.  of  irregular  the  findings  were  corresponding  next  simple  Often,  effects  any  simple  of  the  interaction  of  Referring a l l same  of  effect  presented  or  fertilizer the  response  any  term.  the  same  irrigation order  of  single  factor  means  and  differ  level  of  and  IX  or  Fig.  schedules  0  kg/ha  P 0  applied  up  to  including  5  the  one  S  x  of P  Figure  (P).  In  another  in  i t follows  and  the  the  other  magnitude factor  yields  (over  7  a  is  that  a l l  W)  graphical  data.  Beyond  and  upon  IX,  magnitude 2  on  production,  The  Table  Table  dependent  between  fertilizer  matter  depends  Yield  interaction  phosphorus  were  in  to  and  dry  Cowpea  significant  (S)  cowpea  illustration  I n t e r a c t i o n s on  factors  of  the  be  utilization  highly  schedule  influencing  for  and  S5,  d i s c u s s i o n i n the  difficult  Factor  was  irrigation  are  and  response  may  that  crop  S3  fertilizer  low.  There  the  S4 of  S2,  irregular poor  that  fact  both,  would  were  subject  the  phosphorus  schedules  and  however,  or  nutrient  S1  is a  out  S4  with  relatively  in  noted  pointed  and  This  fertilizer supply  irrigation  S1  magnitudes.  increases  7,  i t will  except  S5,  (approximately  a l l schedules P3  and  observed  yield  obtained  11.5  t/ha)  showed  then  be  sharp  diminishing  that was  at  response returns  of P1.  to  P  set  78  in  and  might  so,  depending  be c o n s i d e r e d  However,  with  although  yield  increased obtained  It  is  is  higher  indication  that  maintaining  how  l o t  would  frequently  -  with  S4. P4 a n d  level  higher  was  than  irrespective  of  those  of  the  this  of  S2,  soil  yield  can  be  1982) i t  produced This i s i s  essentially  improve  yield  waterlogging  there  irrigated  after  S2, f u r t h e r  is  occurred  that  of  irrigation  could  apparent which  S5  than  which  more  in soil  and  use,  at  recovery  irrigation.  moisture,  However,  left  S3  irrigation  given  and Tucker,  or stage  demonstrating crop  of crop  are  Forage  increasing  t o respond  15% l e v e l  higher  further.  still  fertilizer  reactions  thereby  continue  levels,  available  soil  was  residues  gave  levels.  result  1967; a n d H a g i n  improve S5  this  irrigation,  irrigation  frequency  injurious yields,  no  and  a l l fertilizer  still  u s e , P3  S1  the f e r t i l i z e r  was  explore  zero  to  a high  for  obtained  schedules  the present  a  that  indicating  reduced  to  (Larsen,  than  S3  other  yield  For a l l f e r t i l i z e r yields  level  was  when  of f e r t i l i z e r  level.  under  that  essential.  at  this  important  phosphorus  harvest.  an  kg,  But g i v e n  obvious  yield  slightly  7 ) , and perhaps  phosphate.  fertilizer  any of the other  i n S1  (Figure  applied  10  treatment  production P5  maximum  decreased  under  the economics  an optimum  S5,  by  fertilizer  on  i n S3  are  and  ledto  limits  without  to  negative  effects. Phosphorus possible its  has  limiting  immobility  long  nutrient  in soil  been  claimed  f o r deep  root  and i t slow l e v e l  (Black,  1966)  development  as  a  because  of  of a v a i l a b i l i t y  i n many  79  subsoils.  P  moisture  level,  percentage  (Pierre  follow  this  uptake  by  Plants  irrigated  several  which  plow  layer  presence growth  when was  of  (because  of  subject  deeper  elongation  the  upper  to  a  the  was  in  roots  result  of  response  strengths  is  was  s u f f i c i e n t to plots  than  fertilizer  not  at  nutrient  explained  by  to  P  the  the  S4,  the  improved  root  locked  (1972)  as  exhibited been.  But  surface  overall  optimum  effort  generated This  another  in  deeper  i n the  the  levels.  not  pronounced  explore  have  yield  was  deficiency  and  why  There  this  otherwise was  uptake  although  was  fertilizer Veits  Since  levels  therefore,  accomplish  that  at  nutrient  soil. S1  the  stress  depressed  in  extend  i t would  surprising  similar  of  moisture  to  and  and  have  surface  to  to  S1  believe  attributed  above  (S1)  in  might  the  to  plot  plots.  penetration  reason  which  described  the  periods  forcing  applied  phenomenon  deficit)  more  i t  other  subsoil  soil  wilting  phosphorus  drying  during  root  of  by  permanent  subjected  their  rest  periodic  is  layer, not  the  i n the  plant  were  layer  greater  since  to  the  non-irrigated  (S4)  to  affected  results  affected  horizons  There  root  as  doubt  moisture  substantial.  layers  plot  P  The  i n the  compared  lower  of  evidence  no  available  in the  strongly near  ejt a l , 1 9 6 5 ) .  inadequately  utilization  is  particularly  fact.  times  crop  is  in the  form  of  'drought'. Within significant The  any  plot  difference  Mann-Whitney  treatment  means  was  as  well  in y i e l d  U-Test  for  adopted  in  as  between  between  S1P1  plots, and  non-parametric studying  S  x  P  S1P5  there or  was  a  S5P5.  comparisons interaction  of and  80  the  results W  x  meaning not  are  P  the  acted  performance; levels  P  same  of  on in  irrigation  to  acceptable.  been  in  criss-crossing insignificant further under is  at  what  is  scrutiny  and  W3 that  of  than water  W1  the as  0.05  at  or  P  same  for  measured  by  equal  to  the  effect  in  this  if  the  yield  are  as  factor. on  crop  yield  fertilizer  was  level  9).  to  There  P4,  But  these it  what  was  is  levels  in  any  left  Fig.  one not  to  the  yield  is  9,  increase,  an with  were  economic  curves  clear  when  of  under  accumulation)  practice,  are  Table  main  (Figure  apply  W3 (at  of  given  up  to  as  interaction,  applied  orientation  differences  that  P  these cowpea  the  accurately  matter  In  level  W2  a  was  that  were  were  considered.  closeness  of  x  similar  influencing  effects S  a  interaction  them  (dry  significant.  of  to  has  variation,  as  water  P  in  effect,  any  yield  level  direction  in  in  W  effects  devoted  Unlike  x  and  speaking,  of  chance  interactive  X.  The  any  estimated  irrigation  choose  of  and  magnitude  water  explanation  was  P  P  other  simple  fertilizer  statistically  higher  effects  had  That  each  within  main  of  in  of  and  of  significant  statistically  error;  x  not  effects  other  increase  increase  A  the  Table  order  obvious  similar  simple  W  amounts  farmer  means,  experiment  presented  was  8.  interaction.  experiment  Data  all  x  the  corresponding  entire  Figure  independent  experimental  the  S  significant  factorial  in  interaction  to  factors  all  shown  their  and  manifestations  of  the the  level). X  reveals  any  given  that P  yields  level.  a v a i l a b i l i t y maintained  high  A  were  possible intensity  81  of  P  in  soil  (diffusion to  the  albeit at in  solution  factor)  other not  say,  a  as  more  dictates  the  solid  as  modified  root  and  sporadically  available  with  irrigation In for  amount  field  and  Pioneers  Bauder  limitations  recommendations. individual adjacent  small  the  have  a  from  when  applied  at  is  due  quite  to  store  water grown more area,  house  factors  higher rain  in  such  nutrient  water  towards  any  soil  optimum;  Additional under  in  defined  the  contributed  was  were as  and  sizes  at  was  increased  given  a  crucial  Variable  cautious basis  because  of  level  of  recommendations the  Design' of  the  the  2)  given  which  agronomic  fact  be by  are  1973  statistical  that  surrounded  therefore  of  Torrie,  (Fox,  reliable  always  as  validity  ( S t e e l and  firstly,  design  (Figure  for  are  cannot the  deriving  requirement,  always  treatments  secondly,  individual plot  water  'Continuous  design  This  aimed  is  1975)  treatments and  must  fertilizer  irrigation  randomized,  solution.  utilization  design  this  rate  P  yield,  plants  required for  in  in  stress  uptake relative  W1,  favors  the  W3  increase  level,  that  P  water.  e_t a l , of  than  under  increase  treatment  development  irrigation  of  with  fertility,  experiments  experimental  1983). and  of  crop  fertilizer  the  hence  increased  yield  recommendation  soil  consistent  observed  shows  quantity  the  availability  yields  the  replenishment  extensive  a  higher  water  soil  stated  into  in  only  by  nutrient  phase  more  result  the  ensured  statistically,  fertilizer  than  as  Also,  irrigation  This  quantity  the  levels.  single  deficiency  well  culminating  significant  order.  under  two  as  Fox  by  the the  considered (1973)  feared  to  has lead  82  to  more  (Hanks  variability.  e_t a l , 1976)  design  can  be  randomizations may  not  concluded  a of  very the  always  substantial  irrigation  be  a  design  handy  for would  be  environment  which  the  4.4  Effect  of  total the of  N  and  printout elemental  were  done  programme Science by  an  from  on  analyser  an  Apple in  the  The  (Table  XI)  to  with  Table  XII  i s the  e v a l u a t i o n of  a  similar  nonsignificance P  was  uptake.  of  ease  to  of  P-uptake.  of  is  the  a  no such  crop  the  and  of  D.  the  of  solution  appropriate  Columbia  The  of  computations  computations  the  as  Soil  produced  results  experimental  were  design  interpretation.  variance  table  Phosphorus  obtained  for  the  Table  portion  into  British  matter  of  of  using  dry  data  are  that  necessary  the  The  system  study  extracted  with  analysis  and  this  C  in Appendix  for  small  for determinations  computer  conform  VII,  the  as  University  presented  trend  leaf  II  the  Utilization  Appendix  while  of  conducted.  prepared  results  statistical  on  in  are  Table  effect  was  lack  replications  except  was  the  considering  for  of  and  and  limitations  Fertilizer  foliage  the  available  line  the  experiment  concentrations  computer  results  autoanalyser.  Laboratory.  the  in  on  with  rearranged and  P  cowpea  The  levels  offers  used,  tool  limitation  design  within  Irrigation  Digested  water  investigators  properly  recommendations  recommendations for  when  research  serious  studies.  subsequent  that  effective  o p p o r t u n i t i e s the  experimental doubt,  Fortunately,  S XIa  obtained  uptake  yield x W  x  offers  followed  except P  upon  that  interactive an  indication  83  of  improved  heavier study  P  rates  of  stands  that  apparently  were  on  respectively,  are  irrigation  depend  on  could  be  as  would  treatment and  under  that  amounts  and  These  4.  were  and  results  of  a  crop  "minimum" these  nutrient  However,  to  Figures  XIII  and  that  10 XIV  under  i s forced  phosphate  yield  by  as  because  the crop  in soil  that  the  appropriate  bacterial  Ca  so c l o s e  Again,  and  itself  —  to  uptake  a  pattern  (3 -  5%  N  were  the in solid,  differences levels  variations could  be:  capable  various Tables  are  obvious  receiving  exist  in plots  (a) a p r o o f  of  P  the  that  uptake  fixing  1  and N  N  (b)  given  innoculation.  the plant  a n d Mg  from  so d i d n o t a f f e c t  a l lplants  digestion,  samples  of N uptake  to the fact  K,  and  impression  at a l l f e r t i l i z e r  of water.  due  elemental  in  insignificant  not d e f i c i e n t  for  as  produced  performance  summer,  this were  occur  Tables  i n which  during  not  argument  the  i n the f i e l d  was  Upon  with  one  levels  the  schedules  different  crops  (S1)  of  of  nutrient  sufficient  plots  with  tolerate.  combinations  a l l  favorable  absorb  one  rains  uptake  XIII)  larger  this  as  the r e s u l t s  precipitation.  or a minimal  variable  Nitrogen  XII  leave  unpredictable  farmers  to  graphical  clearly  the  to  well  fertilizer  irrigation  weight able  of  The  zero  the occasional  which  of  as  deficiencies did  stress.  received  irrigation  In g e n e r a l ,  rates  nutrient  adds  11  zero  that  (S4)  capitalize  with  the needs  moisture  irrigation plants  heavier  satisfy  and  result  uptake  fertilizer.  that  to  irrigation  few  of  suggest  required  and  nutrient  were  extract  was  done  directly  by  d i l u t e d and reading  analyses on  an  84  Atomic  Absorption  presentation  Spectrophotometer  of  the  result.  were  within  elements  in  leaf  necessary  to  subject  there  i s no  correlated The higher  dry  literature to  (0.01  and  observation  1966; and  to  of  P  applications  that  is a  by  plants  apart  uptake  of  application  successively  being  significantly  Nangju  relative  was  Sumner  and  that  nitrogen  unusual Boswell,  complementary.  confirm  is  receiving  works  and  to  cowpea  with  Kang  are  by  not  Besides,  is consistent  and  nitrogen  P  a  these  i t was  that  (1983)  and  that  of  are  of  finding  Hall  1972;  Xlb  analysis.  from  agrees  the  range  uptake  and  that  in Table  elements.  uptake  level),  close  statistical  suggest  these  a  data  concentrations  results  Veits,  information  such  data  to  The  yield  phosphorus  cowpea.  of  increased  matter  Ziska  to  any  phosphate  different  the  and  this  as  1981)  Malik  was  the  (1974),  (1983).  it is  However, N-P  of  with  The  not  related  known  (Black,  that there  phosphorus is  r e l a t i o n s h i p i s true  no for  Table Total  N & P read  on A u t o  TOTAL  P  FERT.  -  Plant  Analyser  P (ppm  in  L  I  LEVELS  XIa  from  Results.  original  0  W1  without  dilution.  T  III  W2  digest  solution)  II W3  Analyses  W3  S  IV  W2  W1  V W3  W2  W1  p1  6 4 .. 29  56 . 20  58 .. 24  65 .04  51 . 97  77 .. 7 1  58 .. 1 1  50 .43  6 0 .. 3 3  5 0 .. 4 1  5 0 . . 54  P2  4 2 .. 5 0  7 8 . 75  47 .. 32  68 . 6 5  61 . 5 2  6 8 .. 4 8  52 .. 16  45 . 0 6  70 .71  6 4 .. 24  57 .. 8 6  P3  6 9 . 59  73 . 8 0  7 2 ., 5 0  72 . 2 4  5 3 .. 5 6  6 5 .. 3 6  82 .. 56  6 4 .. 0 2  86 .. 8 3  74 .. 9 3  6 7 ,, 59  P4  8 0 .. 0 5  9 7 .. 6 0  7 8 .. 4 6  73 . 0 4  67 .45  55 ,. 3 7  74 ,. 4 2  5 0 . 13  88 .. 2 3  8 4 .. 5 6  7 2 .. 8 9  P5  40 . 52  7 2 . 36  6 9 .. 75  79 . 18  59 .66  59 ., 6 9  75 ,, 27  44 . 24  66 . 0 2  79 .. 18  74 .. 4 6  TOTAL N (%  I  in  plant  II  solid)  III  IV  V  P1  4.32  4.89  4.22  4.02  3.84  2.70  5.30  4.44  4.27  4.10  4.09  P2  1.11  3.99  5.07  4.76  4.50  4.42  4.45  3.86  3.78  4.20  4.28  P3  4.50  4.42  4.84  4.56  4.24  5.23  4.24  4.68  3.58  3.94  4.22  P4  3.68  3.81  4.74  4.22  4.79  4.76  3.87  2.50  5.04  3.75  4.33  P5  3.59  4.48  3.43  4.14.  4.94  4.90  4.21  3.65  5.10  3.98  4.38  CO  FERT. LEVEL  P1  P2  P3  P4  P5  I ELEMENT  Table  Xlb  Total  K,  -  Plant  Mg a n d  Ca  II  Analyses in  Results  % plant  of  III  contd. foliage.  IV  W3  W2  W1  W3  W2  W1  V W3  W2  W1  K  2.85  1.92  2.47  2.63  2.19  2.99  2.37  1.62  3.37  3.02  3.20  Mg  0.58  0.99  0.62  0.62  0.62  0.65  0.32  0.38  0.98  0.53  0.75  Ca  0.90  1.45  1.15  1.00  0.83  0.95  0.65  0.68  1.00  0.85  0.80  K  0.53  3.97  1.74  2.53  2.93  3.02  2.00  1.74  0.59  3.55  2.72  Mg  0.08  0.98  0.53  0.73  0.65  1.22  0.38  0.28  1.07  0.88  0.77  Ca  0.33  1.02  1.03  0.90  1.03  0.88  1.28  0.65  1.08  1.05  0.75  K  3.32  3.44  3.25  3.55  3.39  2.32  3.55  2.35  3.55  2.93  1.82  Mg  1.05  0.68  1.12  0.88  0.65  0.40  0.88  0.47  1.03  0.85  0.62  Ca  1.23  0.80  1.38  2.23  1.10  1.00  2.23  0.90  1.10  1.18  1.08  K  3.77  2.99  3.82  4.85  2.94  2.13  3.37  1.87  3.02  3.07  3.17  Mg  1.15  0.47  0.83  0.95  0.65  0.85  0.85  0.40  0.80  0.75  0.80  Ca  0.90  1.52  0.85  1.03  0.88  0.68  1.33  0.83  1.00  0.65  0.95  K  2.90  2.72  2.80  3.97  2.13  2.37  1.62  1.60  2.30  3.49  2.54  Mg  0.85  0.58  0.68  0.88  0.53  0.38  0.45  0.53  0.43  0.68  0.85  Ca  1.80  0.50  1.10  1.08  0.58  0.85  1.00  0.95  1.10  0.83  0.93  87  Table  SOURCE  XII - Analysis  d.f  SUM OF  Treatment  of Variance  SQUARES  f o r P-Uptake  MEAN  SQUARES  F  - TEST  (36431.65)  S  2  458.77  229.39  10. 92  **  w  4  9369.81  2342.45  1 1 1 . 55  **  p  4  9853.81  2463.45  1 1 7 . 31  **  S x P  8  630.05  7 8 . 76  3. 7 5  **  S x W  8  1746.35  218.36  10. 40  x W  16  13696.04  856.00  4 0 . 76  **  S x W x P  32  676.32  21.14  1 .01  ns  Block  1  0.01  0.01  Error  74  1546.98  20.91  Total  1 49  37978.63  P  All  values  0. 00 n s  a r e uncoded  **  = significant  a t 0.01  ns  = not s i g n i f i c a n t  F  = Treatment  level  a t 0.05  level  Mean s q u a r e / E r r o r  Mean  square.  88  Table  XIII  -  S x  FERTILIZER  P  I  LEVELS  Interaction  R S  R C  I H  G E  S2  S1  on P- U p t a k e ,  T  A D  U  ppm  I  0  L  S3  E  N S S5  S4  P1  6 4 . 29  59.83  62.60  50.43  53.76  P2  4 2 . 50  64.91  60.72  45.06  64.27  P3  6 9 . 59  72.85  67. 1 6  64.02  76.45  P4  8 0 . 05  83.03  65.75  50. 1 3  81 . 8 9  P5  4 0 . 52  73.76  64.87  44.24  73 . 22  Table  XIV  FERTILIZER LEVELS  -  P X W Interaction  IRRIGATION W1  on  P-uptake,  WATER W2  LEVELS W3  P1  57.68  60 . 22  56.64  P2  56.75  57.02  63.21  P3  71 . 2 0  69.28  69.56  P4  70.11  69.71  76.69  P5  62.71  58 . 68  56.56  ppm  90-i  Figure 10 - Interaction of S and P Treatments on P-Uptake  oo  Legend A SCHEDULE 1 X SCHEDULE 2  PI  P2  P3  P4  FERTILIZER LEVEL, K g / h a  •  SCHEDULED  H  SCHEDULE 4  £  SCHEDULE 5  VO  P-UPTAKE PER PLANT, p p m  ID  •  X  > AT  AT  ST r —  CO  CO n m m CD X) TV •r- r~ r~ i< in m < m < n m m [— M  o I  cr  — *  CD  06  91  4.5  Water  Use  Crop amount by  water  of  the  dry  crop  as  matter is  use  of  the  =  produced  the  of  produced.  WUE  (WUE) per  soil.  water  In  may  unit  This  transpiration  mass  expressed  efficiency  matter  from  reciprocal 1913)  Efficiency  term  referred  work,  of  is  to  use  as  water  the  taken  essentially  (Briggs  per  water  defined  volume  transpired  this  be  unit  and  the  Shantz,  mass  efficency  up  of  dry  (ton/ha/mm)  as:  Y/ET  [4.1]  where: WUE Y  i s as =  ET  dry =  Seasonal in  the  matter  above,  yield  seasonal water  ET  was  latter  before  defined  irrigating.  performed  at  estimation  of  schedules.  In  the WUE  mm.  from  could  equation be  practice  end under  Results  ton/ha,  use,  estimated  equation  ,  of  of.  [3.3].  computed however,  the  In  from  these  irrigation  the  different  such  computations  principle, historic  computations  period  to  irrigation are  AS  data were  facilitate  regimes  presented  in  and Table  XV. It (a)  can  increasing  maintaining water but  be  use an  seen yield  equal  efficiency "optimum"  in equation and  that  maintaining  yield per WUE  4.1  and se  —  WUE  equal  may  water  d e c r e a s i n g water  i s not  maximum  the yield  be  objective  increased use  use. in  relationship,  or  by (b)  Maximizing this  study  subject  to  92  local  c o n s t r a i n t s of water  water  planners  crop  (S1)  Table  gave  lower  than  latter  irrigation applied  those were  water  use  tool f o r  requirements  treatments  of  the  the control  plot  reductions.  Maintaining  of  as expected lowered  individual  irrigation  irrigations irrigation  permitted  applying  o f S3W1  grains,  irrigation  filling.  a n d S5W1  this  cutoff  September  fewer  water  began,  watered  i n Table  when would  XV;  would  during  (as  periods involved  indicated  t o moderate  associated and  with  i f this have  S5W1  been  crop  rainfall  a l ,  some  t o S5W3. rainfall  to favor  sufficient  high  e_t  were  that  by  yield  for  with  seasonal  tended  was  occurred  a s was d e m o n s t r a t e d  significant have  water  treatments  S2W3,  irrigations  individual  1971; a n d S t e w a r t  efficiency S2W2,  Highest  with  generally  slight  i n combination  practice date  stress  and Dusek,  like  WUE  moisture  much though  WUE's.  used  and  adequately  levels  o r no r a i n f a l l  were  and  was  irrigation  occurred  soil)  (Musick  Maximizing  results  some  low  when  little  intervals  incurred  water  associated  either  when  rainfall  sampling  1980),  relatively  occurred  dry periods  appreciable  yields,  while  use e f f i c e n c y , i.ts y i e l d  at  irrigation  that  that  efficiencies  gravimetric  as  water  o f S 2 , S3 a n d S5 a t W1-W3  water  longer  treatments  for  future  i t i s apparent  obtained  during  when  when  XV,  the highest  irrigation  or  in assessing  i s a desirable  in question. From  the  availability,  by t h e grown early  occurred for  grain  Table  XV -  Yield,  IRRIGATION SCHEDULE  IRRIGATION  INTERVALS  DEPTH (mm)  (days) J  -  J  -  Evapotranspiration  SEASONAL No.  of  and Water  RAINFALL  IRRIG.  (P),  SEASONAL ET,  mm  138 . 8  W1  31.2  W2  106.8  W3  169.8  W1  10.4  W2  35.6  W3  56.6  S5  Note:  15.6  W2  53.4  W3  84.9  Water  Use  USE  (t/ha)  EFFICIENCY  13 . 76  99 . 1  326.0  1 1 . 26  34 . 5  W2  779.6  15.44  19.8  W3  1157.6  17.92  15.5  W1  242.8  18.80  77 . 4  W2  494.8  14 . 74  29 . 8  W3  704.8  13 . 0 8  18.6  13 . 24  27 . 7  46.8 478 . 4  4 - 4  Efficiency  (Y)  W1  30 SEP  W1  WATER  78 . 1  10  AUG 169.8  YIELD  13.1  1 0 - 8 - 8  JUL  S4  mm  Results.  A  UUN  S3  Efficiency  SEASONAL  S1  S2  Use  TOT.  is  defined  as  87.7  226.5  kg/ha/mm  as  W1  263.6  18 . 0 0  68 . 3  W2  566.0  21 . 2 2  37 . 5  W3  818.0  21 . 9 2  26 . 8  given  on page  90  CO CO  94  95  The  high  scheduled of  the  yield  irrigation  fact  that  to  seasonal  irrigation  using  obtain  seasonal  (1975),  and  here be  that  but  to  of  Low to  the  full  reasonably  sprinklers water  use  occurences irrigation  when  the  soil  previous  as  was  this  efficiency  of  heavy  in  each  could  S3,  particularly  4.6  Crop  Production  Functions  The  economic  evaluation  development of  the  are  potential the  water value  needed  to  p r o j e c t s to  optimum  uses.  of  marginal  often  i n W3  allocation  Estimates  of  by  to  is  On  extent, and  farmer  on  Raats to  add  may  not  irrigations over  the  and field  feasible. S2  were  due  occasions  the  from  that  somewhat  some  of  soil  and  important  distribution  two  water  reduced  size  in  the  Rawlins  It  the  on  wet be  be  from  indicative  rewet  conditions, a  values  case.  modera~tely  may  practice  rains  are  irrigation  (1978).  water  S5W1  relying  reduce  good  obtained  largely  suggested  irrigation  makes  irrigation  and  Krogman  substantially  obtain  use  surface  of  WUE)  and  to  requirements  rainfall and  S3W1  use  irrigations  Hobbs  under  able  s t i l l  water  high  necessary  efficient  smaller  expected  (and  combinations  i t i s not  profile  by  response  other  recent  responsible  principally  a  day  hand,  irrigating  rainfall  for  the  after  low  or  the  values  in  treatment.  of  resources product  of  assess supply of the  the  requires, water. the  use  inter  estimates  These  benefits  irrigation  existing  potential  water  marginal  water  alia, marginal  (or and  of  values  otherwise) in  s u p p l i e s and  product  and  water  from  determining competing imply  some  96  knowledge such  of the p r o d u c t i o n  knowledge (i)  i s o f two o b v i o u s  i t s importance  (ii)  the  of  simple  in crop  prediction  of  ultimate  conditions,  the  functions  interrelated climate are and  to  many  In  study,  related  to  water  single,  independent  adopted  yield  crop  different  1980).  results location, another.  at  and  a  major  developed related  allow  soil  water  to  reality  of these  which  soil  complex  and  fertility  and  production  often  functions  site-oriented  (Hanks  physically-oriented,  developed  fertilizer  to  predict  utilization,  and secondly,  yield  as  first  as dependent  to the experimental  widely  as  variables  data.  Model equations  were  evapotranspiration,  locations  differences  models  factors  regression  to  Hill,  use  and f i t t e d  Yield-Water When  site  simple  Many  as  and  f u n c t i o n s and as a  of which  and thus,  and  4.6.1  in  factors  policy,  in agriculture.  are  i n nature  applicable  climate  as  statistical  this  of  yield  important.  1980).  irrigation  been  are very  Hill,  were  have  other  of  production  instability  models  The e x i s t e n c e of  advantages:  handling  error  of production  Although  of water.  i n the study  systematic  component source  function  were  with Thus,  different t h e same  found  respect  the equations  equation  does  different  which  to soil  sites.  developed  could  Moreover, not hold  that  climate n o t be u s e d even true  crop  relations  indicate  and  relating  at from  for  there are  (Hanks to the  and  predict same  one y e a r  to  97  For  irrigation  transferred predict that  (that  future  are constant)  situations.  of Stewart  Y/Y„  management p u r p o s e s ,  (Stewart  1 - i% E T  =  =  D  of the  et a l ,  1977):  1  which  Y  = a c t u a l d r y matter m  = maximum  seasonal  site  One  in  Y  from  g  Significant  to site  most  can  a r e needed  simple  models  ET  (potential) yield  of r e l a t i v e  yield  qualities  of t h i s  water  can  estimate (b)  be m e a s u r e d  balance  equation  of ET, T a b l e  ET^  was  when m  =  Y/Y  ET = E T ; ET m  i s maximum 1 - ET/ET  considered  (c)  Model  is  d e s i r e d product  model  m  (Stewart  i s actual  seasonal  . much  for  t o growth  so  seasonal  n o t t o be  by  e_t a l ,  used  (In this as a  the equation  limited  and t i m i n g  study,  basis  for  by  where  growth  dry  matter  water  i f total  of i r r i g a t i o n  [Timing  stage,  influences ultimate  E T may  not hold  relation well  i s not of  refers  so  the simple  that  here  grain  that  ET.  , and  XV).  importance  cultivation related  or estimated  c a n be a p p l i e d d i r e c t l y  practical  is  vs ET .  m  [ 3 . 3 ] was  determined  was  to  yield  are: (a)  be  [4.2]  m  evapotranspiration and ET  = slope  that  (1 - E T / E T )  ETjj = e v a p o t r a n s p i r a t i o n d e f i c i t P  relations  irrigation  accounting  as a p r e d i c t i v e  to  timing  as  yield  so  only f o r tool].  1977)  98  Hanks ET/ET  m  ,  where  portion soil;  (1980)  In  occurred  from  to  three  that,  increase of a  given  (1980),  of  1 //3) .  a  ratio  to approximate the from  is transpiration Thus,  to the fact  while  the  (E) d i r e c t l y  0  (5 o f  fi  that 1.5  6  is  0  no  T,  the  (T) i s  always  ^  evaporation  would  mean  which  relationship  plot  dry matter  be p l o t t e d ,  would  reported  water  have  reduce  that  is a  true  between  the  from  of of  the yield  i s considered linear  analysis  the negative  S5 a r e p r e f e r r e d  3 points. 12 a s  ratio  power  for a  nutrient  achieves  site-specific,  of  yield  given  set  Stewart  under e_t  a  a l ,  greater  However,  since  no  accuracy  serious  do  reflect  level  of  this  than  that  to  ET/ET„,  the  and the  Rather  According  function.  in  and t h e rate  as n o n - l i m i t i n g  four  reducing  data  i s attainable  schedule).  only  validation  entailed  potential  use that  (such  model  Because  the predictive  in Fig.  yield  vs ET.  further  obtained  maximum  by t h e d i r e c t  because  shown  E and two-thirds  i n turn  inputs  Regression  and  was  irrigation  experiment lost  4.2  might  per unit  generalization  (1 -  mathematical  set could  the  a  was  o f any g r a p h  production  that  [4.2],  equation.  t h e model  primarily  ET the  equation  reliability  ET  surface  12 i l l u s t r a t e s  which  equation  c a n be  1 points  0  of  per data of  of  P =  the  in the  Figure  form  portion  the s o i l  of  by  zero,  by t h e f r a c t i o n  interpretation  points  that  i s due t o e v a p o r a t i o n  effect,  one-third  factors  is  m  that  the  approximated 1.0.  Y/Y  o f ET and  suggests  this was  regression. could  be p e r f o r m e d  response  for predictive  f o r S3 a s w e l l ,  t o ET under purposes.  this  schedule,  Under  S2,  but S2 the  99  measured 15.2  E T o f 326 a n d 7 7 9 mm  tons/ha  12.  respectively,  Measured  yields  respectively.  gave  using  yields  the regression  for this  Similar  predicted  plot  were  o f 11.6 a n d  line  in F i g .  11.3 a n d 15.4  comparisons  could  b e made  Functional  Relationship  tons/ha  using  the  S5  curve.  4.6.2  Yield-Fertilizer One  yield  equation  quantitatively applied Hagin  relate  fertilizer  and Tucker,  exponential originally  (Hagin  be  from  increase  following  when  (x can  functional  dy/dx  =  soil  equation  response  supply from  taken  Where as  relationship  nutrient  or  ( A S A , 1975 a n d  of a plant  or  an  developed  such  in  a s P. factors  yield  nutrient yield  of the nutrient a l l other  i s  of growth  increase  constant,  to  function  t h e maximum  the supply  used  formulation  nutrient,  the  is  growth  (A)  (y)  (x) i s that  increased condition  nonlimiting,  the  holds:  K(A-y)  [4.3]  where: as  to  Mitscherlich  1982) in  >°o). be  frequently  i n h i s law o f e f f e c t s  t o the decrement  indefinitely  been'  growth-limiting  Tucker,  produced  variables  response  The  stated  and  proportional can  yield  yield-nutrient for a single  resulting  has  i s the M i t s c h e r l i c h 1982).  Mitscherlich that  crop  that  A  i s defined  above,  K  i s a proportionality  constant,  1 00  y  i s the y i e l d  x  i s the s o i l - P  By  integration  proportionality  response,  and  supply.  of  the  factor,  above  c  [c =  equation  and  InK = 0.434K],  insertion the  of  logarithmic  form i s  log(A-y)  By  this  asymtotic assumes the  =  logA  - cx  equation,  t o A. that  remaining  [4.4].  as x  I t h a s t o be e m p h a s i z e d  when  only  growth  one n u t r i e n t  factors  increase,  dy,  of  yield,  increase,  dx,  of  the  proportional present  i s successively  to  the  in excess  are  y,  maximum  here  factor,  that x,  constant,  with  limiting  increased,  respect  yield  and y e t not harmful  A  the  becomes equation  i s l i m i t i n g , and the  to the  nutrient  y  differential differential  factor,  (attainable  amount) minus  x,  i s  when  x i s  the  actual  yield. In  practice,  fertilizer, before this  x and the a v a i l a b l e  fertilization,  development  log(A-y)  A  soil  equation  into  = logA  b  (Hagin  Eq.  factor,  the  nutrient and Tucker,  [4.4] m o d i f i e s  from  two  present 1982). i t  sources: the in  the  c  form:  soil  Incorporating  to:  [4.5].  approximation  differentiated  into  (c,) o r i g i n a t i n g  and t h e one coming took  i s coming  - c ( x + b)  subsequent  proportionality the  the nutrient  the portion  from  the f e r t i l i z e r  (c) so that  the from the  101  l o g ( A - y ) = l o g A - ( c x + c,b) The used  M i t s c h e r l i c h f u n c t i o n o r some m o d i f i c a t i o n  for estimating  world.  It  has  fertilizer  been  1982)  to describe  yield  i n the p r a c t i c a l  application. could  as  found  further  that  justify  phosphorus  conditions  the  and T u c k e r , n u t r i e n t and  and  rates  of  t h e c h o i c e of t h i s model, i t  (the test  concept  in soil;  throughout  between a p p l i e d  w e l l as potassium uptake  immobility  thereof, i s  (ASA, 1975 ; and H a g i n  range of s o i l  f o l l o w the M i t s c h e r l i c h  relative  requirements  w e l l the r e l a t i o n  To  be added  study), to  [4.6].  nutrient  patterns due  in  this  by c r o p s a r e s a i d  principally  t h e same i s n o t t r u e  to  their  f o r nitrogen.  Model V a l i d a t i o n . The suffice  model for this  in  the  form  presented i n Equation [4.5] w i l l  paper:  l o g ( A - y ) = l o g A - c ( x + b)  W h i l e Hagin and T u c k e r equation and that  be  Rendig  (1982)  [4.5].  recommended t h a t  t h a t v a l u e o b t a i n e d from s o i l  (1972)  preferred  b be c a l c u l a t e d .  b  in  f r o m b o t h methods s h o u l d a g r e e c l o s e l y  above  a n a l y s i s , Analogides  t h e s t a n d a r d s e t by  To be o f p r a c t i c a l  the  Mitscherlich  —  significance, results  otherwise  i t would  be  difficult  t o a c c e p t t h e a c c u r a c y o f t h e model a s s u f f i c i e n t f o r  predictive  purposes.  To  f i t t h e d a t a t o t h e model i n t h i s a n a l y s i s , c a n d b were  c a l c u l a t e d and t h e l a t t e r  was f o u n d  to  agree  reasonably  with  1 02  soil  test  values  used  for  the  computations  c  =  1/x  log[(A-y )/(A-y)]  b  =  [logA  where  The fitting  (Equation  [4.9]  or  Figure  14).  The  expressions  are: [4.7]  0  y  -  log(A-y )]/c  i s the  0  yield  following and  are  [4.8]  0  obtained  points  helpful  with  should  be  P1  kept  in understanding  fertilizer  level.  i n mind  the  the  in  results  presented  herein: (i)  b,  the  present  in  the  available soil  test  (ii)  A,  yield  amount  in  soil  x  (Table  maximal  obtained  when  was  was  assumed  attaining  the  (iii) and  It S5  was  comparable  except this  P to  only the  i n S1 of  S1  depth  other  from  assigned  the  (irrigation  held  growth was  constant processes  adequate  and  and  yields  S4  (Table  former  plots.  stipulates  a l l one  p r e d i c t i o n s from reliable  the  equation  limiting  concept,  that  levels  when  P  for  A).  more  those  uniformly  average  was  nitrogen  give  Mitscherlich  adopted  that  considered  would  extractable  the  yield  be  adequate  water  and  originally  used.  phosphate  while  unchanged  was  yield  irrigation  to  Accordingly,  potential  and  remained  phosphorus  assumed  V)  schedule i t  or  was  a l l plots.  value  the  of  other  on S4  V)  factors  test. could  To not  S2,  S3  since  the  were  not  Furthermore,  that  do be  model  the  model  be  are  adequate  justice  to  regarded  as  103  adequately XVI  are  test  (0.03N  soil  significant, soil to  P  ppm  XVI , P  added  additional fertilizer soil Table  P  confidence  was  used  directly  the  were  refers  or  prior  to a p p l i c a t i o n  XVI  Comparison  -  FERTILIZER  SOIL  of  TEST  the  to -  soil  soluble  P  loam,  that  MEASURED  was  highly  proportional  the  soil  of  P  test  In  Table  in  soil  the d i f f e r e n t l e v e l s of b  is  P  treatments.  Calculated  ADDED (x-b)  available  P  Yields  CALCULATED  VALUE  YIELD  LEVEL  (ppm)  (t/ha)  (ppm)  (t/ha)  11.5  0  11.5  58=b  for  f r a c t i o n of  TREATMENT  P1  Bray-1  linear  validation.  P-fertilizer and  was  the  amount  before  Actual Cowpea  and  is directly  i n model  the  model.  the  sandy  Table  satisfy  regression  ( x - b ) ppm. of  which  in  established,  to  availability  applied,  of  flouride  this  4)  S5  linear  With  (Column to  HC1)  in this  Ammonium  presented  and  P added  The  i n d i c a t i n g that  the added. in  13).  by  S3  i n 0.25N  a  (Figure  data  in application  NH F  extracted  value  the  stated  r e l a t i o n s h i p between  extractant the  Thus,  a v e r a g e s f o r S2,  conditions  The  irrigated.  YIELD  P2  140  15.3  82  17.2  P3  169  18.2  111  18.0  P4  222  19.3  164  18.8  P5  239  18.9  181  19.0  of  in  104  Figure 13 - Rpplied P as Related to Bray-1 Extractable P  H 0.0  1  i 13.33  1  i  1 1 1  i  26.6 RDDED 6 40 PHOSPHATE. .0 53.33  i  i  Kg 66 / h.6a6  1  i 80.0  i  i 93.33  i  105  Figure 14 - f l i t s c h e r l i c h Equation and Yield Curves - 0 ACTUAL YIELD CURVE CALCULATED CURVE  l o g ( 1 9 . 3 - y ) . = l o g l 9 . 3 - 0.0066(X + 58.6)  64.0  ~i  96.0  r  —i  128.0  160.0  P ADDED TO SOIL (ppm)  192.0  1  224.0  1  1 06  The  equation  logd9.3  It  i s  - y) = l o g l 9 . 3  interesting  sufficiently Table  with  XVI.  and  yields  between  this  yield column  (Hagin  also  then,  the  This  ( 5 8 . 6 ppm)  o f 5 8 . 0 ppm  o f t h e method  agreed  shown  in of  never  that  caused  XVI a l s o .  in by  accordance Analogides  an  reaches  by f e r t i l i z e r  that  ends  as  range  not wide  to capture  means  of  Except  for  P2,  described  Figure  Mitscherlich  the equation  of the y i e l d  does  maximum  (0 - 80  I t must  P 0 ) 2  5  In  general  a s t h e one i n i t  predict  be c o n c e d e d trial  a n d many  to the crop  (5  or a point  here  in this  a c c u r a t e l y , the s e n s i t i v i t y  i s toxic  admit  not f i t data  nor can  of f e r t i l i z e r  kg/ha  to detect  did  curve.  an a b s o l u t e  levels  further  l e v e l - P 5 and r e p o r t e d  f u n c t i o n , such  and  well, range  14  failed  exponential  sufficiently  of P that  by  i n the p r a c t i c a l  herein.  o f an a p p l i e d n u t r i e n t .  were  equation  the equation  unusual  1982)  extreme  the  level  calculated  discussed  Of c o u r s e ,  i s not  1975)  values  in Table  results  Tucker,  level  experiment enough  3.  (ASA,  toxicity  b  [4.9].  t o i t s asymptote  the M i t s c h e r l i c h  result.  at both  question,  i s :  19.3 t / h a , was e s t i m a t e d  a p p l i e d P and y i e l d  depression  and  obtained  —  from  the experimental  clarifies  in  yield  [4.9] are reported  relation  the  curve  [ 4 . 4 ] a n d by a d o p t i o n  theoritical  predicted  of  value  A =  14  + 58.6)  calculated  test  yield",  of F i g u r e  (1972).  The Equation  that  soil  of the y i e l d  Equation Rendig  the  average  curve  - 0.0066U  t o note  T h e "maximum  extrapolation with  describing the y i e l d  levels) zone  at which  1 07  yield  s i g n i f i c a n t l y begins  nutrient,  for  nutrient  Mitscherlich  expanded  to  in  effects the  this P  reason  therefrom worth  that  that  for  of  only  more  be  reduces  result  of  calculated  excess  yield-added  the  in  in  the  whether  compaction,  the  caused  weeds,  relationship  unchanged  and  yield  states:  same  the but,  levels  very  any a  crop) as  amount.  (W1,  W2  The  over  and  factor  the  growth factor  if a  levels  moisture  the  derived  other  in  causative  and  American  Therefore,  sunlight,  to  partly  given  any  variations  subject  and  doubtful  exercise. "  be  because  relationship  be  way  between  time  could  partly  paragraph  (of  by  a  simultaneous  would  same  at  relate  functional  the  nutrients  treatment  rate  radically  It  mathematical  growth  rate  nutrient,  water  1975)  reflected  on  been  variables.  preceding  purposes a  more  to  any  (ASA,  the  occurs,  remain  of  recent  or  water  three  than  essential  should  a  and  of  two  too,  the  predictive  Agronomy  must  reduction  in  reliability  decreases  period  as  production  irrigation  were  has  only  situation  and  little  Society  not  crop  stated  there  the  equation  other  of  because W3),  experimental  incorporate  several  applied  of  the  decrease  curves.  The  but  both  to  agents same  rate  of or  and  an soil  growth  mathematical  treatments." Thus, yield  (Eq.  relationship 4.5)  would  prediction,  the  Stewart  4.2)  and  between be and,  the P  model  for  relating  Mitscherlich added  accepted because  as of  and  the  function  cowpea  adequate  irrigation  dry for  limitations  water  describing  matter the of  yield  purposes the  to the  (Eq. of  experiment  1 08  being  reported.  factors this  with  crop  purely  the and  borne  mind.  in  experiment predict  of  the  effects  the  and  treatments  on  of  subsequent arriving  site  statements models  in  While  separate cowpea  this  With been  be  of  yield  made  but  i n f l u e n c e s of i n view  as  the  must  quantitative frequently  obtained  the  can  two  of  the  presented  in  for  conducted,  be  from be  and  phosphorus  growth  levels  was  irrigation  and  these  experiment  validations  effects  factors  of  recommended  information  predicted, particularly  variance  their  section  model  crop  analysis  the  would  the  combined  between  at  where  subsequent  the  interactions  could  aim  qualitative of  has  a  the  treatments  easily  In  this  used  phosphorus  content,  effects  highly the  to  are  the less  significant analysis  of  tables. this  treatment,  addressed  allow.  to  the  the  f o u r t h o b j e c t i v e of  extent -~  that  the  this  experimental  thesis data  1 09  V.  5.1  SUMMARY  AND  CONCLUSIONS  Summary An  cowpea  irrigation-ferti1izer ( Vigna  British source  Columbia  the  and  design  experiment  an  plant  weeks  procedures moisture to  whether  or  the  aid not  in  any  plant  per  yield  after  90  days  fertilizer  the P  to  the  returns."  A  plant  and of  the  where  response  leaf  on  weekly  a  taken and any  taken  line-  the  size  purpose  of  the  this  crop  water crop  to  regimes  is  number,  rarely  found  but,  provide water  —  for  first  gravimetric the  soil  cropping  indications  the  seven  plant be  as  to  and  hence  weeks  stated  the not  foliage  in parallel  The  r e g r e s s i o n f i t was  the  cycles.  of to  height  scheduling  deficit  dry  curvilinear  M i t s c h e r 1 i c h ' s model  basis  throughout  literature. was  plant  Irrigation  during  content  were  curve  a  and  of  the  were  irrigation  nutrient  quoted  from  of  considerations  irrigation  interval-type,  data  growth  linear  response  emergence.  were  of  University  applied  The  with  band-applied.  scheduling  part  the  characteristics  the  made  rigid  response  the  in  was  conducted  iterative  area.  plants experienced  above,  reported  system  seedling  were  during  The  nicely  P  determinations  season  stress  nodes  after  with  different  measurements  of  was  environment  Fertilizer  number  seven  under  ecological  The  Water  designed  determine  fertilizer  cultivated.  on  experimental  to  was  Walp.)  farm.  irrigation  the  was  phosphorus  and  lateral  desirable of  [L.]  research  sprinkler  of  in  unguiculata  experiment  with  matter  (convex)  "law  harvested  of  data  yield-  and  fitted  diminishing  necessary.  However,  110  in  fitting  (1977) of  the  y i e l d - s e a s o n a l water  yield-evapotranspiration  both  model  predictions  validations  under  a  specifications. irrigation  water  and  model.  There  designed  so  that  functional  of  any  test  be  that  to  Extrapolation another  was  optimum  (irrigation the  study, the  applied less  as  water  given water  within left for  the the  given  other  soil  found in  by  advantageous  level, was  water  persistently  was  cycle  excessively  under  for  this  was  likelihood quantities  levels  S)  might  conditions. that  is  matter,  necessary water  irrigation  of was  the  of  because  interval  and  this  critical water with  addition  to  schedules  at  saved  Irrigating  wet;  In  frequently in  evidently  (e.g  could  irrigation  more  for  supply  season  crop.  important  normal  increased.  irrigation  yield  the  amount  to  fitting  multivariate  the  total  irrigating  comparison  efficiency normal  the  for  experimental and  yield  management  these 5  in  experiment  of  and  the  rainfall  set  W,  Curves  limited.  requirement  Reducing  tool  a  the  with  irrigation  during  of  to  taken  crops  rainfall)  irrigation  depressed  of  though  fertilizer  the  range  even  plot.  yield  levels  that  water  be  Stewart  useful.  data  that  examined  3  the  agronomic  truth  could  to  useful  enough  i s consequently,  yield  was  use  P,  a  jointly  the  levels,  distribution  per  improving any  the  seasonal  control  P  account  levels  plus  the  not  denying  demonstrated  cowpea  of  relationship  environment  It  in  no  (5  to  set  was  data  i t became  be  fertilizer  proper  variables  limited  exceed  is  model,  could  given  There  use  (Table  three  XV)  times  every  3 days  in  this  partly  accounts  scheduling  technique  July)  '(S3).  111  High  frequency  regard limit  to  irrigation,  water  exists.  For this 4 days  (every  design  consumptive  Methods  for determining  optimum this  factor  limiting  erased  of  late  Spring  irrigation  irrigations  i s  efficiently. supplies  under  these  leads more  to late  obviously  critical  how  frequently  with  essential,  Scheduling  irrigations  in  investigated  in this  would  applied design  only  when  irrigation  significant  rains  work  necessary depth, and  be  such  ensure  as  room  maximizing  to  number these used  on s o i l  water  when  to  irrigation set,  the based  probably cases,  safe on  side. concepts  irrigations  some  an case  be  This  that  just  In  the  a  t o be  a n d i n some  on  areas  and with  thereby  i s  at each  to  i s the  deciding  water  P  matter  to apply  difficult.  to  leaving  as  information  more  dry  water  varies  water  to apply  any  appeared  (such  as t h i s ,  be v e r y  to irrigating than  of  the  findings.  o n when  i f  such  water  c o n d i t i o n s must  farmers  aid  studies  much  decision  at  procedure.  i n Vancouver)  the  half  irrigated  o f cowpea  rainfall  required,  the  be  these  scheduling  but, a  consideration.  irrigation  response  Summer  with  maintaining  from  of  uncertain  Without  and  use while  of factor,  where  under  with  irrigating  yield  should  developed  yield  and c r o p - s o i l  irrigate  water  the importance  the  area  are  cowpeas  further  by t h e e f f e c t  irrigation from  study,  maximum  yield  S5,  site,  the interval  gave  plots  when  in  c a n be  within  opportunities  improving  on t h e t e s t  a l l treatment  reductions  many  besides  (43mm/day)  use  when  In  crop  in July)  level,  yield  offered  conservation  twice  achieve  thus,  fraction  for the  are  of the  sporadic efficiency  yet of  112  irrigation As well  to  might  level  of  potential For phosphate  and  P  optimum  a l l  plots  irrigated,  and  the  the  of  of-growth Some  fact to  need  plot  at  (S4)  deductive  fertilizer  data  recommendation  as for  lower  any  the  former  two  data  conditions  maintaining  obtain  at  a l l P  the  over  a  yield  once  control P  P  namely,  P1  that  close,  contemplated, is  addition in  to  the  and  to  be  ensure  superior  the  stage-  level.  could  basis  plants  nutrient.  crop  (S1)  kg/ha  than  quite  is  is noticeable  the  50  observed  were  fertilizer  specified  forage  of  i t was  irrigation  fertilizer;  as  and  same  levels  levels  i f no  0  the  Furthermore,  conclusions a  respond The  in quantity  of  apparent  plots  of  schedules),  phosphorus  irrigated  to  kg/ha  apply  becomes  importance  80  that  for  to  phosphorus.  order  was  low.  to  found  moisture.  that  control plot  yield  climatic  70,  markedly  need  the  (irrigation  the  i s no  with  in  soil  was  soil-crop-climatic  report  forage  60,  legume,  the  fertilization  were  pointing  yields  i t did  a  soil  to  indications that  in  optimum  but  with  P2,  there  of  limited  produced  are  yields  being  be  with  fertilized These  cowpea  fertilization  question  high  usage.  expected,  obtained in  water  be  for  drawn  from  the  phosphorus  production  from  yield-  fertilizer  cowpea  in  this  situation.  Referring P-Uptake difference scheduling  by  to  the  cowpea,  between  P4  regimes,  tables i t and the  and  graphs  is clear P5  —  latter  on  that in P  dry  there  three level  was  matter i s no out less  yield  and  significant  of  the  five  productive.  113  From  an  have  agronomic  been  the  detrimental  to  point  toxic the  of  view,  level  crop.  at  least  Economically  level,  the  crop  produce  more  dry  matter  plants,  i t  is  not  economically  on  environmental  phosphate. that  Based  application P  lot  of  of  application  fertilizer  or  and  P  as  in  subdrain  low  this  deductive  statements  P3, an  P4  optimum  under  the  as  P4  (30.6 level  35  the  15-25%  from  1982) to  Crop  a  low but  of  crop-soil  fertilizer  kg/ha for  in  a  source  for  data  phosphate)  studied.  can  obvious a  some  of  applied  and  Tucker,  (William,  with of  be  runoff  pollution foregoing P5  as  an  comparable  yields  cowpea  in  or  rejecting  higher  kg/ha  form  suggest  irrigated  80  site  The  not  level  at  soil  carried  can  P4)  Hagin  location.  basis  P4  result  than  be  significantly  70  situation  mobility  this i t  i t is  recovery  can  but or  to  applying  yield  and  at  that  will  must  reactions  since  up  (P5)  1972;  P5  soil  a p p l i e d monocalcium  and  P  P  higher  experimental  kg/ha  least  kg/ha  Since P5  up  justifiable  farm no  that  convincingly  constitute  the leave  i t set  at  (Veits, has  said  considerations,  thereof.  Tucker,  remote  P  (without  discharges  between  as  element  and  level.  absorb  be  speaking,  indicate  much  soil  elsewhere  yields  or  either  is a  Hagin  excessive  not  products  while  1971  of  residues  transformed  1982)  did  or  i t could  than  P1  considered production  114  5.2  Conclusion It  must  be  reiterated  was  supplementary.  on  irrigation  for  the  presence  fertilizer,  data  of  of  The  The  The  Allow  does  not  Give  select  of  results  irrigation  this  study  dry  plots  dependence  matter  yield  in  important.  The  responses  from  growth  supports  study  plant  became  plant  the  the  view  water  i s more  the  total  quantity  may  be  that  important  the in  used.  acknowledged  from  two  results  the come  the  farmer  to  regularly  farmer  the and  yield  maximum  optimum  estimate  during  the  energy,  fertilizer or  f o r optimum  than  on  indicated  irrigation  of  of  irrigation  data  but  i t s productivity  perspectives:  2*  analysis  importance  1*  the  beneficial  application  determining  of  growth,  demonstrated  irrigation. time  None  that  the  yields growing  management water  if  season  or  alternatives  application,  levels  rainfall  that  phosphate  should  production levels  of  to  produce  cowpea  on  his  farm.  Poor  rainfall  evapotranspiration of and  most humid  Rainfall disrupts full  soils  occurs any  distribution  cause  areas,  and  irrigation  particularly sporadically  preplanned  irrigation  distribution  schedule  regime.  In  with  low  to  be  in  water-holding needed  i n many  intensive  during or  respect  the  falls  order  to  a  make  capacities semi-arid  agriculture.  growing few  to  days  season after  effective  use  and a of  11 5  rainfall  that  important will a  that  hold  reasonable  evidence with  designed  For  P  combination  of  5.3  yield  cowpea  with  relationship fertilizer  exists  i s  between  investigations  f o r the  inclusive.  and schedule, the  optimum  the best  cowpea  dry  P.  the performance  irrigation produce  management  the  following  and  complex  practices of  efficient  and this  of developing  t o more  of  yield.  a  understanding  i f the objective leading  water  maximum  that  i s t o be a c c o m p l i s h e d . in  the  f o r a s e t time  produce  illustrate  better  practices  P and water  will  water  A  half  5.1, a n d under t h e  to ascertain  that  experiment  important  management  fertilizer further  the  the  irrigated  i s  i s 30.6 kg/ha  optimizing  levels  response.  relationship water  of  of  hold  Studies  was u n d e r t a k e n purpose  be  of 9 days  will  utilization  f o rFurther  This  amount  for  to  percolation  the crop  in section  variables  the s o i l  investigation,  interval  that  than  deep  (1.7 i n . )  of i r r i g a t i o n  i t i s  be room  t o September,  requirement  fertilizer  results  o f 43.18mm  of June  and f e r t i l i z e r  the  this  i s that  irrigation  production  study  phosphorus  and  level  without  in  already discussed  Recommendations This  The  months  will  set of 3 hours.  depth  recommendations  fertilizer  used  season,  be a p p l i e d  so t h e r e  the study  and an a v e r a g e  reasons  water  zone  cowpea from  irrigation  rainfall  per i r r i g a t i o n  cropping  preceding  matter  of  application  6 hours  relevant  amount  generated  the  irrigation  the rooting  For the  21.59mm  during  less  within  occurring.  of  occurs  use  soil of  In t h i s  respect,  directions  become  116  imperat i v e :  1. of  It  i s n o t known  the s o i l  and p l a n t  indicators  of  applicable  as  i t  in this  present  t o be made.  i s  that  conditions vary.from  know  the  combinations future go  a  from  since  years.  long  way  Both  the experiment  2.  The  yields  of  treatments was  with  increased  reliability number to  temporal  so  secondly,  of  within  recommendations reason,  different are  namely,  usually  to  treatment made f o r  repetitions  t h e scope  coordination was  would  o f i n f e r e n c e made  and  resulting  are suggested:  the present  irrigation  of  by  when  either  variable  improve  the  experiment,  first,  of  50  the a  i t i s necessary  irrigation  range  frequency  further of  and  comparing  irrigation  To  of i n f e r e n c e  number  of  demonstrated  independently.  of refinements  environmental  far.  the y i e l d s  the  the  similar  i t i s important  and s p a t i a l  fertilization  and scope  increase  on  improving  practices P  to year,  recommendations  necessity  fertilization  year  are  a s i n many  evaluate  f o r which  as  environmental  i n the different area  levels  yield  Consequently,  f o r an o b v i o u s  years  towards  and  to  the  established  optimum  soil  important  in this  whether  were  and  other  study,  of  which  Columbia.  Likewise,  effect  studies  need  in  British  experiments,  conditions are  irrigation  in  treatments  these  parameters  f o r cowpeas  conditions field  from  water -  70  levels; kg/ha  of  117  phosphate, of  the  and  lastly,  incremental  rate  kg  implemented  in  10  increase  but  the  suggested time  the  number  specified  of  replicates.  fear  studies.  are  important,  limited  and  improve  and  made  being there  the  hence  the  5  kg  instead  reported is a  by  the  experimental  feasibility  of  to  these  funds  compactness  now;  need  Unfortunately, largely  experimentation; system  be  study  least  irrigation  this  suggested  for  the  the  refinements  available  reduce  not  should  of  and the  design these  1 18  LITERATURE  CITED  A l l e n , W.H a n d J . R . Lambert, 1971. A p p l i c a t i o n of the p r i n c i p l e of c a l c u l a t e d r i s k to s c h e d u l i n g of supplemental i r r i g a t i o n . I. Concepts. Agric. 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Use of p h o s p h a t e s o r p t i o n i s o t h e r m s t o p r e d i c t t h e phosphorus r e q u i r e m e n t f o r cowpea. Tropical Grain B u l l e t i n No. 21 : 1 0 - 2 1 . S h a n t h a k u m a r i , P a n d S.K. S i n h a , 1972 a n d P h o t o s y n t h e t i c a 6:185, 1972. P r o c , S e c o n d SABRAO, New D e l h i , 1973. S h o u s e , P., S. D a s b e r g , W.A. W a t e r d e f i c i t e f f e c t s on use of cowpeas. Agron. S i e g e l , S., 1956. Non-parametric s t a t i s t i c s M c G r a w - H i l l Book Company,  Soil  188:604-  Legume  1973.  J u r y , a n d L.H. water p o t e n t i a l , J. 73:333-336.  Stolzy, 1981. y i e l d and water  for the Behavioral Sciences. T o r o n t o , New Y o r k a n d London.  S i n h a , S.K., 1977. P h y s i o l o g i c a l a s p e c t s of y i e l d improvement in grain legumes. I n : F o o d Legume C r o p s , I m p r o v e m e n t a n d P r o d u c t i o n , FAO P l a n t P r o d u c t i o n a n d P r o t e c t i o n P a p e r 9, Rome.  No.  S l a t y e r , R.O., 1969. I n : P h y s i o l o g i c a l A s p e c t s o f C r o p Y i e l d , by J . D . Eastin, F.A. H a s t i n s , G.Y. S u l l i v a n a n d C.H.M. Van Bavel, (editors). Amer. Soc. Agron. Madison, Wisconsin. S n e v a , F . A . , D.A. Hyder and C S . Cooper, 1958. T h e i n f l u e n c e o f ammonium n i t r a t e o n t h e g r o w t h a n d y i e l d o f c r e s t e d w h e a t g r a s s on t h e O r e g o n h i g h d e s e r t . Agron. J. 50:40-44. S t e e l , and T o r r i e , 1983. P r i n c i p l e s and P r o c e d u r e s of S t a t i s t i c s . McGraw-Hill C o m p a n y , I n c . , New Y o r k , T o r o n t o a n d London.  Book  1 24  •Stegman, E.C., J . T . Musick and J . I . S t e w a r t , 1980. I r r i g a t i o n Water Management— C h a p t e r 18 i n M.E. 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J . , P.A. Huxley, P.J. D a r t and A.P. 1976. Some e f f e c t s o f e n v i r o n m e n t a l s t r e s s o n s e e d o f Plant and S o i l 44:527-546.  Huges, cowpea.  S u m n e r , M.E a n d F . C . B o s w e l l , 1981. Alleviating Nutrient Stress. I n : A r k i n , G.F a n d T a y l o r ( e d s . ) ; M o d i f y i n g the Root Environment to Crop S t r e s s . A S A E M o n o g r a p h No. 4, S t . J o s e p h , 49085.  H.M. Reduce Michigan  T e w a r i , P.G., 1 965. E f f e c t s of n i t r o g e n , phosphorus and p o t a s s i u m of cowpea. Expt. Agric. 1:257-259.  nodulation  on  T e w a r i , P.G., 1966. . E f f e c t o f p l a n t i n g d a t e on n o d u l a t i o n a n d d r y m a t t e r of cowpea i n N i g e r i a . Expt. Agric. 2:45-47. Turk,  K.J and A.E. Hall, 1980. Drought a d a p t i o n t o cowpea: 72:413-439.  Papers  I-IV, Agron.  yield  J.  U n g e r , P.W., H.V. Eck and J . T . Musick, 1981. Alleviating P l a n t Water S t r e s s . 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Irrigation Science 3:247-257.  APPENDIX A - METEOROLOGICAL DATA USED IN IRRIGATION DESIGN  UBC., Vancouver Weather Sta t i on , Lat. 49 15 r , Lone . 123 15 W, 87 m.  (1951 - 1980 Normals)  JAN  FEB  MAR  APR  MAY  JUN  JUL  MAX. TEMP.  5.1  7.7  8.8  11.7  15.2  18.1  20.7  MIN.  0.6  2.5  3.0  5.2  8.3  11.4  DAILY TEMP.  2.9  5.1  6.0  8.5  11.8  RAINFALL 152.3 126.7 112.0 68.9 59.5 SNOW 20.5 6.1 4.0 0.2 0.0 TOTAL 172.8 132.8 116.0 69.1 59.5  SEP  OCT  NOV  DEC  YEAR  UNITS  20.3  17.5  13.1  8.6  6.3  12.8  °C  13.2  13.2  11.1  7.5  3.7  2.0  6.8  °C  14.8  16.9  16.8  14.3  10.3  6.2  4.1  9.8  °C  43.0 0.0 43.0  37 0 0 0 37 0  52.5 0.0 52.5  72 .2 133.4 158.4 187.1 1203. 0 0 0 0.0 3.1 20.8 54. 7 72 .2 133.4 162.5 207.9 1257. 7  Vancouver International A i r p o r t , B.C. Lat. 49 11 N , Long. 123 10 W, Elevation REL. HUMID.  80  78  72  68  65  66  AUG  3m A l t i t u d e 65  68  (1951 - 1980 72  78  72  mm mm mm PRECIP.  Normals) 83  73  VAPOUR PRESS. 0.68 0.77 0.78 0.89 1.09 1.31 1.51 1.55 1.39 1.13 0.86 0.77 1.06 SEA-LEVEL PRESS.101.64 101.67 101.61 101.7 101.7 101.7 101.8101.7 101.7 101.7 101.7 101.6 101.69  %  OO 00 _J C3 •Z.  KPa KPa  0 0  >> — s  CC  o o  UJ  o o  •  cc c o  Source: Canadian Climate Normals, M i n i s t r y of Environment, Ottawa.  127  APPENDIX B -  CATCH CAN LAYOUT FOR WATER DISTRIBUTION TEST  3.66  m  2.74 m  CATCH CAN  - SPRINKLER LATERAL LINE  * *  Evaporation losses were n e i t h e r c o n t r o l l e d nor measured. S p r i n k l e r operation during the t e s t (and Experiment) was 206.7 K P a  128  APPENDIX B c o n t d . S P R I N K L E R UNIFORMITY  TEST  RESULT  Time of catch = 50 min Diameter of can = 10.5 cm  SPRINKLER  13  76  205  205  202  225  118  22  11  100  285  316  305  305  175  28  10  155  300  300  275  275  168  61  .22  154  225  966  648  174  156  68  244.25  154.25  44.75  2.83  1.78  0.52  IRRIGATION LINE-SOURCE MEAN VOLUME OF CATCH(ml) DEPTH OF WATER CAUGHT/can  (cm)  IRRIGATION DEPTH FOR TIME SET OF 6hr. (mm)  169.8  106.8  31.2  W3  W2  Wl  SPRINKLER COEFFICIENT OF UNIFORMITY ( C h r i s t i e n s e n , 1942) =  48%.  (Note that there was no l a t e r a l o v e r l a p , t h e r e f o r e , the c o e f f i c i e n t of u n i f o r m i t y given above i s apparently the water d i s t r i b u t i o n pattern p e c u l i a r to the system).  APPENDIX C - PLANT ANALYSIS: AUTOANALYSER PLOT  AUTO ANALYSER N AND P DATA  APPENDIX D UIC  rO«IIT  N*triCB ANO N  N  ICIll  LAIOHATOAT - AUTOAMAITIIH  t,.w tot. l»1  N AND f DATA  0*T« ICT: h T H H l l H I  I H A I C A T I O N  » :  INI :  T H C A Tn tNT t  41.11; If I :  M I 4 I N I m r » u i N T ) o t . ( i rrn tHC t*nrn % N ( I N %r i t *0 L I  & I  SOLID  i i o .  %tri  • Ann.  I . I  CB  I . I I  •  i . eoo •. n o 1.601 i .oe«  LAIOAATUAT  100. 100.  1 0 0 / 1 0  1 10  I 1 1  1 0 0 / 1 0  • * *.*  .10  .414  .11)  . t »  II  0  . SO 0  VATt»  .10  0  4  . 1 0 1  .10  1  .111  . u e .10  1  . 1 * 1  I.  .001  AWTOAMAL1SIK  10 0. I  M AND t  PAT*  .  tut R C M I C N T loo.oo r r n N i a n A M P a n m r K i i t K T rrn H rrn r lAnri SAnrLC wt U H « U N tOLM. IOLM. ttAII IOL101 101101  lo.io r r n mniKT t t n rL H mil VOL. NT  • n * NO rrn i tOlM.  IOILI  AHAbtit* DATA SET: KTI«#«»«t*l f of.w H IAR1C AT I OH TKIATHtNTS •H I : 41 . 00 J INI : i t . I H If I :10.06] If 1: I i . i n n r l : 0.16; I I M :  80 ,  106.  10  WATER  J11  1. M l I . Ill 1. I l l 1.0*1 4.111 * . IM I . tl I 4.111 I . 0••  .14  1  1 TT . 1 141.1 It . T it•. I 110.1 411.1 «Tt . 4 If 1 . I 4 1 1 . 1  . T T T . 1 6 1 1 1 4 . 1  .Tit .111 .10 1 .1*1 .6*1  4 1 1 . 1  414  . 1  4 1 1 . 1  111  . 1  0. I  ii.  I I I .100 I . 000 ii.li I .01* T I . II I . 610 li.ti 1 . Ill T I . 11 I . Ill I T . 4 I I . 000 II . IT I . I l l I I . IT 1.001 T» . TI I . 111 11.11 I . 010 11.11 I.Ill 1 I . »» 1.610 Tl.lt I . 000 4f . II • Til 11.14 I . on IT . 4 4 1 .600 .11 I . Ill  il:ii  i  16.06 r r n r **nr*. . I I rn VOL. I'T 1 0 0 . 0 0  166.00 100.06 I66.0O  16 .60 11.11  1 0 0 . 0 6  100.66 110.06 116.66 1 0 0 . 0 0  166.66 106.10 160.00 100.00 I I I . 11 100.06 116.00 106.66 116.60  10.10 ll.lt 10.10 Tl.lt II . 10 10.06 40.00 14.00 41.00 T0.lt 11.61 11.10 11.61 1 4 . 06 41.10 IT . 10 4 1.16 I .16  WIC fORtlT I 0 I L 1 LA I OH ATOM 1 . AVTOANA IT11» H ANO t DATA ANAlTItH 0 ATA i ( T ; MTK0414I01 r A N D M IHMICATION THC ATntN.Tl »Nl (4.16; SN1 : 41.10; * r I : It :  VIC •ri:  ll.ll;  >N1 I IN) A t f A l l t N T 111.61 r m N ; • r i A N D i n LINI wnrit \ H I I N sr * I N rrn H 10 L I O I 10 L I 0 I • OIH. 114. M O .  . 1  tT  .14*  .Til . 060  111.4 111 . I 4*4.4 4IT , I 410.1 10 f . T 111 . I 411.4 111 . I 40 1 . T • TO . 1 JIT . I 114.0 I.I  »iri  »6M  MriINT I Ann. ftAlO 1.106 1.606 I . Oil 1.16 0 t . 666 1.660 1.000 1.060 1.000  I . I 0 0  1.600 1.006  1.060 1.10  4-  r ANO H 1ARICATIOH. TJtfATHCHTa  100 .  too.  160 .  1 I 1  100.  VATCA  101.  160.  I.06O  rOHIAT BO IL ft LAlORATORT - A V T O A N A L f X t h M AHD t DATA  ANA L T 1 [ftDATA 6 IT : fTTI 4 I 11 4 I 0 I  too. too.  106.  1.000  . II  100.  100.  1.000  I  4I.S0> » M i t . i l l a n : IT.toi t o r n t.ii* tarn I H I t I N I A C f M c i t N T l i t . o i r r n H ia n A N O a n a i r R t a i K T I I . O O r r n l l N t lAnrit %H I I N %r i I N rrn N r r n r l A n r t •Anrt N aOLN. • O L N . riAta VOL. NI TT  166 .  1.066  :  1.111 I • 11 I 4.111 1 . 711 I . I II 6.666 6.011  .111 .Til .ITT .TOT  S  .171  1 1 1 . 1  0.100 t. Ill  11  .I  4 1 1 . 1 4 1 1 . 1  • T T  .I  •. • 0.0  1 . III I.Ill  111.01 .100.00  I . 010 I . 010 1 . lit  110.11 110.00 1 0 0.00  1 . Oil  1.010  166.00  1 0 0 . 1 0  NT  TT . 10 41.11 4 1.11 TI.00 41.10 11.11 14.11 IT.II 14.10 1f.II I.10 I . It I . II t . It  CO  o  131  APPENDIX  E -  SOME G R A V I M E T R I C M O I S T U R E D E T E R M I N A T I O N R E S U L T S  0 cm  „  S.S  S o i l samples were taken with an auger . Sampling depths: 0-30cm 30-60cm.  30 cm — /  Gravimetric s o i l moisture contents recorded as %  60 cm  PLOT I  PLOT IV  PLOT II  July 4 t i . jRRIGATION ' WI Whole p l o t i r r i g a t e d to F i e l d c a p a c i t y . Note special l a t e r a l movements made to ensure ' o v e r l a p ' along the main. 0 -30 cm 30 -60 cm  I  W2 W3  W3 W2  WI  J u l y 3th s I r r i g a t i o n to f i e l d c a p a c i t y .  32.61 30.25  15th J u l y , 3 days a f t e r the rains from 10 to 12th J u l y 1983. 0 - 30 cm 30 - 60 cm  35.47 33.20  36.18 30.68  34.81 29.31 July 25th:  26 - 28/7 0-30 30-60  rai n 47.70 50.60  Showers on 2/8 29.37 36.07  50.60 49.18  40.6 50.6 40.55 33.8 36.5 38.4  Irrigation. 51.37 35.5  45.46 44.6 40.5 36.9  Moisture determinations on the f o l l o w i n g day - 3/8. 31.50 28.67 29.92 28.86 29.2 30.6 28.5 40.14 35.82 34.63 35.51 36.11 35.4 35.0  Before i r r i g a t i n g other p l o t s on 6/8/83. 28.06 28.51 30.78 34.19  A f t e r i r r i g a t i o n on 6/8 49.7 48.7 52.7 52.7 49.143.0 50.1 50.6 50.8 48.4 51.6 48.8  No r a i n since August 2nd .  Before i r r i g a t i n g 24.20 25.14 26.5 28.0 29.8 30.7 After i r r i g a t i o n 34.2 35.1 35.6 30.0 31.7 38.4  20.58 25.44  22.48 28.93  on 14/8/83. 25.5 23.1 24.8 30.9 30.1 31.0 36.9 31.2 33.34 36.7 -33.0 34.3  132  APPENDIX  E  contd.  PLOT III WI  PLOT V  W2 W3  W3 W2 WI  WI  W2 W3  W3  J u l y 15th, 3 days a f t e r rains of J u l y 10-l2th 32.11 35.76 30.76 34.80 33.85 32.30 Before i r r i g a t i o n of plots III and V on J u l y 22nd 25.4 26.0 25.1 25.9 28.53 29.6 29.4 27.7 30.9 28.1 26.7 26.7 30.4 28.5 31.7 30.4 31.7 34.5 A f t e r i r r i g a t i o n of 33.1 39.2  34.6 38.9  30.3 39.7  W2  WI  32.86 34.80  29.2 30.1  30.3 33.5  29.7 32.6  44.5 40.0  36.6 38.9  31.5 39.6  both plots on the same day.  31.0 35.0 39.3 30.3  32.3 30.5  31.1 27.3 32.9 30.4  21.35 30.80  40.4 42.5  28.23 32.45  32.9 36.6 43.8 38.6 3 9 . 1 4 0 . 5  July 25th, 1983. Before i r r i g a t i o n 20.8 30.1  28.1 31.7  30.6 34.7  After i rrigation 28.1 32.8 39.1 33.81 31.7 42.5  33.7 34.8  P l o t V not scheduled to be i rrigated.  Note: Appendix E i s only i l l u s t r a t i v e and not the whole bulk of g r a v i m e t r i c s o i l moisture determinations c a r r i e d out during the experiment. Whenever there was a r a i n f a l l event, s o i l sampling was implemented by taking samples from two depths and on e i t h e r side of each l a t e r a l set i n any p l o t ; however, when a p l o t was i r r i g a t e d , i t was necessary to estimate s o i l moisture contents at WI, W2 and W3 on both r e p l i c a t e s of a p l o t (Figure 4 of Chapter 3 ) .  


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