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Development of a climate-based forage growth model for a Peace River community pasture Wallis, Charles Hubert 1981

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DEVELOPMENT OF A CLIMATE-BASED FORAGE GROWTH MODEL FOR A PEACE RIVER COMMUNITY PASTURE by CHARLES HUBERT WALLIS B.Sc.,The U n i v e r s i t y o f B r i t i s h C olumbia, 1977 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department o f S o i l S c i e n c e We a c c e p t t h i s t h e s i s as co n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA A p r i l 1981 C h a r l e s Hubert W a l l i s , 1981 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e head o f my department o r by h i s o r h e r r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f Spd SdWlCl The U n i v e r s i t y o f B r i t i s h C o l u m b i a 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 ABSTRACT Based on p e r i o d i c c l i p p i n g o f a f e r t i l i z e d p a s t u r e p l o t i n t h e Peace R i v e r r e g i o n i n 1977 and 1979, accumulated d r y m a t t e r p r o d u c t i o n o f a t i m o t h y , r e d f e s c u e and a l s i k e c l o v e r mix was found t o be l i n e a r l y r e l a t e d t o accumulated t r a n s p i r a t i o n d u r i n g the a c t i v e growing season, w i t h a g r o w t h / t r a n s p i r a t i o n r a t i o o f 0.026 t ha V(mm H 2 ^ ) -The e f f e c t o f f e r t i l i z e r l e v e l and c u t t i n g management on d r y m a t t e r p r o d u c t i o n i s d i s c u s s e d . Energy balance/Bowen r a t i o measurements o f evapo-t r a n s p i r a t i o n (E) i n 1977, 1978 and 1979 showed t h a t daytime E can be c a l c u l a t e d f o r energy l i m i t i n g c o n d i t i o n s u s i n g the P r i e s t l e y - T a y l o r f o r m u l a w i t h a = 1.26 + 0.05. Daytime ne t r a d i a t i o n r e q u i r e d i n t h i s f o r m u l a was e s t i m a t e d t o w i t h i n 15%, u s i n g the I d s o - J a c k s o n longwave r a d i a t i o n e q u a t i o n and d a i l y s o l a r r a d i a t i o n d a t a from a r e g i o n a l c l i m a t e s t a t i o n 50 km away. D u r i n g w a t e r s u p p l y l i m i t i n g c o n d i t i o n s E was found t o be l i n e a r l y r e l a t e d t o r o o t zone water s t o r a g e . Root zone d r a i n a g e was found t o be n e g l i g i b l e i n t h i s s o i l , w h i c h has a h i g h b u l k d e n s i t y s u b s o i l . . A s i m p l e model f o r c a l c u l a t i n g t h e c o u r s e o f p a s t u r e growth d u r i n g t h e growing season a t Sunset P r a i r i e Community P a s t u r e i s d e s c r i b e d . The model i s composed o f a s i n g l e -l a y e r r o o t zone w a t e r b a l a n c e submodel and a r e l a t i o n s h i p between d r y m a t t e r p r o d u c t i o n and t r a n s p i r a t i o n . The water b a l a n c e submodel e s t i m a t e s d a i l y t r a n s p i r a t i o n and r e q u i r e s d a i l y v a l u e s o f r a i n f a l l , s o l a r r a d i a t i o n and maximum and minimum a i r t e m p e r a t u r e . I t a l s o r e q u i r e s c r o p a l b e d o and an e s t i m a t e o f t h e i n i t i a l r o o t zone water s t o r a g e . E s t i m a t e s o f r o o t zone water s t o r a g e d u r i n g t h e t h r e e g rowing seasons agreed w e l l w i t h g r a v i m e t r i c and n e u t r o n m o i s t u r e probe measurements. The model, u s i n g t h e above g r o w t h / t r a n s p i r a t i o n r a t i o , was found t o e s t i m a t e hay growth d u r i n g t h e d r o u g h t y growing season i n 1978 t o w i t h i n 15% o f measured v a l u e s . An e f f e c t i v e g r o w t h / t r a n s p i r a t i o n r a t i o of 0.013 t ha "''/mm was r e q u i r e d t o a c c o u n t f o r t h e growth o f p a s t u r e s u b j e c t e d t o a s i m u l a t e d monthly g r a z i n g r o t a t i o n . - i v -TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS i v LIST OF TABLES v i i i LIST OF FIGURES i x LIST OF SYMBOLS x i ACKNOWLEDGEMENTS x i i i CHAPTER I . INTRODUCTION 1 CHAPTER I I . TRANSPIRATION AND GROWTH RELATIONSHIPS AT SUNSET PRAIRIE PASTURE . 5 A. INTRODUCTION 5 B. BACKGROUND 8 1. C a l c u l a t i n g E v a p o t r a n s p i r a t i o n . . 8 a) Energy - l i m i t e d e v a p o t r a n s p i r a t i o n 8 b) S o i l - l i m i t e d e v a p o t r a n s p i r a t i o n 10 2. E s t i m a t i n g T r a n s p i r a t i o n 11 3. R e l a t i o n s h i p Between Growth and E v a p o t r a n s p i r a t i o n 13 a) P h y s i o l o g i c a l b a s i s f o r t h e r e l a t i o n s h i p 13 b) E x p e r i m e n t s u p p o r t f o r t h e r e l a t i o n s h i p 14 C. EXPERIMENTAL PROCEDURE. 17 1. E x p e r i m e n t a l S i t e 17 2. Measurements 21 - v -a) G e n e r a l program 21 b) Forage growth 21 c) S o i l m o i s t u r e 22 d) R a d i a t i o n 23 e) S o i l h eat f l u x 24 f ) Bowen r a t i o 25 g) Data r e c o r d i n g 26 h) Other m e t e o r o l o g i c a l measurements. . . . . .27 i ) C a l c u l a t i o n o f e v a p o t r a n s p i r a t i o n 27 D. RESULTS AND DISCUSSION 30 1. P a s t u r e E v a p o t r a n s p i r a t i o n . . . 30 a) Energy b a l a n c e 30 b) E n e r g y - l i m i t e d e v a p o t r a n s p i r a t i o n 33 c) S o i l - l i m i t e d e v a p o t r a n s p i r a t i o n .36 d) E s t i m a t i o n o f E v a p o t r a n s p i r a t i o n 37 2. Dry M a t t e r P r o d u c t i o n 38 a) V a r i a t i o n between y e a r s . . .38 b) R e s u l t s o f g r a z i n g s i m u l a t i o n 3 9 c) S p a t i a l v a r i a t i o n and e f f e c t s o f f e r t i l i t y . . . . 42 3. R e l a t i o n s h i p Between Growth and T r a n s p i r a t i o n 44 - v i -a) R e l a t i o n s h i p w i t h e v a p o t r a n s p i r a t i o n 44 b) C o r r e c t i o n f o r bare s o i l e v a p o r a t i o n 46 c) Comparison w i t h o t h e r s t u d i e s 47 E. CONCLUSIONS 48 CHAPTER I I I . A SIMPLE MODEL FOR FORAGE GROWTH IN THE PEACE RIVER REGION 49 A. INTRODUCTION . 49 B. THEORETICAL BASIS OF THE MODEL . . . 51 1. E s t i m a t i n g T r a n s p i r a t i o n . . . . 51 2. E s t i m a t i n g Net R a d i a t i o n . . . . 54 3. S o i l Water B a l a n c e 56 4. R e l a t i o n s h i p Between Growth and T r a n s p i r a t i o n 59 C. EXPERIMENTAL SITE AND MEASUREMENTS. . 61 D. RESULTS AND DISCUSSION 62 1. E s t i m a t i n g Net R a d i a t i o n 62 2. Root Zone Water B a l a n c e 67 a) S e a s o n a l r o o t zone s t o r a g e e s t i m a t e s 67 b) E s t i m a t i n g e v a p o t r a n s p i r a t i o n and t r a n s p i r a t i o n 73 3. E s t i m a t i n g Growth From E v a p o t r a n s p i r a t i o n 74 E. CONCLUSIONS 77 CHAPTER IV. SUMMARY AND CONCLUSIONS 79 REFERENCES 8 4 - v i i -APPENDICES 1 D a i l y Energy B a l a n c e Components f o r 1978 and 1979 90 2 L i s t i n g o f Growth-Water B a l a n c e Program 96 3 Output o f Growth-Water B a l a n c e Program 99 4 Measured and M o d e l l e d Net R a d i a t i o n Data f o r 1978 and 1979. . . 103 5 Forage p r o d u c t i o n a t Sunset P r a i r i e i n 1977, 1978 and 1979 . . . . ' V" - v i i i -LIST OF TABLES Table Page CHAPTER I I . 1 V a r i a t i o n of s o i l b u l k d e n s i t y w i t h depth a t Sunset P r a i r i e f o r Codesa s o i l 20 2 S o i l water r e t e n t i o n c h a r a c t e r i s t i c s f o r Codesa s o i l a t Sunset P r a i r i e ,. .. . . .20 CHAPTER I I I . 1 Comparison of standard e r r o r s of net r a d i a t i o n e s t i m a t e s u s i n g the Idso-Jackson formula, and a r e g r e s s i o n e q u a t i o n 64 2 Rootzone s t o r a g e d a t a f o r 1978 and 1979. (values i n mm are the mean of 4 or 5 r e p l i c a t e s ) 71 - i x -LIST OF FIGURES Pag O u t l i n e map o f B r i t i s h Columbia w i t h i n s e t showing Peace R i v e r r e g i o n and l o c a t i o n o f Sunset P r a i r i e P a s t u r e (From D a v i s , 1978) 2 E x p e r i m e n t a l a r e a a t Sunset P r a i r i e showing l o c a t i o n s o f seven 0.1 ha s i t e s . Shaded a r e a s a r e t r e e d w i t h 5 t o 10 m h i g h deciduous t r e e s 19 Energy b a l a n c e components f o r J u l y 3, 1978 under c o n d i t i o n s o f ample s o i l m o i s t u r e . Daytime Bowen r a t i o i s 0.16 31 Energy b a l a n c e components f o r J u l y 25, 1978 under s o i l - l i m i t e d c o n d i t i o n s . Daytime Bowen r a t i o i s 1.05 32 Daytime e v a p o t r a n s p i r a t i o n f o r 19 7 8 and 1979 v e r s u s r o o t z o n e s t o r a g e . H o r i z o n t a l l i n e s r e p r e s e n t v a l u e s o f E w i t h a - 1.26. Data p o i n t s a r e s t r a t i f i e d by ranges o f E . S o i l l i m i t e d l i n e , E = b0 , u t f l s b = 27 mmd - 1. . S . . . e 34 Measured E v e r s u s E f o r 1978 and 1979 d a t a showing r l c f r e s s i o n and 1:1 l i n e s 35 Accumulated hay growth a t s i t e 1 f o r 1977, 1978 and 1979 growing seasons . . . .38 Comparison o f accumulated growth o f uncut (hay) and c u t ( s i m u l a t e d p a s t u r e ) f o r a g e . V a l u e s a r e averages o f measurements a t s i t e s 1 and 7 w i t h range b a r s shown 4 0 - x -8 Comparison o f accumulated growth o f f e r t i l i z e d and u n f e r t i l i z e d c u t ( s i m u l a t e d p a s t u r e ) f o r a g e . Measurements* a r e t h e average o f t h r e e r e p l i c a t e s a t s i t e s 4 and 6. Shaded a r e a shows range o f accumulated growth o f c u t , u n f e r t i l i z e d f o r a g e growth a t s i t e s 2 t o 6 43 9 Accumulated hay growth v e r s u s accumulated E f o r 1977 and 1979, showing s t a r t i n g d a t e s f o r summation o f E. L i n e showing May 1 s t a r t i n g d a t e assumes average E o f 3 mm d - i from May 1 t o June 7 45 CHAPTER I I I P r o f i l e s o f v o l u m e t r i c s o i l m o i s t u r e w i t h d epth a t s i t e 1 d u r i n g the 1978 growing season 58 C a l c u l a t e d v e r s u s measured Q* u s i n g T measured o n - s i t e and measured o n - s i t e (SP) and a t F o r t S t . John ( F S J ) . . 65 M o d e l l e d r o o t z o n e water s t o r a g e compared w i t h measured v a l u e s i n 1978. . . 68 M o d e l l e d r o o t z o n e water s t o r a g e compared w i t h measured v a l u e s i n 1979. E f f e c t s o f u s i n g measured and m o d e l l e d Q*, and two v a l u e s o f maximum water s t o r a g e (W ) a r e shown 6 9 ^ max S p a t i a l v a r i a t i o n i n measured and m o d e l l e d r o o t z o n e water s t o r a g e i n 1979. The upper, m i d d l e , and lower l i n e s r e p r e s e n t model runs u s i n g i n i t i a l v a l u e s on June 1 from s i t e s 7, 2, and 4 r e s p e c t i v e l y 72 M o d e l l e d accumulated growth compared w i t h measured v a l u e s a t s i t e 1. Growth/ t r a n s p i r a t i o n r a t i o s used i n c a l c u l a t i n g u n c u t (hay) and c u t ( s i m u l a t e d p a s t u r e ) growth were 0.026 and 0.013 t ha -1mm - 1 r e s p e c t i v e l y 75 - x i -E eq LIST OF SYMBOLS a,b,c E m p i r i c a l c o e f f i c i e n t s B Jury-Tanner s o i l e v a p o r a t i o n c o e f f i c i e n t (Chapter II equation 8) c S p e c i f i c heat o f a i r ir D Drainage r a t e e Vapour pr e s s u r e a e* S a t u r a t e d vapour pressure E E v a p o t r a n s p i r a t i o n r a t e E q u i l i b r i u m e v a p o t r a n s p i r a t i o n r a t e E m a x Energy l i m i t e d e v a p o t r a n s p i r a t i o n r a t e E Q E v a p o r a t i o n r a t e from f r e e water surface; S o i l l i m i t e d e v a p o t r a n s p i r a t i o n r a t e E . n E v a p o r a t i o n r a t e from: b a r e " s o i l s o i l c ' E^ T r a n s p i r a t i o n r a t e G Forage growth (above ground dry matter) I I n t e r c e p t i o n ( d a i l y ) K+, Incoming and outgoing shortwave r a d i a t i o n f l u x d e n s i t y , r e s p e c t i v e l y K4- , Incoming shortwave r a d i a t i o n f l u x d e n s i t y c l e a r % ^ 1 on c l o u d l e s s day L L a t e n t heat o f v a p o u r i z a t i o n of water L+, L+ Incoming and outgoing longwave r a d i a t i o n LAI Leaf area index m G r o w t h / t r a n s p i r a t i o n r a t i o N Days from s t a r t of growing season P P r e c i p i t a t i o n r a t e E S - x i i -Net r a d i a t i o n f l u x d e n s i t y Net r a d i a t i o n f l u x d e n s i t y a t s o i l s u r f a c L a t e n t heat f l u x d e n s i t y S o i l h e a t f l u x d e n s i t y S e n s i b l e h e a t f l u x d e n s i t y A l b edo (shortwave r e f l e c t i v i t y ) Canopy r e s i s t a n c e Aerodynamic r e s i s t a n c e Runoff r a t e S l o p e o f s a t u r a t i o n vapour p r e s s u r e v s t e m p e r a t u r e c u r v e Time Mean s c r e e n - h e i g h t a i r t e m p e r a t u r e Dry and w e t - b u l b t e m p e r a t u r e d i f f e r e n c e o v e r v e r t i c a l d i s t a n c e above c r o p canopy Rootzone w a t e r s t o r a g e V a l u e o f W a t wh i c h t r a n s p i r a t i o n i s a p p r o x i m a t e l y z e r o S a t u r a t e d c a p a c i t y o f r o o t z o n e T h i c k n e s s o f s o i l l a y e r P r i e s t l e y - T a y l o r c o e f f i c i e n t P r i e s t l e y - T a y l o r c o e f f i c i e n t f o r bare s o i Bowen r a t i o P s y c h r o m e t r i c c o n s t a n t A t m o s p h e r i c and s u r f a c e e m i s s i v i t i e s S t e f a n - B o l t z m a n c o n s t a n t S o i l b u l k d e n s i t y G r a v i m e t r i c (dry w e i g h t b a s i s ) and v o l u m e t r i c s o i l w a t e r c o n t e n t E x t r a c t a b l e r o o t zone w a t e r c o n t e n t - x i i i -ACKNOWLEDGEMENTS T h i s r e s e a r c h was s u p p o r t e d by a c o n t r a c t from the Land Resource Research I n s t i t u t e o f " A g r i c u l t u r e Canada, and a g r a n t from the B r i t i s h Columbia M i n i s t r y o f A g r i c u l t u r e , f o l l o w i n g recommendations by the B.C. S o i l S c i e n c e Lead Committee. Mr. Bruce Macdonald o f A g r i c u l t u r e Canada has been i n s t r u m e n t a l i n a r r a n g i n g supplementary f u n d i n g f o r the stu d y . C o n s i d e r a b l e a s s i s t a n c e and m a t e r i a l s u p p o r t were p r o v i d e d by the A i r S t u d i e s B ranch, B.C. M i n i s t r y o f E n v i r o n -ment, thanks t o Dr. R i c k W i l s o n , who i n i t i a t e d t h e s t u d y , and to Mr. Rod D a v i s , who was e x t r e m e l y c o o p e r a t i v e i n making a v a i l a b l e d a t a c o l l e c t e d d u r i n g h i s t h e s i s r e s e a r c h a t Sunset P r a i r i e i n 19 77. Mr. P e t e r M o u n t f o r d a s s i s t e d g r e a t l y by h a n d - c o m p i l i n g d a t a which would o t h e r w i s e have been c o n s i d e r -a b l y d e l a y e d . R e g i o n a l c l i m a t e d a t a used i n the t h e s i s was c o l l e c t e d and a n a l y z e d by the A i r S t u d i e s Branch. The Sunset P r a i r i e P a s t u r e Research Committee was e x t r e m e l y c o o p e r a t i v e i n a r r a n g i n g f e n c i n g o f the r e s e a r c h e x c l o s u r e s , and i n making a t r a i l e r a v a i l a b l e f o r accommodation i n 1979 and 19 80. I would l i k e t o thank M s s r s . J a c k Dobb and Ross Green, B.C. M i n i s t r y o f A g r i c u l t u r e , Mr. John Farrow, N o r t h e r n L i g h t s Community C o l l e g e , and Mr. B i l l B a i l e y , A g r i c u l t u r e Canada Research S t a t i o n , B e a v e r l o d g e , A l b e r t a , f o r t h e i r s u p p o r t and f o r p r o v i d i n g sample d r y i n g f a c i l i t i e s . - x i v -Dr. Andy B l a c k has been the s c i e n t i f i c a u t h o r i t y f o r the p r o j e c t s i n c e September, 1978, and as my a d v i s o r s i n c e t h a t time has o f f e r e d me i n v a l u a b l e g u i d a n c e . Dr. Tim Oke, Department o f Geography, has a l s o p r o v i d e d c o n s i d e r a b l e a d v i c e . M s s r s . Owen Hertzman, Bob S t a t h e r s , and Dave S p i t t l e h o u s e c o n t r i b u t e d g r e a t l y t o t h i s t h e s i s n o t o n l y by t h e i r t e c h n i c a l c o n t r i b u t i o n s , b u t more i m p o r t a n t l y t h r o u g h t h e i r d i s c u s s i o n and comments. M s s r s . P a t Wong and Ra l p h Adams worked e x t r e m e l y h a r d t o complete r e p a i r s and m o d i f i c -a t i o n s o f the e l e c t r o n i c equipment b o t h b e f o r e and d u r i n g the f i e l d season. I would l i k e t o thank the K i r t z i n g e r f a m i l y o f Sunset P r a i r i e f o r making us f e e l welcome i n t h e i r home and i n the community; a l l o f us who worked on the p r o j e c t e n j o y e d t h e i r f e l l o w s h i p and gained' a b e t t e r p e r c e p t i o n o f a g r i c u l t u r e i n the a r e a through our a s s o c i a t i o n . F i n a l l y , I would l i k e t o thank the members o f my f a m i l y and my f r i e n d s , e s p e c i a l l y Jane Watson, f o r t h e i r c o n t i n u a l s u p p o r t and l o v e . - 1 -CHAPTER I . INTRODUCTION Large t r a c t s o f l a n d i n t h e Peace R i v e r r e g i o n a re b e i n g c o n s i d e r e d f o r p o t e n t i a l a g r i c u l t u r a l use, but t h e r e a r e l i m i t a t i o n s t o t h e i r development. I n a d d i t i o n t o the economic problems o f l o c a t i o n , t h e r e a re c l i m a t i c l i m i t a t i o n s t o c r o p growth. R e g i o n a l l a n d - e v a l u a t i o n t e c h n i q u e s such as t h a t demonstrated by W i l l i a m s e t a l . (1980) r e q u i r e v e r i f i c a t i o n , p r e f e r a b l y i n c l u d i n g l o c a l l y d e r i v e d y i e l d -c l i m a t e r e l a t i o n s h i p s . I n o r d e r t o be u s e f u l on t h e s c a l e 2 o f t h e r e g i o n (18,000 km ) t h e r e l a t i o n s h i p s s h o u l d be based on e a s i l y o b t a i n a b l e d a t a . Many models have been d e v e l o p e d t o r e l a t e p l a n t y i e l d t o c l i m a t i c f a c t o r s . R e c e n t l y , models have been o r i e n t e d towards e x t r e m e l y s h o r t time s c a l e s , o f t h e o r d e r o f s i n g l e h y d r o l o g i c e v e n t s , o r p l a n t p h y s i o l o g i c a l p r o c e s s e s . T h i s l e v e l o f d e t a i l i s u s e f u l i n r e s e a r c h a p p l i c a t i o n s , but f o r r e g i o n a l s t u d i e s s i m p l e r models a r e r e q u i r e d . In 19 77, t h e B.C. M i n i s t r y o f Environment began a p r o j e c t t o s t u d y t h e r e l a t i o n s h i p between p a s t u r e p r o d u c t i v i t y and c l i m a t e i n t h e Peace R i v e r r e g i o n . A st u d y s i t e was e s t a b l i s h e d i n t h e Sunset P r a i r i e Community P a s t u r e , near F o r t S t . John, B.C. ( F i g u r e 1 ) . D u r i n g the f i r s t y e a r o f the s t u d y , m i c r o m e t e o r o l o g i c a l i n s t r u m e n t a t i o n was o p e r a t e d - 2 -F i g u r e 1. O u t l i n e map o f B r i t i s h Columbia w i t h i n s e t showing Peace R i v e r r e g i o n and l o c a t i o n o f Sunset P r a i r i e P a s t u r e (From D a v i s , 1978) . - 3 -d u r i n g t h e g r owing season, and p l a n t p r o d u c t i o n was measured. The s t u d y c o n t i n u e d i n 1978, w i t h i n t e r m i t t e n t m i c r o m e t e o r o l o g i c a l measurements s u p p l e m e n t i n g b a s i c c l i m a t e and p r o d u c t i v i t y d a t a . I n 19 79, t h e s t u d y was extended t o s i x a u x i l i a r y s i t e s i n o r d e r t o a s s e s s v a r i a t i o n s w i t h i n t h e p a s t u r e . D u r i n g 19 80 i n v e s t i g a t i o n s were c o n t i n u e d a t two o t h e r community p a s t u r e s t o t e s t t h e r e l a t i o n s h i p s found a t Sunset P r a i r i e . T h i s t h e s i s c o n s t i t u t e s a p o r t i o n o f t h e r e s e a r c h c a r r i e d o u t under A g r i c u l t u r e Canada c o n t r a c t #OSU 78-00211, and seeks t o a d d ress t h e f o l l o w i n g o b j e c t i v e s : 1. To d e t e r m i n e whether r e l a t i o n s h i p s e x i s t between p a s t u r e p r o d u c t i v i t y and evapo-t r a n s p i r a t i o n under v a r i o u s growing c o n d i t i o n s . 2. To d e t e r m i n e whether t h e s e r e l a t i o n s h i p s can be used t o d e v e l o p a model o f p a s t u r e p r o d u c t i o n t h a t r e q u i r e s d a t a o b t a i n a b l e by l a n d managers. 3. To t e s t t h e r e l a t i o n s h i p s and the model f o r a v a r i e t y o f c o n d i t i o n s and l o c a t i o n s . The f i r s t o b j e c t i v e i s a d d r e s s e d i n C h apter I I , where a l i n e a r r e l a t i o n s h i p between.above-ground dry m a t t e r p r o d u c t i o n and t r a n s p i r a t i o n i s p r e s e n t e d , based on d a t a f o r two y e a r s when t h e r e was ample s o i l m o i s t u r e . The r e l a t i o n s h i p f o r a s i m u l a t e d monthly g r a z i n g r o t a t i o n i s compared w i t h t h a t f o r hay growth. The s e n s i t i v i t y o f t h e r e l a t i o n s h i p t o f e r t i l i t y i s a l s o examined. - 4 -The second, and t h i r d o b j e c t i v e s a r e a d d r e s s e d i n C h apter I I I , i n w h i c h a model i s p r e s e n t e d f o r e s t i m a t i n g p a s t u r e p r o d u c t i o n u s i n g r o u t i n e l y a v a i l a b l e d a t a . The model c o n s i s t s o f a g r o w t h / t r a n s p i r a t i o n r e l a t i o n s h i p , and a s i m p l e r o o t z o n e w a t e r budget w h i c h i s used t o account f o r s o i l m o i s t u r e l i m i t a t i o n s . - 5 -CHAPTER I I . TRANSPIRATION AND GROWTH RELATIONSHIPS AT SUNSET PRAIRIE PASTURE A. INTRODUCTION In t h e Peace R i v e r r e g i o n o f B r i t i s h Columbia and A l b e r t a , c r o p y i e l d s a r e s u s c e p t i b l e t o b o t h m o i s t u r e and t e m p e r a t u r e l i m i t a t i o n s ( W i l l i a m s e t a l . , 1980). G r a i n cannot be grown t o m a t u r i t y i n much o f the r e g i o n , so hay and p a s t u r e p r o d u c t i o n a r e e x t e n s i v e . New l a n d i s b e i n g b r o u g h t i n t o p r o d u c t i o n , and assessment o f i t s p o t e n t i a l i s needed t o h e l p r e g i o n a l p l a n n e r s and managers. Crop p r o d u c t i v i t y models d e v e l o p e d i n more s o u t h e r l y l o c a t i o n s o f t e n r e q u i r e d a t a w h i c h are not a v a i l a b l e i n n o r t h e r n a g r i c u l t u r a l a r e a s , so s i m p l e r p r o c e d u r e s are d e s i r a b l e . Much of t h e v a r i a t i o n o f c r o p y i e l d i n t h e Canadian P r a i r i e s i s due t o weather ( W i l l i a m s , 1970). W i l l i a m s found r e g i o n s where a f a c t o r , such a s . r a i n f a l l , was p o s i t i v e l y c o r r e l a t e d w i t h y i e l d i n dry y e a r s , and n e g a t i v e l y c o r r e l a t e d i n wet y e a r s . T h i s c o u l d o c c u r i f y i e l d was w a t e r l i m i t e d i n d r y y e a r s , and energy l i m i t e d i n wet y e a r s . The Peace R i v e r r e g i o n i s such a r e g i o n , i n w h i c h a p p l i c a t i o n o f s i m p l e s t a t i s t i c a l t e c h n i q u e s t o y i e l d p r e d i c t i o n i s u n l i k e l y t o be s u c c e s s f u l . S t a t i s t i c a l t e c h n i q u e s are g e n e r a l l y most u s e f u l i n p r e d i c t i n g f i n a l y i e l d s , b u t because t h e y do not o f t e n r e l y - 6 -on understanding growth processes, they are not g e n e r a l l y used t o p r e d i c t the course of y i e l d through the growing season. Models which are developed to simulate crop growth f r e q u e n t l y i n c o r p o r a t e water l i m i t a t i o n s , but may not emphasize temperature or energy l i m i t a t i o n s . S e l i r i o and Brown (1979), i n t h e i r model of forage y i e l d , r e l a t e growth to growing degree days, and apply water l i m i t a t i o n as a r e d u c t i o n f a c t o r . T h e i r approach i s q u i t e s u c c e s s f u l , but i t r e p r e s e n t s the i n t e g r a t i o n o f many years of r e s e a r c h i n Ont a r i o , much of which has not been done i n the Peace R i v e r r e g i o n . I t i s p r a c t i c a l t o t r y to r e l a t e growth to a s i n g l e v a r i a b l e which d e s c r i b e s both water and energy l i m i t a t i o n s . E v a p o t r a n s p i r a t i o n depends on the a v a i l a b i l i t y of water and energy to the crop, and has been used w i t h c o n s i d e r a b l e success as a y i e l d p r e d i c t o r (Briggs and Shantz, 1913; S t a p l e and Lehane, 1954; DeWit, 1958; A r k l e y , 1963; Rose e t a l . , 1972; Hanks, 1974; van Keulen, 1975). DeWit (1958) d i s c u s s e d the concept o f an average growing season r e l a t i o n s h i p between p l a n t growth and t r a n s p i r a t i o n expressed as: G = m / E f cdt (1) where G i s the above'-qround dry matter growth, E^ i s the t r a n s p i r a t i o n r a t e , dt i s a time increment, and m i s the g r o w t h / t r a n s p i r a t i o n r a t i o f o r the growing season. In - 7 -p r e d i c t i n g g r a i n y i e l d s i t has been r e c o g n i z e d t h a t s u s c e p t i b i l i t y t o w a t e r l i m i t a t i o n v a r i e s w i t h the s t a g e o f p l a n t m a t u r i t y ( B i s c o e e t a l . , 1975; Morgan e t al^. , 1980), and t h e c o n c e p t o f a s i n g l e t r a n s p i r a t i o n r a t i o has been m o d i f i e d t o a l l o w f o r w e i g h t i n g o f c r i t i c a l p e r i o d s (Hanks and A s h c r o f t , 1977). M o d e l l i n g hay p r o d u c t i v i t y i s s i m p l e r , s i n c e v e g e t a t i v e growth i s not so s u b j e c t t o c r i t i c a l p e r i o d s as g r a i n y i e l d . S e v e r a l workers have s u c c e s s f u l l y " r e l a t e d p a s t u r e growth t o e v a p o t r a n s p i r a t i o n under c o n d i t i o n s o f ample m o i s t u r e s u p p l y ( S t a n h i l l , 1960; Penman, 1962; Rose e t a l . , 1972; D a v i s , 1978). Rose e t a l . (1972) show how f e r t i l i z e r l e v e l a f f e c t s t h i s r e l a t i o n s h i p f o r T o w n s v i l l e S t y l o i n A u s t r a l i a and i n c o r p o r a t e t h i s i n a s i m p l e model. I t i s a l s o known t h a t p e r i o d i c c u t t i n g o r g r a z i n g can reduce growth (Brougham, 19 56; Younger and Nudge, 19 76; Johns and Lazenby, 1973). The o b j e c t i v e s o f t h i s c h a p t e r a r e ( i ) t o determine the r e l a t i o n s h i p between c r o p growth and d u r i n g two growing sea s o n s , 1977 and 1979, when growth was not l i m i t e d by s o i l m o i s t u r e , ( i i ) t o f i n d t h e dependence o f the r e l a t i o n s h i p on f e r t i l i t y , and ( i i i ) t o compare y i e l d s o f uncut f o r a g e (hay growth) w i t h y i e l d s o f f o r a g e s u b j e c t e d t o p e r i o d i c c u t t i n g ( s i m u l a t e d g r a z i n g ) . - 8 -B. BACKGROUND 1. C a l c u l a t i n g E v a p o t r a n s p i r a t i o n The e v a p o t r a n s p i r a t i o n r a t e (E) o f a c r o p i s g i v e n by t h e Penman-Monteith e q u a t i o n as f o l l o w s ( M o n t e i t h , 1965): [ s / ( s + Y ) ] [(Q*-Q r)+Pc .[e*(T ) - e J / ( s + T ) r ] (1+[Y / ( s + Y ) ] r / r )L u ; c a where s i s t h e s l o p e o f t h e s a t u r a t i o n vapour p r e s s u r e c u r v e , Y i s t h e p s y c h r o m e t r i c c o n s t a n t , Q* i s t h e n e t r a d i a t i o n f l u x d e n s i t y , Qn i s t h e s o i l heat f l u x d e n s i t y , P i s t h e d e n s i t y o f a i r , c i s t h e s p e c i f i c heat o f a i r , e*(T ) i s t h e P a s a t u r a t i o n vapour p r e s s u r e a t a i r t e m p e r a t u r e , e i s the a vapour p r e s s u r e o f t h e a i r , r i s t h e aerodynamic r e s i s t a n c e , r c i s t h e canopy r e s i s t a n c e , and L i s t h e l a t e n t heat o f v a p o u r i z a t i o n . S i n c e e v a l u a t i o n o f r and r on a r o u t i n e b a s i s i s c a d i f f i c u l t , e v a p o t r a n s p i r a t i o n w i l l be c a l c u l a t e d as d e s c r i b e d i n t h e f o l l o w i n g s e c t i o n s . a) E n e r g y - l i m i t e d e v a p o t r a n s p i r a t i o n (E ) £ E max P r i e s t l e y and T a y l o r (1972) found t h a t f o r e x t e n s i v e wet s u r f a c e s and v e g e t a t e d s u r f a c e s w e l l - s u p p l i e d w i t h w a t e r , the e v a p o r a t i o n r a t e under t h e s e c o n d i t i o n s (E ) c o u l d be ^ max - 9 -r e l a t e d t o t h e f i r s t term o f (2) as f o l l o w s : E max - a (S/(S+Y)) (Q*-Q Q)/L (3) where a i s an e x p e r i m e n t a l l y d e t e r m i n e d c o e f f i c i e n t , and th e r e m ainder o f t h e r i g h t - h a n d s i d e i s r e f e r r e d t o as the e q u i l i b r i u m e v a p o r a t i o n r a t e ( S l a t y e r and M c l l r o y , 1961). P r i e s t l e y and T a y l o r (1972) found t h a t a was 1.28 on a 24-hour b a s i s f o r d a t a s e t s from s e v e r a l p a r t s o f t h e w o r l d . Many s t u d i e s have s i n c e r e p o r t e d 24-hour a v a l u e s o f 1.25 +0.05 (Tanner and J u r y , 1976; S t e w a r t and Rouse, 1977; DeB r u i n and Keij m a n , 1979; Mukammal and Neuman, 1977). D a v i s (19 78) r e p o r t e d a daytime v a l u e o f 1.2 8 f o r Sunset P r a i r i e i n 1977. Tanner and J u r y (1976) showed t h a t a v a l u e s c a l c u l a t e d on a daytime b a s i s a r e s m a l l e r t h a n t h o s e c a l c u l a t e d on. a 24-hour b a s i s , s i n c e Q*-Q_, i s s m a l l e r f o r 24 hours t h a n f o r t h e daytime p e r i o d . McNaughton e t a l . (1979) suggested t h a t t h e l i m i t s o f <a i n an environment f r e e o f l o c a l a d v e c t i o n a r e : The l o w e r l i m i t c o r r e s p o n d s t o e v a p o r a t i o n a t t h e e q u i l i b r i u m r a t e , w h i l e the upper l i m i t i m p l i e s t h a t a l l a v a i l a b l e energy (Q*-Q_) i s used f o r e v a p o r a t i o n . C l e a r l y , 1 < or.. < (s+ y )/s (4) - 10 -e v a p o r a t i o n a t the h i g h e r r a t e cannot be s u s t a i n e d , s i n c e atmospheric c o n v e c t i o n would cease i n the absence of a s e n s i b l e heat f l u x . The upper bound i n (4) ranges from 1.18 a t 40°C to 2.46 a t 0°C. S e v e r a l s t u d i e s have suggested t h a t there may be a seasonal t r e n d i n values of a , and have r e p o r t e d h i g h e r v a l u e s i n months wit h lower temperatures 5 (deBruin and Keijman, 1979; Jackson e t ^ a l . , 1975). For most s t u d i e s , however, the value seems to be n e a r l y constant throughout the growing season. The P r i e s t l e y and T a y l o r method has drawn c r i t i c i s m on t h e o r e t i c a l grounds (McNaughton, 1976; Monteith, 1978; Shuttleworth and C a l d e r , 1979) but there seems to be c o n s i d e r a b l e evidence of i t s u s e f u l n e s s . b) S o i l - l i m i t e d e v a p o t r a n s p i r a t i o n (E ) - = s Under c o n d i t i o n s of low s o i l moisture, t r a n s p i r a t i o n becomes l i m i t e d by the a b i l i t y of the s o i l t o supply moisture to the p l a n t . P r i e s t l e y and T a y l o r (1972) r e f e r to t h i s as the d r y i n g phase, and show E / E ^ as a l i n e a r f u n c t i o n of the r o o t zone water storage (W) . R i t c h i e (1972) p l o t t e d E/-E as a f u n c t i o n of the f r a c t i o n of e x t r a c t a b l e water i n the root.^zone (0 ), d e f i n e d as f o l l o w s : e e = (w - w . j / w a v - w . ) (5) e mm max min - 11 -where E i s t h e f r e e w a t e r e v a p o r a t i o n r a t e , W i s o ^ ' max t h e r o o t zone s t o r a g e a t s a t u r a t i o n , and W . i s the v a l u e 3 m i n o f r o o t zone s t o r a g e a t w h i c h t r a n s p i r a t i o n v i r t u a l l y c e a s e s . Tanner and R i t c h i e (1974) a n a l y z e d 15 e x p e r i m e n t s and showed t h a t such a r e l a t i o n s h i p was a r e a s o n a b l e d e s c r i p t i o n o f t h e r e s u l t s . B l a c k (1979) showed t h a t evapo-t r a n s p i r a t i o n a t two d i f f e r e n t f o r e s t s i t e s w i t h s i m i l a r s o i l s c o u l d be d e s c r i b e d u s i n g t h e same f u n c t i o n o f e x t r a c t a b l e r o o t zone water . Based on comments by McNaughton 9 e t a l . (1979), B l a c k and S p i t t l e h o u s e (1981) used E = b 9 (6) s e where b i s an e x p e r i m e n t a l l y d e t e r m i n e d c o e f f i c i e n t . 2. E s t i m a t i n g T r a n s p i r a t i o n (E^.) B e f o r e t h e p l a n t canopy i s f u l l y d e v e l o p e d , e v a p o r a t i o n from t h e s o i l r e p r e s e n t s a s i g n i f i c a n t f r a c t i o n of e v a p o t r a n s p i r a t i o n . S i n c e t h e e v a p o r a t i v e f l u x i s not a s s o c i a t e d w i t h growth, i t i s d e s i r a b l e t o f i n d a method of s e p a r a t i n g e v a p o r a t i o n and t r a n s p i r a t i o n . S e v e r a l methods based on t h e l e a f a r e a i n d e x ( L A I ) , o f t h e c r o p have been proposed ( R i t c h i e , 1972; Tanner and J u r y , 1976). - 12 -Tanner and J u r y s u g g e s t e d t h a t t h e two components c o u l d be e x p r e s s e d i n terms o f t h e p r o p o r t i o n o f n e t r a d i a t i o n i n c i d e n t on s o i l and l e a v e s as f o l l o w s : E s o i l = « S ( S / ( S + Y ) ) ( Q * G - Q G ) ( 7 A ) E v = a (s/(s+ Y )) (Q*-Qr) (7b) m a x \j where E ., i s t h e e v a p o r a t i o n r a t e from bare s o i l , a i s s o i l ^ ' s the P r i e s t l e y - T a y l o r c o e f f i c i e n t f o r s o i l , and Q* i s t h e Or n e t r a d i a t i o n f l u x d e n s i t y a t t h e s o i l s u r f a c e . T r a n s p i r a t i o n i s c a l c u l a t e d as t h e d i f f e r e n c e between (7a) and (7b). Tanner and J u r y s t a t e d t h a t ot was i n i t i a l l y t h e same as t h a t f o r t h e c r o p canopy, and t h a t i t g r a d u a l l y approached u n i t y as t h e canopy approached complete c o v e r . They a l s o p r e s e n t e d r e l a t i o n s h i p s l i n k i n g LAI t o s t a n d i n g dry m a t t e r (G), and p e r c e n t c o v e r . T h e i r r e l a t i o n s h i p f o r c a l c u l a t i n g E ., i s : ^ s o i l E ., = E [ e x p ( - B - L A I ) ] (8) s o i l max ^ where B i s an e m p i r i c a l c o n s t a n t . T h e i r r e l a t i o n s h i p LAI = 0.02 (% c o ver) i s c o n s i s t e n t w i t h Johns and Lazenby (1973), who r e p o r t e d t h a t f u l l c o v e r c o r r e s p o n d e d t o LAI•>_ 2 f o r p a s t u r e . I n t h i s c h a p t e r a r e l a t i o n s h i p based on s t a n d i n g d r y m a t t e r i s p r e s e n t e d . - 13 -3. R e l a t i o n s h i p Between Growth and E v a p o t r a n s p i r a t i o n a) P h y s i o l o g i c a l b a s i s f o r t h e r e l a t i o n s h i p The r e l a t i o n s h i p between t r a n s p i r a t i o n and d r y m a t t e r p r o d u c t i o n i s i n d i r e c t , s i n c e t h e water l o s t by t r a n s p i r a t i o n i s n o t a p h o t o s y n t h e t i c p r o d u c t . The most d i r e c t measure o f n e t a s s i m i l a t i o n i s n e t carbon d i o x i d e (CC^) u p t a k e . CC^ and water vapour f l u x e s s h a r e a common pathway, v i a the stomata, w h i c h c o n t r o l t h e r a t e o f d i f f u s i o n o f t h e s e gases. S i n c e t h e d i f f u s i o n c o e f f i c i e n t s o f t h e two e n t i t i e s are s i m i l a r , t h e r a t i o o f t h e two f l u x e s i s c l o s e l y r e l a t e d t o the r a t i o o f t h e i r c o n c e n t r a t i o n g r a d i e n t s a c r o s s t h e s t o m a t a l p o r e s . S p e c i e s d i f f e r e n c e s i n m e s o p h y l l r e s i s t a n c e t o CC^ w o u l d a f f e c t t h e v a l u e o f t h e r a t i o ( M o n t e i t h , 19 6 6 ) . S i n c e t h e r a t i o o f t h e c o n c e n t r a t i o n d i f f e r e n c e s w i l l change w i t h a t m o s p h e r i c h u m i d i t y , t h e g r o w t h / t r a n s p i r a t i o n r a t i o s h o u l d a l s o change ( B i e r h u i z e n and S l a t y e r , 1965). The p h o t o s y n t h e t i c p r o c e s s becomes l i g h t s a t u r a t e d , b u t t r a n s p i r a t i o n r a t e s have been o b s e r v e d t o i n c r e a s e almost l i n e a r l y w i t h s o l a r i r r a d i a n c e , i f w a ter i s a d e q u a t e l y s u p p l i e d ( M o n t e i t h , 1966). I t i s t h e r e f o r e l i k e l y t h a t t h e g r o w t h / t r a n s p i r a t i o n r a t i o w i l l be h i g h e r under c o n d i t i o n s o f low i r r a d i a n c e . I f t h e s e hypotheses a r e c o r r e c t , c a r e must be e x e r c i s e d i n comparing g r o w t h / t r a n s p i r a t i o n r a t i o s d e r i v e d under d i f f e r i n g l e v e l s o f i r r a d i a n c e o r a t m o s p h e r i c h u m i d i t y . - 14 -I t s h o u l d a l s o be c o n s i d e r e d t h a t t r a n s p i r a t i o n o f t e n ceases a t n i g h t , w h i l e r e s p i r a t i o n c o n t i n u e s ; however, n i g h t - t i m e r e s p i r a t i o n a c t i v i t y appears t o be p o s i t i v e l y c o r r e l a t e d w i t h daytime p h o t o s y n t h e t i c a c t i v i t y ( B i s c o e e t a l . , 1975; Rosenberg e t a l . , 1974). A n o c t u r n a l t e m p e r a t u r e t h a t i s 10°C lower than daytime t e m p e r a t u r e r e s u l t s i n a r e s p i r a t i o n r a t e about h a l f t h a t i n t h e daytime ( B i s c o e e t a l . , 1975). The r e l a t i v e l y s m a l l magnitude of n i g h t - t i m e r e s p i r a t i o n l o s s e s , and t h e i r c o r r e l a t i o n w i t h daytime > a c t i v i t y w i l l h e l p t o p r e s e r v e th e r e l a t i o n s h i p between t r a n s p i r a t i o n and c r o p growth, e s p e c i a l l y f o r s h o r t c o o l n i g h t s , such as a r e o f t e n e x p e r i e n c e d i n n o r t h e r n r e g i o n s . b) E x p e r i m e n t a l s u p p o r t f o r t h e r e l a t i o n s h i p B r i g g s and Shantz (1913) found t h a t dry m a t t e r p r o d u c t i o n was l i n e a r l y r e l a t e d t o t r a n s p i r a t i o n , and t h a t t h e r a t i o v a r i e d between s p e c i e s . DeWit (1958) c o n f i r m e d t h e s e f i n d i n g s i n f i e l d s t u d i e s , and n o t e d t h a t the growth/ t r a n s p i r a t i o n r a t i o was lower i n more a r i d r e g i o n s . S t a p l e and Lehane (1954) found a n e a r l y l i n e a r r e l a t i o n s h i p f o r wheat y i e l d s i n Saskatchewan, even under, c o n d i t i o n s o f m o i s t u r e l i m i t a t i o n . S t a n h i l l (1960) showed l i n e a r r e l a t i o n -s h i p s f o r w e l l w a t e r e d g r a s s a t seven l o c a t i o n s r a n g i n g from T r i n i d a d t o Denmark, w i t h th e most e f f i c i e n t use o f water - 15 -o c c u r r i n g a t h i g h l a t i t u d e s . M o n t e i t h (1966) c o n f i r m e d t h e s e o b s e r v a t i o n s , s t a t i n g t h a t a g i v e n s p e c i e s i s l i k e l y t o produce more d r y m a t t e r p e r u n i t o f t r a n s p i r a t i o n i n a c l o u d y , humid c l i m a t e t h a n i n a sunny, a r i d c l i m a t e . S e v e r a l methods have been proposed t o ac c o u n t f o r a t m o s p h e r i c h u m i d i t y l e v e l s . DeWit (1958) suggested t h a t a m o d i f i e d t r a n s p i r a t i o n r a t i o be c a l c u l a t e d by d i v i d i n g a s p e c i e s ' d r y m a t t e r p r o d u c t i o n r a t e ( i n kg ha "'"d ^) by t h e f r e e - w a t e r e v a p o r a t i o n r a t e ( E Q , i n mm d "*") . T h i s approach, and t h a t of B i e r h u i z e n and S l a t y e r (1965), i n w h i c h t h e y s u b s t i t u t e d vapour p r e s s u r e d e f i c i t f o r E , h e l p t o account f o r d i f f e r e n t h u m i d i t y l e v e l s , a l t h o u g h van K e u l e n (1975) r e p o r t e d t h a t the l a t t e r method d i d not p r o p e r l y account f o r v a r i a t i o n s between seasons. These methods w i l l n o t account f o r d i f f e r e n c e s between l a t i t u d e s , e x c e p t as t h e l a t t e r a r e r e f l e c t e d i n t h e d a i l y e v a p o r a t i o n r a t e . F o r i n s t a n c e , the d a i l y r a d i a t i o n t o t a l a t 56°N i s t h e same as t h a t a t 4 0°N i n t h e summer (Ca r d e r , 1956), y e t t h e g r o w t h / t r a n s p i r a t i o n r a t i o i s h i g h e r a t t h e more n o r t h e r l y l a t i t u d e , due t o t h e more f a v o u r a b l e d i s t r i b u t i o n o f r a d i a t i o n ( l o n g e r d a y l e n g t h ) and c o o l e r t e m p e r a t u r e s . Van Ke u l e n (1975) d e v e l o p e d a'method f o r c a l c u l a t i n g g r o w t h / t r a n s p i r a t i o n r a t i o s f o r d i f f e r e n t l a t i t u d e s and p r e v a i l i n g c l i m a t e s . H i s t e s t s f o r I s r a e l show p r o m i s i n g r e s u l t s but i t remains t o be shown i f h i s model i s g e n e r a l l y a p p l i c a b l e . - 16 -Most o f t h e l i t e r a t u r e r e p o r t s n o n - l i m i t i n g n u t r i e n t l e v e l s , but Rose e t a l . (1972) proposed t h a t a f a m i l y o f l i n e a r r e l a t i o n s h i p s e x i s t e d f o r d i f f e r e n t f e r t i l i t y l e v e l s . Walker (1978) proposed a n u t r i e n t s t a t u s f a c t o r , w h i c h he s u g g e s t e d would v a r y , depending on i n t e r a c t i o n s between n u t r i e n t s t a t u s and w ater a v a i l a b i l i t y . A l t h o u g h t h e g r o w t h / t r a n s p i r a t i o n r a t i o concept i s u s e f u l i n e s t a b l i s h i n g v a r i a t i o n s between s p e c i e s , c l i m a t e s , and l a t i t u d e s , i t i s n o t y e t p o s s i b l e t o c a l c u l a t e such r a t i o s from b a s i c e n v i r o n m e n t a l and p h y s i o l o g i c a l d a t a . Even so, t h e c o n c e p t p r e s e n t s a u s e f u l b a s i s f o r a c l i m a t i c a l l y based growth i n d e x . By u s i n g a l i n e a r r e l a t i o n s h i p , d a t a can be used f o r p e r i o d s r a n g i n g from days t o weeks. I t i s p o s s i b l e t h a t s t o m a t a l c o n t r o l o f t r a n s p i r a t i o n may h e l p t o p r e s e r v e t h e c o n s t a n c y o f t h e r e l a t i o n s h i p ( M o n t e i t h , 1966), e s p e c i a l l y under w a t e r - l i m i t i n g c o n d i t i o n s ( S t a n h i l l , 1960). Growth c a l c u l a t i o n s o v e r s h o r t time i n t e r v a l s (e.g. 1 hour) s h o u l d be a v o i d e d , s i n c e the c oncept r e p r e s e n t s an average r e l a t i o n s h i p between n o n - l i n e a r , i n t e r a c t i n g p r o c e s s e s . c . EXPERIMENTAL PROCEDURE 1. E x p e r i m e n t a l S i t e The f i e l d measurements were made a t the Sunset P r a i r i e Community P a s t u r e (55°56'N, 120°45'W), a p p r o x i m a t e l y 50 km s o u t h o f F o r t S t . John, B.C. The main s i t e was d e s c r i b e d by D a v i s (1978), and c o n s i s t s o f a 160 m x 40 m e n c l o s u r e a t t h e downwind end o f a 4 5 ha g r a z e d p a s t u r e , a t an e l e v a t i o n o f 800 m. The p a s t u r e was seeded i n 1968 w i t h a m i x t u r e o f t i m o t h y (Phleum p r a t e n s e ) , r e d f e s c u e ( F e s t u c a r u b r a ) , and a l s i k e c l o v e r ( T r i f o l i u m r e p e n s ) , f e r t i l i z e d i n May 1977 and i n May and October 1978 w i t h 100 kg h a - 1 o f 30-0-0 ( N i t r o g e n - P h o s p h o r u s - P o t a s s i u m ) . • The e n c l o s u r e c o n t a i n e d f i e l d i n s t r u m e n t a t i o n , s o i l and p l a n t s a m p l i n g a r e a s , and a t r a i l e r and a 3kW Onan d i e s e l g e n e r a t o r near t h e downwind end. In t h e d i r e c t i o n o f t h e p r e v a i l i n g southwest w i n d , f e t c h was a p p r o x i m a t e l y 500 m, and i n no d i r e c t i o n was the f e t c h l e s s t h a n 250 m. The p a s t u r e i s s i t u a t e d near the margin o f t h e c u l t i v a t e d a g r i c u l t u r a l p o r t i o n o f the r e g i o n and i s p a r t o f a 250 ha a r e a o f tame p a s t u r e on g e n t l y r o l l i n g t e r r a i n , w i t h c l e a r e d f i e l d s t o t h e so u t h and e a s t , and d e c i d u o u s f o r e s t s t o t h e west (mainly a s p e n ) . U n t i l 1977 t h e 45 ha p a s t u r e was a s i n g l e u n i t , b u t s i n c e t h a t time - 18 -i t has been used as a three-paddock r o t a t i o n a l g r a z i n g system, w i t h a 4 ha r e s e r v e . In 1979, s i x a d d i t i o n a l s i t e s were e s t a b l i s h e d , as shown i n F i g u r e 1. Each 0.1 ha s i t e was f e n c e d , and 4 o r 5 n e u t r o n t u b e s were i n s t a l l e d as w e l l as a s t o r a g e r a i n g a u g e , r e c o r d i n g thermograph, and maximum and minimum thermometers, l o c a t e d i n a Stevenson s c r e e n a t 1.5 m. H a l f o f s i t e s 4 and 6 were f e r t i l i z e d i n May 1979 w i t h 100 kg h a " 1 o f 40-20-0, and p l o t s f o r f o r a g e growth s a m p l i n g were e s t a b l i s h e d a t a l l s i t e s . S o i l p r o f i l e d e s c r i p t i o n s were completed a t each s i t e , and t e x t u r a l a n a l y s i s showed a l l s i t e s t o be c l a y loam. S i t e s 2 and 4 were c l a s s i f i e d as A l c a n s e r i e s , and t h e o t h e r s as Codesa, w i t h a s c a t t e r e d p e b b l e l a y e r a t 30 cm b e i n g the d i s t i n g u i s h i n g f e a t u r e (A. Green, P e r s o n a l Communication). Both s o i l s b e l o n g t o t h e Gray L u v i s o l s o i l g r e a t group. S o i l b u l k d e n s i t y (pg) measurements have been made by D a v i s ( u n p u b l i s h e d ) , and d u r i n g the 197 8 s u r v e y o f t h e a u x i l i a r y s i t e s and the 1979 f i e l d season (Hertzman, 1981). The mean v a l u e s have been summarized i n T a b l e 1. L a b o r a t o r y s o i l w a t e r r e t e n t i o n d a t a f o r the main s i t e were c o l l e c t e d by D a v i s ( u n p u b l i s h e d ) and Hertzman e t a l . (1981). D a v i s ' v a l u e s were o b t a i n e d from 2.5 cm d i a m e t e r c o r e s u s i n g c e r a m i c e x t r a c t i o n p l a t e s . The d a t a i n Hertzman et. a l . were o b t a i n e d u s i n g the hanging column method f o r a s l a b 15x30x5 cm. Hertzman e t a l . r e p o r t good agreement between t h e d a t a from b o t h a n a l y s e s . V a l u e s f o r t h e 30 cm depth a re - 20 -T a b l e 1. V a r i a t i o n o f s o i l b u l k d e n s i t y w i t h depth a t Sunset P r a i r i e f o r Codesa s o i l . (Mg m~3) Depth (cm) 5 15 25 35 45 55 80 100 Hertzman (1981) 1.2 1.35 1.5 1.55 1.6 1.6 1.6 1.6 D a v i s (1978) 1.52 1.75 T a b l e 2. S o i l w a t e r r e t e n t i o n c h a r a c t e r i s t i c s f o r Codesa s o i l a t Sunset P r a i r i e . S o i l Water Content S o i l M a t r i c P o t e n t i a l T -(M Pa) (kgH 20/kg s o i l ) (m3H20/jn s o i l ) -0.001 0.35+0.04 0.53+0.06 -0.01 0.28+0.02 0.43+0.03 -0.1 0.23+0.02 0.35+0.03 -1.5 0.16+0.03 0.24+0.05 - 21 -g i v e n i n T a b l e 2. These v a l u e s i n d i c a t e d a t o t a l s t o r a g e c a p a c i t y o f "~ 0.19 kg H 20/kg s o i l (0.001 t o 1.5 MPa), 3 wh i c h c o r r e s p o n d s t o a v o l u m e t r i c c a p a c i t y o f 0.29 m H 2 ^ ^ 3 . . m s o i l . 2. Measurements a) G e n e r a l program 1978: The f i e l d measurement program began May 28, and c o n t i n u e d u n t i l August 16. D u r i n g t h i s p e r i o d e i g h t s e t s of s o i l m o i s t u r e and p l a n t p r o d u c t i v i t y d e t e r m i n a t i o n s were made. Energy balance/Bowen r a t i o d a t a were c o l l e c t e d i n t e r m i t t e n t l y i n f o u r p e r i o d s t o t a l l i n g 38 days. 1979: The f i e l d measurement program began May 20 and c o n t i n u e d u n t i l August 24, w i t h Bowen r a t i o d a t a b e i n g c o l l e c t e d on 94 o u t o f 96 days. S o i l m o i s t u r e was measured a t l e a s t w e e k l y , and f o r a g e growth samples were t a k e n e v e r y two weeks. b) Forage growth Forage growth was measured by c l i p p i n g above-ground d r y m a t t e r from one square meter p l o t s . S t a n d i n g l i v e v e g e t a t i o n was h a r v e s t e d and d r i e d a t 80°C f o r 24 hours. In 1978, hay growth p l o t s were c u t from w i t h i n a 10 m by - 22 -15 m a r e a o f f a i r l y u n i f o r m v e g e t a t i o n . A monthly mowing program was e s t a b l i s h e d i n 1979 t o s i m u l a t e the g r a z i n g r o t a t i o n i n t h e s u r r o u n d i n g p a s t u r e . To measure p a s t u r e growth, t h r e e samples were c u t monthly a t each s i t e , i n c l u d i n g t h e f e r t i l i z e d and u n f e r t i l i z e d h a l v e s o f s i t e s 4 and 6. I n o r d e r t o p r o v i d e c o n t i n u i t y w i t h the 1977 and 1978 f i e l d seasons, samples o f d r y m a t t e r were t a k e n from uncut a r e a s a t s i t e s 1 and 7. Due t o c a t t l e b r e a k - i n s , t h e d a t a s e t s a t s i t e s 3 and 6 were n o t complete. Root p r o d u c t i o n was e s t i m a t e d by t a k i n g 7.5 cm d i a m e t e r c o r e s t o a d e p t h o f 60 cm, w h i c h r e p r e s e n t e d t h e e s t i m a t e d e x t e n t o f t h e r o o t ;zo.ne. Because o f t h e e x t e n s i v e a n a l y s i s r e q u i r e d , g e n e r a l l y no more th a n f o u r c o r e s were t a k e n e v e r y two weeks. Leaf a r e a i n d e x measurements were made on samples wh i c h were s e p a r a t e d a c c o r d i n g t o s p e c i e s . The p r o j e c t e d l e a f a r e a was measured u s i n g a H a y a s h i Denko Model AA-5 a u t o m a t i c p h o t o e l e c t r i c l e a f a r e a meter. c) S o i l m o i s t u r e I n 1978, g r a v i m e t r i c m o i s t u r e samples were t a k e n t o a depth o f 1.5 m a t t h e main s i t e . Samples were t a k e n from w i t h i n a 0.5m r a d i u s o f f i v e marked l o c a t i o n s . S i x samples were t a k e n between 0 and 10 cm each day f o r e s t i m a t i n g s o i l h eat c a p a c i t y . - 23 -In 1979, a T r o x l e r Model 1257 n e u t r o n meter was used t o make weekly s o i l m o i s t u r e measurements t o a depth of 1.5 m a t 4 o r 5 l o c a t i o n s a t a l l seven s i t e s . G r a v i m e t r i c samples were c o l l e c t e d from t h e 0 t o 10 cm l a y e r w i t h i n a r a d i u s o f 0.5 m from each a c c e s s t u b e . The v a l u e s o f g r a v i m e t r i c w a t e r c o n t e n t were c o n v e r t e d t o v o l u m e t r i c c o n t e n t (© ) u s i n g b u l k d e n s i t i e s from Hertzman e t a l . g i v e n i n T a b l e 1. The n e u t r o n meter was c a l i b r a t e d f o u r t i m e s d u r i n g t h e growing season by t a k i n g g r a v i m e t r i c p r o f i l e s o f s o i l w a t e r c o n t e n t near an ac c e s s tube f o r which r e a d i n g s had been made. Based on t h e l i m i t e d range o f m o i s t u r e c o n d i t i o n s e x p e r i e n c e d i n 1979, the c a l i b r a t i o n c u r v e drawn r e l a t i n g 9 t o n e u t r o n meter v count was c o n s i d e r e d v a l i d f o r 0.5 > 9 v > 0.23 (Hertzman ejt a l . , 1981). Root zone s t o r a g e was c a l c u l a t e d u s i n g n W = Z (Az.9 .) f o r r o o t zone' l a y e r . t h i c k n e s s Az. . , 1 v i i = l d) R a d i a t i o n S o l a r r a d i a t i o n measurements were made w i t h a K i p p and Zonen pyranometer mounted 1.5 m above ground l e v e l . A p a i r o f L i n t r o n i c pyranometers were mounted back-to-back a t 1.0 m, and used t o de t e r m i n e a l b e d o . Net r a d i a t i o n was measured w i t h a S w i s s t e c o SI p y r r a d i o m e t e r , purged w i t h dr y a i r . The r a d i o m e t e r s i g n a l was e l e c t r o n i c a l l y i n t e g r a t e d - 24 -f o r f i f t e e n minute p e r i o d s , and t h e pyranometers were r e a d e v e r y f i f t e e n m i n u t e s . The S w i s s t e c o and K i p p and Zonen i n s t r u m e n t s were c a l i b r a t e d by t h e N a t i o n a l R a d i a t i o n C e n t r e o f Environment Canada i n 1978, p r i o r t o t h e f i e l d season. The L i n t r o n i c pyranometers were checked a g a i n s t a l o c a l s t a n d a r d . e) S o i l h eat f l u x S u r f a c e s o i l heat f l u x was d e t e r m i n e d u s i n g two s o i l h eat f l u x p l a t e s i n s t a l l e d a t a depth o f 5 cm, a p p r o x i m a t e l y 1 m a p a r t , and c o r r e c t i n g f o r t h e r a t e o f h e a t s t o r a g e i n the 0-5 cm l a y e r . The l a t t e r was measured u s i n g two i n t e g r a t i n g thermometers, each c o n s i s t i n g o f f i v e d i o d e s i n s e r i e s , s e t i n t o a 10 cm l o n g epoxy r o d . In 197 8, germanium (1 N 2 326) d i o d e s were used, bu t i n 1979 t h e y were r e p l a c e d w i t h s i l i c o n (FD 300) d i o d e s . The s o i l h eat c a p a c i t y was d e t e r m i n e d by w e i g h t i n g the heat c a p a c i t i e s o f t h e w a t e r , m i n e r a l and o r g a n i c m a t t e r by t h e i r volume f r a c t i o n s and summing (de V r i e s , 1963). The volume f r a c t i o n s o f m i n e r a l and o r g a n i c m a t t e r i n t h e s u r f a c e l a y e r were r e p o r t e d by D a v i s (1978) t o be 0.567 and 0.014, r e s p e c t i v e l y . The volume f r a c t i o n o f w a t e r was o b t a i n e d by g r a v i m e t r i c s a m p l i n g and b u l k d e n s i t y measurement, w i t h v a l u e s i n t e r p o l a t e d f o r days between samples. - 25 -f) Bowen r a t i o The c a l c u l a t i o n o f t h e Bowen r a t i o and evapo-t r a n s p i r a t i o n a r e d i s c u s s e d i n s e c t i o n ( i ) . The f o l l o w i n g s e c t i o n d e s c r i b e s o n l y t h e i n s t r u m e n t a t i o n used. The p s y c h r o m e t r i c a p p a r a t u s and d a t a r e c o r d i n g system used t o measure t h e wet and d r y b u l b t e m p e r a t u r e g r a d i e n t s were used by D a v i s and d e s c r i b e d by B l a c k and McNaughton (1971) and Tang (1976). The system c o n s i s t e d o f two s e n s i n g heads, each h o u s i n g a wet and d r y - b u l b t e m p e r a t u r e s e n s i t i v e germanium (1 N 2326) d i o d e . The we t - b u l b s e n s o r s were s u p p l i e d w i t h d i s t i l l e d w a t e r v i a a c o t t o n s h o e l a c e w i c k w h i c h f e e d s from a r e s e r v o i r l o c a t e d on t h e s i d e of t h e h o u s i n g . The heads were t h e r m a l l y i n s u l a t e d w i t h p o l y u r e t h a n e , and r a d i a t i v e l y s h i e l d e d by w r a p p i n g w i t h a l u m i n i z e d m y l a r , and t h e s e n s o r s were a s p i r a t e d a t a r a t e > 3 m s ^ by a vacuum pump. The heads were l o c a t e d a t 1.0 and 2.0 m above the s o i l s u r f a c e , and r o t a t e d a u t o m a t i c a l l y e v e r y f i f t e e n m i nutes t o e l i m i n a t e s y s t e m a t i c e r r o r s i n t h e temp e r a t u r e d i f f e r e n c e measurement. The d i o d e s had a s e n s i t i v i t y o f 2.3 mV °C ^ and t h e i r s i g n a l was i n t e g r a t e d f o r t e n m i n u t e s , a f t e r a f i v e minute e q u i l i b r a t i o n p e r i o d f o l l o w i n g r o t a t i o n . The s e n s o r s were c a l i b r a t e d a t seven t e m p e r a t u r e s o v e r t h e range 7°C t o 35°C p r i o r t o t h e 1978 f i e l d season. They were r e c a l i b r a t e d a t - 26 -f i v e t e m p e r a t u r e s p r i o r t o t h e 1979 f i e l d season, f o l l o w i n g c i r c u i t r y m o d i f i c a t i o n s and r e p a i r work. g) Data r e c o r d i n g O p e r a t i n g p e r i o d s were g e n e r a l l y from 0500 u n t i l 2200 hours MST, e x c e p t d u r i n g r a i n f a l l o r maintenance p e r i o d s . P e r i o d i c a l l y , o p e r a t i o n s were c o n t i n u e d o v e r n i g h t , b u t t h i s was n o t done r o u t i n e l y because o f i n c r e a s e d g e n e r a t o r s e r v i c i n g r e q u i r e m e n t s . A l l e l e c t r o n i c s i g n a l s were t r a n s m i t t e d u s i n g s h i e l d e d s i g n a l c a b l e t o t h e d a t a l o g g i n g system l o c a t e d i n a t r a i l e r 50 m e a s t of t h e main s i t e . Power was p r o v i d e d by t h e grounded Onan d i e s e l g e n e r a t o r . The t r a i l e r t e m p e r a t u r e was m a i n t a i n e d above 10°C a t n i g h t , but s i n c e no c o o l i n g was a v a i l a b l e t h e d a t a l o g g i n g equipment was o c c a s i o n a l l y s u b j e c t e d t o t e m p e r a t u r e s o f 35 t o 40°C d u r i n g t h e daytime-.: -The wet and d r y b u l b d i f f e r e n c e s i g n a l s and t h e n e t r a d i a t i o n s i g n a l were i n t e g r a t e d by e l e c t r o n i c i n t e g r a t o r s as d e s c r i b e d by Tang (1976). P u l s e s from t h e i n t e g r a t o r s , produced a t a r a t e p r o p o r t i o n a l t o t h e i n p u t v o l t a g e , were r e c o r d e d by Sodeco c o u n t e r s w h i c h p r i n t e d e v e r y f i f t e e n m i n u t e s . A l l d i o d e t e m p e r a t u r e s , pyranometer s i g n a l s and the s o i l heat f l u x s i g n a l s were lo g g e d on a 20 c h a n n e l E s t e r l i n e - A n g u s r e c o r d e r w h i c h p r i n t e d s i m u l t a n e o u s l y w i t h t h e Sodeco c o u n t e r s . - 27 -h) Other m e t e o r o l o g i c a l measurements A B e l f o r t (Model 5780) w e i g h i n g r a i n g a u g e w i t h i t s o r i f i c e 90 cm above ground was used t o o b t a i n d a i l y r a i n f a l l amounts a t t h e main s i t e . A s t o r a g e gauge w i t h i t s o r i f i c e 30 cm above ground was l o c a t e d s e v e r a l meters away. In 1979, weekly p r e c i p i t a t i o n amounts were o b t a i n e d f o r a l l s i t e s u s i n g s t o r a g e gauges. A t the main s i t e , a Stevenson s c r e e n c o n t a i n i n g a r e c o r d i n g thermograph c a l i b r a t e d t o B.C. M i n i s t r y o f Environment network s t a n d a r d s was m a i n t a i n e d t h r o u g h o u t the g r o w i n g season. I n 1979, s i m i l a r thermographs were i n s t a l l e d a t the a u x i l i a r y s i t e s . B a r o m e t r i c p r e s s u r e measurements were o b t a i n e d from the A t m o s p h e r i c Environment S e r v i c e s t a t i o n a t F o r t S t . John A i r p o r t 50 km n o r t h o f Sunset P r a i r i e . i ) C a l c u l a t i o n o f e v a p o t r a n s p i r a t i o n The energy b a l a n c e o f a v e g e t a t e d s u r f a c e can be w r i t t e n : Q* = Q R + Q E + Q G (9) where Q and Q a r e t h e s e n s i b l e and l a t e n t heat f l u x H E d e n s i t i e s , r e s p e c t i v e l y , i f i t i s assumed t h a t h o r i z o n t a l - 28 -f l u x d i v e r g e n c e and canopy energy s t o r a g e r a t e s a r e n e g l i g i b l e . The f i r s t assumption i s u s u a l l y c o n s i d e r e d t o be v a l i d i f t h e f e t c h exceeds 10 0 t i m e s the measurement h e i g h t . The second assumption i s c o n s i d e r e d r e a s o n a b l e f o r s h o r t c r o p s , such as g r a s s e s ( ^ 0 1 1 1 , 1 9 7 5 ) . The Bowen r a t i o ( 8 ) i s d e f i n e d as t h e r a t i o o f t h e s e n s i b l e heat f l u x d e n s i t y t o t h a t o f t h e l a t e n t heat f l u x d e n s i t y , i . e . 8 = Q„/0_. By s u b s t i t u t i n g t h i s e q u a t i o n i n t o ( 9 ) , r e a r r a n g i n g , and d i v i d i n g by L, the evapo-t r a n s p i r a t i o n r a t e can be e x p r e s s e d a s : E = (Q* - Q_)/ ( 1 + 3 ) L (10) The Bowen r a t i o can be c a l c u l a t e d u s i n g (Fuchs and Tanner, 1970): -1 8 = [ (s/Y + 1) ( A T / A T ) - 1 ] (11) w where A T^ and A T a r e t h e wet and d r y - b u l b t e m p e r a t u r e d i f f e r e n c e s , r e s p e c t i v e l y , o v e r a v e r t i c a l d i s t a n c e w i t h i n t h e c o n s t a n t f l u x l a y e r . The p s y c h r o m e t r i c c o n s t a n t was e v a l u a t e d a t a i r tem p e r a t u r e f o r t h e h a l f hour p e r i o d , and c o r r e c t e d u s i n g t h e b a r o m e t r i c p r e s s u r e measured a t F o r t S t . John a i r p o r t . - 29 -When Bowen r a t i o s a r e near - 1 , l a r g e e r r o r s i n th e f l u x e s t i m a t e s can r e s u l t , s i n c e t h e denominator o f e q u a t i o n 10 approaches 0. F o l l o w i n g McNaughton and B l a c k (1973) and D a v i s (1978), f l u x e s were i n t e r p o l a t e d by eye f o r p e r i o d s when -1.5 <• g. <-0.5. Such p e r i o d s o c c u r r e d b r i e f l y i n the e a r l y morning and l a t e a f t e r n o o n when t h e p r o f i l e s changed from i n v e r s i o n t o l a p s e , and back, c o n t r i b u t i n g l i t t l e e r r o r t o t h e e v a p o r a t i o n t o t a l s r e p o r t e d , s i n c e t h e f l u x e s were s m a l l a t t h e s e t i m e s . In o r d e r t o o b t a i n e v a p o t r a n s p i r a t i o n t o t a l s , v a l u e s were i n t e r p o l a t e d f o r m i s s i n g p e r i o d s , u s i n g P r i e s t l e y and T a y l o r e s t i m a t e s when r a d i a t i o n d a t a were a v a i l a b l e . When th e P r i e s t l e y and T a y l o r f o r m u l a was used, v a l u e s o f a were chosen by comparison w i t h t h e n e a r e s t t i m e s f o r which v a l u e s were a v a i l a b l e . D a v i s (1978) compared e v a p o t r a n s p i r a t i o n r a t e s measured by t h e At m o s p h e r i c Environment S e r v i c e l y s i m e t e r a t Woodbridge, O n t a r i o , w i t h measurements made w i t h t h e Bowen r a t i o system used i n t h i s s t u d y . He found good agreement -2 w i t h s t a n d a r d e r r o r o f 30 W m f o r h a l f - h o u r l y v a l u e s , s t a t i n g t h a t e s t i m a t e s of E were w i t h i n +8% f o r d a i l y t o t a l s . Complete e r r o r a n a l y s i s f o r Bowen r a t i o c a l c u l a t i o n s o f e v a p o t r a n s p i r a t i o n r a t e a r e a v a i l a b l e (Fuchs & Tanner, 1970; B a i l e y , 1978; S p i t t l e h o u s e , 1981). - 30 -D. RESULTS AND DISCUSSION 1. P a s t u r e E v a p o t r a n s p i r a t i o n a) Energy b a l a n c e T y p i c a l energy b a l a n c e r e s u l t s f o r wet and d r y s o i l c o n d i t i o n s are shown i n F i g u r e s 2 and 3, r e s p e c t i v e l y . Appendix 1 shows daytime energy b a l a n c e components f o r 1978 and 1979. I n 1979, daytime Bowen r a t i o s ( Z Q„/ Z Q_, b o t h r l Jli summed over t h e p e r i o d Q* > 0) ranged from 0.05 t o 0.75, w i t h a s e a s o n a l average v a l u e ( Z Q / Z Q , b o t h summed H E o v e r t h e season) o f 0.39. I n 1978, daytime Bowen r a t i o s as h i g h as 1.24 were measured, but t h e s e a s o n a l average was o n l y 0.41. These v a l u e s compare w i t h a range o f 0.09 t o 0.73, and mean o f 0.32 f o r 1977 ( D a v i s , 1978). E a r l y i n 1979, v a l u e s Of Bowen r a t i o were f a i r l y h i g h , d e s p i t e c o o l c o n d i t i o n s , p o s s i b l y because'measurements began b e f o r e E was s i g n i f i c a n t , and E ... was l i m i t e d by s u r f a c e d r y i n g , s o x l The d a i l y s o i l heat f l u x d e c l i n e d from 20% t o 7% o f t h e n e t r a d i a t i o n f l u x as t h e season p r o g r e s s e d , because of t h e i n s u l a t i o n o f t h e s o i l s u r f a c e by t h e d e v e l o p i n g canopy. In b o t h 1978 and 1979 the s e a s o n a l average v a l u e o f t h e r a t i o Q~/Q* was 0.12, compared t o D a v i s ' r e p o r t e d v a l u e o f 0.09 i n 1977. T h i s d i f f e r e n c e i s r e a s o n a b l e , because t h e canopy was denser i n 1977, t h a n i n t h e two f o l l o w i n g y e a r s . - 31 -i 1 1 1 1 1 1 r SUNSET PRAIRIE PASTURE I 1 1 i i i i i i i i i i_ 0 4 8 12 16 20 24 TIME (MST) F i g u r e 2. Energy b a l a n c e components f o r J u l y 3, 197 8 under c o n d i t i o n s o f ample s o i l m o i s t u r e . Daytime Bowen r a t i o i s 0.16. - 32 -T 1 1 1 1 1 1 1 1 r SUNSET PRAIRIE PASTURE I I I I I I I I I 1 1 1 L 0 4 8 12 16 20 24 TIME (MST) F i g u r e 3. Energy b a l a n c e components f o r J u l y 25, 1978 under s o i l - l i m i t e d c o n d i t i o n s . Daytime Bowen r a t i o i s 1.05. - 33 -b) E n e r g y - l i m i t e d e v a p o t r a n s p i r a t i o n (E „) Daytime e v a p o t r a n s p i r a t i o n d a t a f o r 197 8 and 197 9 are p l o t t e d a g a i n s t r o o t zone s t o r a g e (W) i n F i g u r e 4. A l l v a l u e s o f E f o r W > 75 mm a r e c o n s i d e r e d t o be l i m i t e d o n l y by a v a i l a b l e energy, a l t h o u g h a few o f t h e v a l u e s f o r W <<r 75 mm and low E c o u l d be i n c l u d e d i n t h i s c a t e g o r y . max ^ 1 A r e g r e s s i o n o f daytime E v e r s u s daytime E was c a l c u l a t e d f o r a l l days w i t h W > ' 75 mm, w i t h the f o l l o w i n g r e s u l t , shown i n F i g u r e 5: E = 1.26 E - 0.01 mm d " 1 r 2 = 0.95 (12) Da v i s (1978) found a s l o p e o f 1.28 i n 1977 a t Sunset P r a i r i e . S i m i l a r v a l u e s were found f o r w e l l - w a t e r e d v e g e t a t i o n by Tanner and J u r y (1976), S t e w a r t and Rouse (1977), Mukammal and Neumann (1977). D e B r u i n and Keijman (1979) found a v a l u e o f 1.26 f o r t h e r a t i o E/E f o r Lake F l e v o , b u t c a l c u l a t e d eq a r e g r e s s i o n s l o p e of o n l y 1.17, w i t h a p o s i t i v e i n t e r c e p t o f 0.2 mm d A l t h o u g h t h e y c o n s i d e r e d t h i s i n t e r c e p t s i g n i f i c a n t , t h e y o f f e r e d no e x p l a n a t i o n f o r i t s e x i s t e n c e . The v a l u e o f 1.26 f o r a has been used t o draw t h e h o r i z o n t a l l i n e s r e p r e s e n t i n g E f o r d i f f e r e n t v a l u e s o f ^ ^ max E . The d a t a a r e s t r a t i f i e d a c c o r d i n g t o ranges o f E eq ^ ^ eq S i n c e t h e d a t a g e n e r a l l y f a l l w i t h i n t h e h o r i z o n t a l l i n e s - 34 -e 0 . 2 5 e 0 . 5 0 0 . 7 5 1 . 0 R A N G E O F E eq T T3 E UJ 6 1 9 7 8 1 9 7 9 ( n i m d - 1 ) A A o - 1 • o 1 - 2 • o 2 - 3 • • 3 - 4 E c = ba SUNSET PRAIRIE PASTURE ^ E m a x s 0cEeq • • • o -B— PC o o; • o o°u O D O 4 £ | 3 S" UJ • oo o o o 5 0 1 0 0 1 5 0 W (mm) 2 0 0 F i g u r e 4. Daytime e v a p o t r a n s p i r a t i o n f o r 1978 and 1979 v e r s u s r o o t z o n e s t o r a g e . H o r i z o n t a l l i n e s r e p r e s e n t v a l u e s o f E w i t h a = 1.26. Data p o i n t s a r e m a x s t r a t i f i e d by ranges o f E . S o i l l i m i t e d l i n e , E = be , u s e s e q b = 27 mmd - 1. s e - 35 -F i g u r e 5. Measured E v e r s u s E f o r 1978 and 1979 d a t a showing r e g r e s l i o n and 1:1 l i n e s . - 36 -b r a c k e t i n g t h e i r r e s p e c t i v e range, i t can be c o n c l u d e d t h a t E i s w e l l e s t i m a t e d u s i n g 1.26 as t h e v a l u e o f a . max 3 c) S o i l - l i m i t e d e v a p o t r a n s p i r a t i o n (E £) D u r i n g t h e 197 8 g rowing season E began a t the p o t e n t i a l r a t e ( i . e . E = E ) , but d e c l i n e d s i q n i f i c a n t l y ^ max ^ 2 a f t e r J u l y 20. V a l u e s o f E/E d e c l i n e d from 1.34 f o r 10 2 eq days i n e a r l y June t o 1.07 f o r 12 days i n l a t e J u l y , and 0.95 f o r 6 days i n mid-August. V a l u e s o f E f o r low s o i l m o i s t u r e c o n d i t i o n s a r e shown i n F i g u r e 4. A l i n e was f i t t e d by eye t o t h e p o i n t s r e p r e s e n t i n g s o i l - l i m i t e d e v a p o t r a n s p i r a t i o n as f o l l o w s : E = 6.7 (W - 35) = 27 9 (13) s e I n the f i g u r e , i s found t o be 35 mm (8 = 8%). No s o i l ^ min v m o i s t u r e l i m i t a t i o n i s e v i d e n t u n t i l 9 f a l l s below 25%, e w h i c h compares w i t h v a l u e s o f 80% and 40% used by S e l i r i o and Brown (1979) and B l a c k and S p i t t l e h o u s e (1980), r e s p e c t i v e l y , f o r c o a r s e r s o i l s . - 37 -d) E s t i m a t i o n o f e v a p o t r a n s p i r a t i o n From the p r e v i o u s two s e c t i o n s , i t can be seen t h a t (12)and (13) d e s c r i b e energy and s o i l l i m i t e d E. To e s t i m a t e E, t h e l e s s e r o f t h e v a l u e s g e n e r a t e d by (12) and (13) must be used. Hence, a p r o c e d u r e by w h i c h r o o t zone w a t e r s t o r a g e c o u l d be c a l c u l a t e d would be u s e f u l i n e s t i m a t i n g E. T h i s p r o c e d u r e w i l l be d i s c u s s e d f u r t h e r i n C h a p t e r 3. The p a r t i t i o n i n g o f E i n t o e v a p o r a t i o n and t r a n s p i r a t i o n i s d i s c u s s e d i n S e c t i o n D.3. 2. Dry M a t t e r P r o d u c t i o n a) V a r i a t i o n between y e a r s C u m u l a t i v e hay growth a t t h e main s i t e f o r 1977, 1978, and 1979 are shown i n F i g u r e 6. P r o d u c t i v i t y was h i g h e r i n 1977 t h a n i n e i t h e r 1978 o r 1979, p o s s i b l y because of an e a r l i e r s t a r t . T h i s e x p l a n a t i o n cannot be s u p p o r t e d by d a t a from t h e s i t e , s i n c e t h e c l i m a t e r e c o r d began on May 14, 1977, but growth was e v i d e n t by May 7, 1977, and had p r o b a b l y s t a r t e d a t l e a s t a week e a r l i e r . The 197 8 growing season appears t o have s t a r t e d l a t e r than i n 1977. Growth r a t e s i n 197 8 p a r a l l e l e d t h o s e o f 1977 u n t i l e a r l y J u l y , a f t e r w h i c h t h e y were much s l o w e r - 38 -F i g u r e 6. Accumulated hay growth a t s i t e 1 f o r 1977, 1978 and 1979 growing seasons. - 39 -p r o b a b l y due t o s o i l m o i s t u r e l i m i t a t i o n . I n 1979 growth began about one month l a t e r t h a n i n 1977, w i t h no new growth a p p e a r i n g u n t i l a f t e r May 20. Growth proceeded a t a p p r o x i m a t e l y the same r a t e as i n 1977, and matched 1978 p r o d u c t i o n by mid-August, d e s p i t e h a v i n g been o n l y h a l f as p r o d u c t i v e by e a r l y J u l y . The a p p a r e n t v a r i a b i l i t y i n 1977 growth r a t e s i s c h i e f l y due t o t h e n a t u r a l v a r i a t i o n s i n the p a s t u r e , w h i c h have been reduced i n 1978 and 1979 by c o n t i n u e d f e r t i l i z e r a p p l i c a t i o n . In 1979, t h e p a s t u r e was s t i l l g rowing a c t i v e l y by August 20, under c o n d i t i o n s o f ample s o i l m o i s t u r e , w h i l e senescence was o b s e r v a b l e i n 1978 under d r y c o n d i t i o n s . b) R e s u l t s o f g r a z i n g s i m u l a t i o n F i g u r e 7 compares t h e accumulated growth o f t h e s i m u l a t e d monthly g r a z i n g w i t h accumulated hay growth f o r s i t e s 1 and 7 (a n a t u r a l l y f e r t i l e s i t e ) i n 1979. Over t h e p e r i o d May 25 t o August 13, t h e c u t t i n g reduced growth by about o n e - t h i r d . Most of t h i s r e d u c t i o n o c c u r r e d d u r i n g t h e p e r i o d between t h e f i r s t and second c u t s . Growth o f t h e c u t f o r a g e was o n l y 40% o f t h a t o f t h e uncut f o r a g e d u r i n g t h i s p e r i o d , d e s p i t e adequate s o i l m o i s t u r e and i n s o l a t i o n . The r e d u c t i o n i n growth has s e v e r a l p o s s i b l e c a uses. F i r s t l y , mowing causes m e c h a n i c a l damage, and removal o f t h e a c t i v e l y - 40 -T 1 1 1 1 1 1979 SUNSET PRAIRIE PASTURE JUNE JULY AUGUST F i g u r e 7. Comparison o f accumulated growth o f uncut (hay) and c u t ( s i m u l a t e d p a s t u r e ) f o r a g e . V a l u e s a r e averages o f measurements a t s i t e s 1 and 7 w i t h range b a r s shown. - 41 -growing p o r t i o n o f the p l a n t , e x p o s i n g c h l o r o p h y l l - p o o r shade l e a v e s . S e c o n d l y , l e a f a r e a may be reduced below t h a t n e c e s s a r y f o r complete i n t e r c e p t i o n , o f a v a i l a b l e l i g h t . The e v a p o t r a n s p i r a t i o n measurements suggest t h a t t h e f i r s t e x p l a n a t i o n i s more l i k e l y s i n c e no r e d u c t i o n o f E was observed o v e r th e p a s t u r e a f t e r c u t t i n g and e x t e n s i v e g r a z i n g . Brougham (1956) found t h a t p a s t u r e c u t t o 7.5 cm s u f f e r e d p r o d u c t i v i t y r e d u c t i o n f o r s e v e r a l weeks a f t e r w a r d . A t l o w e r l a t i t u d e s , s e v e r a l w o r kers have ob s e r v e d t h a t s i m i l a r c u t t i n g regimes r e s u l t e d i n an i n c r e a s e i n p r o d u c t i v i t y compared w i t h uncut p l o t s . T h i s may be due t o t h e h i g h e r l e v e l s o f maintenance r e s p i r a t i o n i n t h e uncut s t a n d s (McCree, 1970), w h i c h s u b s t a n t i a l l y reduce net p r o d u c t i v i t y . A l t h o u g h t o t a l p r o d u c t i v i t y i s reduced by h a r v e s t i n g , the f o l i a g e i s younger and t h e r e f o r e l i k e l y t o be more p a l a t a b l e and o f h i g h e r q u a l i t y . The i n t e r a c t i o n o f y i e l d and q u a l i t y w i l l n o t be d i s c u s s e d but i t w i l l c e r t a i n l y a f f e c t d e c i s i o n s i n g r a z i n g management. H a r v e s t i n g r e s u l t e d i n v i s i b l e changes i n s p e c i e s dominance, s i n c e t h e mower removed t h e g r e a t e s t p r o p o r t i o n o f t h e t a l l e s t s p e c i e s . S i n c e t h i s s e l e c t i o n p r o c e s s i s d i f f e r e n t from t h a t e x e r t e d by c a t t l e g r a z i n g , s u s t a i n e d c u t t i n g c o u l d a f f e c t the s p e c i e s c o m p o s i t i o n o f the e x p e r i m e n t a l p l o t s , but t h i s was not c o n s i d e r e d t o be a s e r i o u s problem w i t h i n a s i n g l e growing season. - 42 -c) S p a t i a l v a r i a t i o n and e f f e c t s o f f e r t i l i t y The s p a t i a l v a r i a t i o n i n u n f e r t i l i z e d growth, shown i n F i g u r e 8 f o r 1979, was n o t g r e a t f o r most s i t e s , however, s i t e 7 growth was comparable t o t h a t o f the f e r t i l i z e d p o r t i o n s o f s i t e s 4 and 6. T h i s d i f f e r e n c e was e a s i l y o b s e r v e d by eye i n t h e f i e l d . The v a r i a t i o n s i n temperature and r a i n f a l l were s m a l l , and water was not c o n s i d e r e d l i m i t i n g i n 1979. I t i s p o s s i b l e t h a t s i t e 7 has a more f a v o u r a b l e n u t r i e n t regime t h a n the o t h e r s i t e s . The s i t e i s l o c a t e d 0.5 km from the r i d g e t o p , on a 5° s o u t h e r l y s l o p e , but t h e d i f f e r e n c e i n r a d i a t i o n from a l e v e l s i t e i s o n l y o f t h e o r d e r of 5% (Hay, 1979), w h i l e p r o d u c t i v i t y was v i r t u a l l y d ouble t h a t o f t h e o t h e r s i t e s . S i t e 6 was on a s i m i l a r s l o p e f a c i n g n o r t h , b u t s u f f e r e d no apparent p r o d u c t i v i t y l o s s compared w i t h o t h e r s i t e s . F e r t i l i z e r a p p l i e d a t s i t e s 4 and 6 r e s u l t e d i n almost 100% i n c r e a s e s i n y i e l d . The s i n g l e a p p l i c a t i o n o f 40-20-0 a t s i t e s 4 and 6 produced about 50% h i g h e r y i e l d t h an t h e t h r e e a p p l i c a t i o n s o f 30-0-0 a t s i t e 1. A t s i t e 1, t h e l a s t a p p l i c a t i o n was i n t h e f a l l o f 1978, and, u n l i k e s i t e s 4 and 6, was s u b j e c t t o l o s s e s t h r o u g h the w i n t e r . S i n c e the response t o phosphorus i s not g r e a t f o r t h i s s o i l s e r i e s , t h e d i f f e r e n c e s are thought t o be m a i n l y due t o t h e time o f a p p l i c a t i o n ( J . Dobb, p e r s o n a l communication). - 43 -F i g u r e 8. Comparison o f accumulated growth o f f e r t i l i z e d and u n f e r t i l i z e d c u t ( s i m u l a t e d p a s t u r e ) f o r a g e . Measurements a r e t h e average o f t h r e e r e p l i c a t e s a t s i t e s 4 and 6. Shaded a r e a shows range o f accumulated growth o f c u t , u n f e r t i l i z e d f o r a g e growth a t s i t e s 2 t o 6. - 44 -3. R e l a t i o n s h i p Between Growth and T r a n s p i r a t i o n a) R e l a t i o n s h i p w i t h e v a p o t r a n s p i r a t i o n F i g u r e 9 shows accumulated hay growth p l o t t e d a g a i n s t e v a p o t r a n s p i r a t i o n f o r 1977 and 1979. D a v i s (1978) r e p r e s e n t e d t h e smoothed 1977 d a t a by a power f u n c t i o n : G = 126 E 0 ' 7 1 3 + 2740 kg h a " 1 (where E i s the d a i l y e v a p o r a t i o n t o t a l i n mm). F u r t h e r a n a l y s i s i n d i c a t e d t h a t b o t h y e a r s can be s a t i s f a c t o r i l y r e p r e s e n t e d by l i n e a r e q u a t i o n s . A r e g r e s s i o n was c a l c u l a t e d f o r 1977 as f o l l o w s : G = 26.2 E (mm) + 3180 (kg ha" 1) r 2 = 0.821 (14) I f the summation o f E was s t a r t e d a t t h e b e g i n n i n g o f t h e growing season, a s m a l l n e g a t i v e v a l u e o f the i n t e r c e p t would be e x p e c t e d (Walker, 1978), s i n c e bare s o i l e v a p o r a t i o n must be s u b t r a c t e d . I f E were accumulated from May 1, r a t h e r t h a n June 7, a t an average r a t e o f 3 mm d 1 , t h e i n t e r c e p t would be 192 kg ha 1 r a t h e r t h a n 318 0. T h i s change i s r e p r e s e n t e d by t h e dashed l i n e i n F i g u r e 9, and s u p p o r t s t h e s u p p o s i t i o n t h a t growth began p r i o r t o May 1, i n 1977. S i n c e the energy b a l a n c e d a t a are i n c o m p l e t e f o r 1978, t h e r e l a t i o n s h i p cannot be v e r i f i e d f o r c o n d i t i o n s of water l i m i t a t i o n u n t i l a s a t i s f a c t o r y model i s d e v e l o p e d t o e s t i m a t e E. T h i s o b j e c t i v e w i l l be a d d r e s s e d i n t h e n e x t c h a p t e r . - 45 -ACCUMULATED E (mm) F i g u r e 9. Accumulated hay growth v e r s u s accumulated E f o r 1977 and 1979, showing s t a r t i n g d a t e s f o r summation of E. L i n e showing May 1 s t a r t i n g d a t e assumes average E of 3 mm d - 1 from May 1 t o June 7. - 46 -When hay growth was p l o t t e d a g a i n s t accumulated E f o r 1979, a s t r o n g l i n e a r r e l a t i o n s h i p was e v i d e n t , w i t h a c a l c u l a t e d r e g r e s s i o n as f o l l o w s : G = 26.2 E (mm) - 878 (kg ha" 1) r 2 = 0.999 (15) A n e g a t i v e i n t e r c e p t i s o b s e r v e d , as e x p e c t e d , s i n c e energy b a l a n c e measurements began b e f o r e t h e f i r s t g r e en l e a v e s emerged, and s i g n i f i c a n t e v a p o r a t i o n from t h e s o i l o c c u r r e d p r i o r t o canopy c l o s u r e . b) C o r r e c t i o n f o r bare s o i l e v a p o r a t i o n The d a t a from 197 9 suggest t h a t f u l l c o v e r was reac h e d a t a s t a n d i n g d r y m a t t e r w e i g h t o f I t ha \ which conforms t o a r e l a t i o n s h i p s u g g e s t i n g LAI = 2 G ( t ha "*") (Brougham, 1956). A v a l u e o f B = 1.5 was used i n (8) t o c o r r e c t f o r s o i l e v a p o r a t i o n w h i c h i s h i g h e r than t h e range o f v a l u e s g i v e n by Tanner and J u r y (1976) f o r row c r o p s (0.4-0.7). I t seems r e a s o n a b l e , though, t h a t g r a s s e s would p r o v i d e much more u n i f o r m c o v e r t h a n row c r o p s , and more e f f e c t i v e l y s u ppress s o i l e v a p o r a t i o n . When such a c o r r e c t i o n was made the r e l a t i o n s h i p between G and t r a n s p i r a t i o n was found t o be l i n e a r , w i t h a g r e a t l y reduced i n t e r c e p t , l e n d i n g s t r o n g - 47 -s u p p o r t t o deWit's (1958) concept o f an average growth/ t r a n s p i r a t i o n r a t i o w h i c h a p p l i e s d u r i n g a c t i v e growth. T h i s w i l l be u s e d , and d i s c u s s e d f u r t h e r i n C h a p t e r I I I . Such a r e l a t i o n s h i p does n o t account f o r senescence o f the v e g e t a t i o n , and c o u l d t h e r e f o r e n o t be a p p l i e d f o r t h e f u l l d u r a t i o n o f t h e growing season. No attempt has been made t o s e p a r a t e t h e c o n t r i b u t i o n s o f d i f f e r e n t s p e c i e s , so t h a t i f growth p a t t e r n s d i f f e r s i g n i f i c a n t l y , a d j u s t m e n t s may be needed t o account f o r s p e c i e s c o m p o s i t i o n . Data from the f o r a g e n u r s e r y a t Sunset P r a i r i e may be u s e f u l i n making such a d j u s t m e n t s . c) Comparison w i t h o t h e r s t u d i e s I f i t i s assumed t h a t s o i l e v a p o r a t i o n i s n e g l i g i b l e a f t e r canopy c l o s u r e , t h e n t h e s l o p e o f t h e r e g r e s s i o n ' l i n e c a l c u l a t e d i n (14) c o r r e s p o n d s t o d e W i t 1 s g r o w t h / t r a n s p i r a t i o n r a t i o . Any .overestimate of t h e t r a n s p i r a t i o n r a t e because of t h e i n c l u s i o n o f e v a p o r a t e d dew o r r a i n f a l l w i l l l e a d t o a p r o p o r t i o n a t e u n d e r e s t i m a t e i n t h e t r a n s p i r a t i o n r a t i o . The v a l u e o f 2 6 kg ha 1 p e r m i l l i m e t r e o f water t r a n s p i r e d f o r Sunset P r a i r i e , compares w i t h v a l u e s o f 22 found f o r E n g l a n d (Penman, 1962) and 19 f o r Denmark ( S t a n h i l l , 1960), b o t h of w h i c h a r e l o c a t e d a t s i m i l a r l a t i t u d e s t o t h a t of Sunset P r a i r i e . Rose e t a l . (1972) r e p o r t e d 8 and 14 kg - 48 -ha "Vmm H^O f o r d i f f e r e n t s t a g e s o f growth o f T o w n s v i l l e S t y l o a t 14.5°S i n A u s t r a l i a , w h i c h d i f f e r s s u b s t a n t i a l l y from S t a n h i l l ' s (1960) v a l u e o f 5.5 kg ha "Vmm H 20 f o r g r a s s e s i n I s r a e l . E. CONCLUSIONS Energy l i m i t e d e v a p o t r a n s p i r a t i o n can be e s t i m a t e d from the e q u i l i b r i u m p o t e n t i a l method u s i n g a = 1.26. S o i l l i m i t e d e v a p o t r a n s p i r a t i o n can be e s t i m a t e d as a f u n c t i o n o f r o o t zone w a t e r s t o r a g e . T r a n s p i r a t i o n can be c a l c u l a t e d as t h e l e s s e r o f (1) and (2) by c o r r e c t i n g f o r t h e e f f e c t s of bare s o i l e v a p o r a t i o n . A s t r o n g l i n e a r r e l a t i o n s h i p between hay growth and e v a p o t r a n s p i r a t i o n was ob s e r v e d . When a c o r r e c t i o n was made f o r s o i l e v a p o r a t i o n a l i n e a r r e l a t i o n -s h i p w i t h a much s m a l l e r i n t e r c e p t was found. S i m u l a t e d monthly g r a z i n g r e s u l t s i n h a l f t h e p r o d u c t i o n o f hay growth, and a l s o shows a l i n e a r r e l a t i o n s h i p w i t h e v a p o t r a n s p i r a t i o n . F e r t i l i z e r a p p l i c a t i o n c o n s i s t e n t w i t h l o c a l p r a c t i c e d o u b l e s n a t u r a l p r o d u c t i v i t y . - 49 -CHAPTER I I I . A SIMPLE MODEL FOR FORAGE GROWTH IN THE PEACE RIVER REGION A. INTRODUCTION Simple a g r o c l i m a t i c p r o c e d u r e s f o r e s t i m a t i n g p a s t u r e and hay growth r a t e s a r e i m p o r t a n t i n e v a l u a t i n g t h e a g r i c u l t u r a l p o t e n t i a l o f remote a r e a s . Models such as t h a t o f S e l i r i o and Brown (1979), w h i c h r e l y on an e x t e n s i v e d a t a base a r e n o t e a s i l y a p p l i e d i n a r e a s where s o i l , c l i m a t e , and c r o p response d a t a are s c a r c e . A model i s r e q u i r e d w h i c h needs o n l y s t a n d a r d s o i l and c l i m a t e d a t a , and w h i c h can be used e a s i l y by r e g i o n a l l a n d managers. I n o r d e r t o e s t i m a t e growth, t h e a v a i l a b i l i t y o f wat e r and energy t o t h e c r o p must be a s s e s s e d . S o l a r i r r a d i a n c e measurements a r e made r e l a t i v e l y e a s i l y , and can be e x t r a p o l a t e d o v e r f a i r l y l a r g e d i s t a n c e s . A s s e s s i n g t h e s o i l w a t e r s u p p l y t h r o u g h o u t t h e gr o w i n g season i s d i f f i c u l t s i n c e i t depends on t h e v a r i a b i l i t y o f p r e c i p i t a t i o n and s o i l w a t e r s t o r a g e c h a r a c t e r i s t i c s i n the a r e a o f i n t e r e s t . Growth can be r e l a t e d d i r e c t l y t o wa t e r s t o r a g e i n c o n d i t i o n s of s o i l w a t e r s u p p l y l i m i t a t i o n ( W i l l i a m s , 1970), o r t o s o l a r i r r a d i a n c e i n c o n d i t i o n s o f energy s u p p l y l i m i t a t i o n (Brouwer, 1956). T r a n s p i r a t i o n has been found t o be w e l l c o r r e l a t e d w i t h growth and t o i n c o r p o r a t e b o t h t h e - 50 -e f f e c t s of w a t e r and energy s u p p l y l i m i t a t i o n (Rose e t a l . , 1972). I n m o d e l l i n g e v a p o t r a n s p i r a t i o n , s e v e r a l w o r kers have used s o i l w a t e r c o n t e n t t o e s t a b l i s h w ater a v a i l a b i l i t y t o p l a n t r o o t s (Rose e t a l . , 1972; Rasmussen and Hanks, 1977; Feddes e t a l . , 1978; van K e u l e n , 1975; R u s s e l l , 1980). S e l i r i o and Brown (1978), and Walker (1978) used m o d i f i e d v e r s i o n s of t h e V e r s a t i l e S o i l M o i s t u r e Budget ( B a i e r e t a l . , 1979) i n t h e i r s i m u l a t i o n models. I n view o f t h e d i f f i c u l t y of a s s i g n i n g t h e parameters r e q u i r e d t o o p e r a t e t h e s e m u l t i p l e l a y e r models, i t was d e c i d e d t o use a s i m p l e r scheme based on a s i m p l e o n e - l a y e r model d e v e l o p e d by B l a c k e t aJL. (1970) f o r c a l c u l a t i n g changes i n r o o t zone water s t o r a g e d u r i n g t h e growing season. In t h i s c h a p t e r a s i m p l e model w h i c h uses s t a n d a r d d a i l y c l i m a t e d a t a i s d e v e l o p e d and e v a l u a t e d f o r c a l c u l a t i n g c r o p growth d u r i n g t h e growing season u s i n g a g r o w t h / t r a n s p i r a t i o n r a t i o . E v a p o t r a n s p i r a t i o n i s c a l c u l a t e d u s i n g s o l a r r a d i a t i o n and a i r t e m p e r a t u r e d a t a , and a o n e - l a y e r r o o t zone w a t e r b a l a n c e t o account f o r w a t e r s u p p l y l i m i t a t i o n . T r a n s p i r a t i o n i s c a l c u l a t e d by s u b t r a c t i n g e v a p o r a t i o n l o s s e s from the s o i l and f o l i a g e from t h e c a l c u l a t e d e v a p o t r a n s p i r a t i o n . The v a l i d i t y o f u s i n g s o l a r r a d i a t i o n , measured a t a r e g i o n a l c l i m a t e s t a t i o n , f o r c a l c u l a t i n g e v a p o t r a n s p i r a t i o n a t the s t u d y s i t e i s t e s t e d . B. THEORETICAL BASIS OF THE MODEL 1. E s t i m a t i n g T r a n s p i r a t i o n The e v a p o t r a n s p i r a t i o n r a t e (E) i s c a l c u l a t e d as the l e s s e r o f t h e energy and s o i l l i m i t e d r a t e s . The energy l i m i t e d r a t e ( E m a x ) i s c a l c u l a t e d u s i n g t h e P r i e s t l e y and T a y l o r (1972) approach on a daytime b a s i s , as f o l l o w s : F. Y = a [ s / ( s +Y)] (Q* - Q_)/L (1) where s, Y and L a r e t h e s l o p e o f the s a t u r a t i o n vapour p r e s s u r e c u r v e , t h e p s y c h r o m e t r i c c o n s t a n t , and t h e l a t e n t heat o f v a p o u r i z a t i o n , r e s p e c t i v e l y , a t t h e d a i l y mean a i r t e m p e r a t u r e , Q* i s t h e n e t r a d i a t i o n f l u x d e n s i t y , Q i s t h e G s o i l h e a t f l u x d e n s i t y ( - 0.1 Q*) and a i s d e t e r m i n e d e x p e r i m e n t a l l y . A n a l y s i s o f energy bblance/Bowen r a t i o d a t a f o r 1978 and 1979 i n d i c a t e d a daytime v a l u e o f 1.26 (see Cha p t e r I I ) , w h i c h w i l l be used i n t h e e v a p o t r a n s p i r a t i o n model. I n s o i l l i m i t e d c o n d i t i o n s E i s o f t e n r e l a t e d t o r o o t zone w a t e r c o n t e n t (Rasmussen and Hanks, 1977; Feddes e t a l . , 1978). I t was shown i n Ch a p t e r I I t h a t t h e s o i l l i m i t e d e v a p o t r a n s p i r a t i o n r a t e ( E s) c o u l d be e x p r e s s e d as f o l l o w s : - 52 -E s = b 9 e (2) where 9 g i s t h e f r a c t i o n o f e x t r a c t a b l e w a t e r i n t h e r o o t zone and b i s an e x p e r i m e n t a l l y d e t e r m i n e d c o e f f i c i e n t . 9 i s c a l c u l a t e d as f o l l o w s : e 9 = (W - W . )/(W - W . ) (3) e min max min v ' where W i s t h e r o o t zone water s t o r a g e , W i s t h e r o o t r max zone s t o r a g e a t s a t u r a t i o n , and W . i s t h e r o o t zone mm s t o r a g e a t wh i c h e v a p o t r a n s p i r a t i o n v i r t u a l l y c e a s e s . On the b a s i s o f d a t a from 197 8, the c o e f f i c i e n t b was ta k e n t o be 27 mm d 1 (see Chapter I I ) . The v a l u e o f b c o r r e s p o n d s t o PEMAX i n t h e model o f S e l i r i o and Brown (1979), and i s th e t h e o r e t i c a l maximum w a t e r s u p p l y r a t e f o r s o i l and v e g e t a t i o n when s t o r a g e e q u a l s W 3 3 ^ max Under s o i l l i m i t e d c o n d i t i o n s , the t r a n s p i r a t i o n r a t e (E^.) i s assumed t o be app r o x i m a t e d by E g , s i n c e t h e s o i l s u r f a c e i s u s u a l l y d r y under t h e s e c o n d i t i o n s and E ., approaches z e r o . Under energy l i m i t e d c o n d i t i o n s s o i l ^ J E^ _ i s c a l c u l a t e d u s i n g a p r o c e d u r e from Tanner and J u r y (1976) (see Ch a p t e r I I ) i n wh i c h (8) i s s u b t r a c t e d from E t o g i v e : max E t = Emax [ 1 " e x p (" B' L A I) ] (4) -. 53 -where B i s an e m p i r i c a l c o e f f i c i e n t and LAI i s the l e a f area index. Equation 4 i s based on the assumption t h a t the r a t i o of e v a p o r a t i o n from the s o i l (E .,) to E i s ^ s o i l p r o p o r t i o n a l t o the r a t i o of the net r a d i a t i o n exchange at the s o i l s u r f a c e t o t h a t above the canopy. I t w i l l tend to underestimate E^ somewhat as the s o i l d r i e s and e v a p o r a t i o n from the s o i l becomes s o i l - l i m i t e d . Values of B r e p o r t e d i n the l i t e r a t u r e vary from 0.47 f o r wheat (Denmead, 1973) to 0.69 f o r potatoes (Tanner and J u r y , 1976). The value chosen here was 1.5 to account f o r the dense grass canopy c o n t a i n i n g the b r o a d - l e a f a l s i k e c l o v e r . LAI of the crop was found t o be w e l l approximated as 2.0 G where G i s the accumulated forage growth ( i n tonnes per h e c t a r e ) . E v a p o t r a n s p i r a t i o n r a t e i s assumed not to be s i g n i f i c a n t l y a f f e c t e d by the presence of i n t e r c e p t e d r a i n f a l l , due t o the low aerodynamic roughness of the crop (Rutter, 1977). However, an estimate of i n t e r c e p t i o n i s necessary to estimate E- . I n t e r c e p t i o n i s c a l c u l a t e d u s i n g a f u n c t i o n g i v e n by Feddes e t a_l. (197 8) as: I = 0.55 P ( ° - 5 3 " ° - ° ° 8 5 ( P " 5 ) ) (5) where.P i s p r e c i p i t a t i o n i n m i l l i m e t r e s . T h i s f u n c t i o n approaches a maximum value of 1.85 mm. I n t e r c e p t e d r a i n f a l l - 54 -i s assumed t o e v a p o r a t e d i r e c t l y from t h e f o l i a g e a t t h e e n e r g y - l i m i t e d r a t e b e f o r e f u r t h e r t r a n s p i r a t i o n o c c u r s . T r a n s p i r a t i o n f o r t h e day f o l l o w i n g r a i n f a l l i s t h e r e f o r e e s t i m a t e d as t h e l e s s e r o f E minus i n t e r c e p t i o n , and E . max £- / s 2. E s t i m a t i n g Net R a d i a t i o n The n e t r a d i a t i o n exchange above the canopy can be e x p r e s s e d as f o l l o w s : Q*= ( 1 - r ) K + + L4- - L t (6) where r i s t h e c r o p r e f l e c t i o n c o e f f i c i e n t o r a l b e d o , K 4-i s t h e i n c o m i n g s o l a r r a d i a t i o n f l u x d e n s i t y and L4- and L-h are t h e incoming and o u t g o i n g longwave f l u x d e n s i t i e s r e s p e c t i v e l y : : On t h e b a s i s o f measurements made ov e r t h r e e growing s e a s o n s , the d a i l y average a l b e d o was found t o be a p p r o x i m a t e l y 0.25. The e f f e c t o f c l i p p i n g on t h e a l b e d o was n e g l i g i b l e . The d a i l y v a l u e o f L + - L + was d e t e r m i n e d u s i n g t h e s e m i - e m p i r i c a l approach proposed by L i n a c r e (1968) and m o d i f i e d by J u r y and Tanner (197 5 ) . T h i s approach used e s t i m a t e s o f L + and L + based on d a i l y average s c r e e n h e i g h t a i r t e m p e r a t u r e (T ) , and a c o r r e c t i o n f o r the e f f e c t a o f c l o u d s . S e v e r a l e m p i r i c a l methods have been d e v e l o p e d - 55 -t o c a l c u l a t e i n c o m i n g longwave r a d i a t i o n ( B r u n t , 1932; Swinbank, 1963; B r u t s a e r t , 1975; I d s o and J a c k s o n , 1969; S a t t e r l u n d , 1979). The e q u a t i o n d e v e l o p e d by Idso and J a c k s o n was used s i n c e i t has been found t o compare f a v o u r a b l y w i t h o t h e r methods over a wide range o f t e m p e r a t u r e s (Aase and I d s o , 1978; S a t t e r l u n d , 1979). The 4 e q u a t i o n g i v e s L i under c l e a r s k i e s as L+ = e a T where a a a i s t h e S t e f a n - B o l t z m a n c o n s t a n t and e i s t h e c l e a r a sky a t m o s p h e r i c e m i s s i v i t y as f o l l o w s : e = 1 - 0.261 exp (-7.77 x 1 0 4 T 2 ) ( T i n °C) (7) a a a Idso (1980) n o t e s t h a t the e q u a t i o n o v e r - e s t i m a t e s i n c o m i n g longwave r a d i a t i o n i n c o a s t a l and o c e a n i c e n v i r o n m e n t s , and s u g g e s t s t h a t t h i s may be due t o l o w e r d u s t l o a d s t h a n i n t h e d e s e r t environment f o r w h i c h the e q u a t i o n was d e v e l o p e d . The o u t g o i n g longwave r a d i a t i o n f l u x under c l e a r sky 4 c o n d i t i o n s was e s t i m a t e d u s i n g L+ = e aT where e i s s a s t h e c r o p s u r f a c e e m i s s i v i t y , assumed t o be 0.95 i n t h i s s t u d y . The f a c t o r used t o m u l t i p l y t h e c l e a r - s k y e s t i m a t e o f L+ - L+ t o g i v e an e s t i m a t e f o r c l o u d y c o n d i t i o n s i s as f o l l o w s ( L i n a c r e , 1968; J u r y and Tanner, 1975): c = a + b (K+ /K4- , ) (8) c l e a r where Ki i s t h e e x p e c t e d c l e a r day v a l u e o f incoming s o l a r r a d i a t i o n . The v a l u e s o f a and b were found t o be - 56 -0.1 and 0.9 r e s p e c t i v e l y , w i t h i n t h e range quoted by L i n a c r e (1968). I n summary, t h e d a i l y v a l u e o f n e t r a d i a t i o n was c a l c u l a t e d as f o l l o w s : Q* = (I^-.r)+:(\e;-e. )aT 4 [ 0.1+0. 9 (K+/K+ , J ] (9) a. S a. CXGcHT where r = 0.25, e =0.95 and e i s c a l c u l a t e d u s i n g (7) S cl 3. S o i l Water B a l a n c e A s o i l w a t e r b a l a n c e p r o c e d u r e was n e c e s s a r y t o e s t i m a t e d a i l y v a l u e s o f r o o t zone water s t o r a g e d u r i n g t h e growing s e a s o n , i n o r d e r t o c a l c u l a t e d a i l y e v a p o t r a n s p i r a t i o n r a t e . Root zone w a t e r s t o r a g e a t t h e end o f i t h day (W^) was e s t i m a t e d as f o l l o w s : W. =W. , + ( P . - E . - D . - R . ) A t (10) l l - l 1 1 1 1 V ' where i s t h e s t o r a g e o f t h e end o f t h e p r e v i o u s day, P^, E^, and R^ a r e t h e r a t e s o f r a i n f a l l , e v a p o t r a n s p i r a t i o n , d r a i n a g e and r u n o f f , r e s p e c t i v e l y , on day i , and A t i s t h e ti m e i n t e r v a l one day. E. i s det e r m i n e d by ( i ) c a l c u l a t i n g E from ( 1 ) , l 1 ^ max (7) and ( 9 ) ; ( i i ) c a l c u l a t i n g E 6. from (2) and (3) w i t h W. 1 JL and ( i i i ) t a k i n g t h e l e s s e r o f E and E . I n t h i s one-3 max s l a y e r model, water i s assumed t o be e q u a l l y a v a i l a b l e t o - 57 -th e c r o p r e g a r d l e s s o f i t s d i s t r i b u t i o n w i t h i n t h e r o o t zone. Based on r o o t d e n s i t y d a t a (Hertzman e t a l . , 1981) a s i n g l e r o o t zone d e p t h o f 450 mm was used f o r t h e e n t i r e growing season. P r o f i l e s o f r o o t zone w a t e r c o n t e n t f o r the 197 8 g rowing season a r e shown i n F i g u r e 1, i n d i c a t i n g t h a t t h e m a j o r i t y o f water e x t r a c t i n g i s from t h e t o p 600 mm. R a i n i s assumed t o f a l l a t t h e end o f t h e day, a f t e r e v a p o t r a n s p i r a t i o n has o c c u r r e d . S i n c e t h e m a j o r i t y o f summer r a i n f a l l e v e n t s a r e c o n v e c t i v e , t h i s w i l l o f t e n be r e a s o n a b l e , and i t does not a f f e c t the model o u t p u t s e r i o u s l y . D a i l y r a i n f a l l amounts from the r e c o r d i n g r a i n g a u g e were used, w i t h a 10% enhancement based on t h e t o t a l s from t h e two s t o r a g e gauges. Runoff can be g e n e r a t e d i n two ways. I f t h e r a i n f a l l r a t e exceeds t h e i n f i l t r a t i o n r a t e , t h e e x c e s s i s c o n s i d e r e d t o be Horton r u n o f f . I f the c a l c u l a t e d s o i l w a ter s t o r a g e exceeds w m a x ' the e x c e s s i s c o n s i d e r e d t o be Dunne r u n o f f . W_ „ was c a l c u l a t e d from b u l k d e n s i t y measurements t o be max J 48% by volume, o r 216 mm o f water s t o r a g e i n t h e r o o t zone. An i n f i l t r a t i o n r a t e o f 4 mm h 1 o b t a i n e d by Hertzman V . r : ( p e r s o n a l communication) was used. R a i n f a l l i s s e p a r a t e d i n t o amounts g r e a t e r and l e s s than 10 mm, w i t h l e s s e r amounts b e i n g c o n s i d e r e d c o n v e c t i v e , and g r e a t e r amounts f r o n t a l . C o n v e c t i v e r a i n s have an assumed d u r a t i o n o f 2 h o u r s , and f r o n t a l r a i n s a d u r a t i o n o f 8 h o u r s . U s i n g an i n f i l t r a t i o n r a t e o f 4 mm h \ Ho r t o n r u n o f f was seldom g e n e r a t e d . Dunne - 58 -F i g u r e 1. P r o f i l e s o f v o l u m e t r i c s o i l m o i s t u r e w i t h depth a t s i t e 1 d u r i n g t h e 1978 growing season. - 59 -r u n o f f was g e n e r a t e d l e s s f r e q u e n t l y than i n a l a y e r e d model wh i c h would p e r m i t t h e use o f lower d r a i n a g e r a t e s f o r deeper zones, a l l o w i n g r u n o f f t o o c c u r . Based on work by C a r d e r and Hennig (1966) on a s o i l o f s i m i l a r p h y s i c a l c h a r a c t e r i s t i c s a t B e a v e r l o d g e , A l b e r t a , i t was s u s p e c t e d t h a t d r a i n a g e and c a p i l l a r y r i s e were n e g l i g i b l e d u r i n g t h e growing season. T h i s i s r e a s o n a b l e , -3 s i n c e t h e b u l k d e n s i t y o f t h e subzone i s 1.8 Mg m i m p l y i n g low v a l u e s o f s a t u r a t e d c o n d u c t i v i t y . The i n i t i a l s o i l w a t e r c o n t e n t i s g e n e r a t e d i t e r a t i v e l y , by r u n n i n g t h e model from s a t u r a t i o n a t the s t a r t i n g d a t e t o t h e date o f t h e f i r s t s t o r a g e measurement, and a d j u s t i n g the i n i t i a l c o n t e n t by t h e amount o f t h e d i f f e r e n c e between t h e model o u t p u t and t h e measurement. A complete l i s t i n g o f the FORTRAN program used t o c a l c u l a t e t h e w a t e r b a l a n c e i s g i v e n i n Appendix 2. 4. R e l a t i o n s h i p Between Growth and T r a n s p i r a t i o n The model uses t h e g r o w t h / t r a n s p i r a t i o n r a t i o c o ncept (deWit, 19 58) t o c a l c u l a t e growth as f o l l o w s : n G = E m E (11) i i = l - 60 -where h i s t h e number o f days from the s t a r t o f t h e growing season, and m i s t h e g r o w t h / t r a n s p i r a t i o n r a t i o . Rose e t a l . (1972) used two v a l u e s o f m d u r i n g t h e growing season f o r Town s v i l l e S t y l o . Van K e u l e n (1975) c a l c u l a t e d the r a t i o d a i l y i n h i s p l a n t p h y s i o l o g i c a l model, but i n t h i s c h a p t e r an average v a l u e i s used, s i m i l a r t o van Keulen's s i m p l e r model. I n i t i a t i o n o f growth i s d i f f i c u l t t o s p e c i f y , s i n c e growth had a l r e a d y begun p r i o r t o t h e 1977 and 197 8 f i e l d seasons. I n t h i s s t u d y , i t was assumed, f o l l o w i n g S e l i r i o and Brown (1979), t h a t growth began on the f i r s t day f o l l o w i n g f i v e c o n s e c u t i v e days f o r w h i c h t h e mean s c r e e n ^ h e i g h t t e m p e r a t u r e exceeded 5°C. Hertzman e t a l . (1981) have found t h i s c r i t e r i o n i n a d e q u a t e under some c o n d i t i o n s , b u t i t i s a r e a s o n a b l e f i r s t a p p r o x i m a t i o n . In summary, the model c a l c u l a t e s E t h r o u g h o u t t h e season, u s i n g t h e l e s s e r o f t h e water and e n e r g y - l i m i t e d v a l u e s . T r a n s p i r a t i o n i s c a l c u l a t e d by c o r r e c t i n g f o r e v a p o r a t i o n from the b a r e s o i l and f o l i a g e , and (11) i s used t o c a l c u l a t e d r y m a t t e r as a f u n c t i o n o f t i m e . - 61 -C. EXPERIMENTAL SITE AND MEASUREMENTS F i e l d work was conducted a t t h e Sunset P r a i r i e Community P a s t u r e , 5 0 km s o u t h o f F o r t S t . John. The p a s t u r e i s d e s c r i b e d i n d e t a i l i n Ch a p t e r I I I . Seven 0.1 ha p l o t s i n a g r a z e d 250 ha tame p a s t u r e were used t o t e s t t h e w a t e r b a l a n c e model. Growth measured a t S i t e 1 was used t o t e s t t h e growth model. S i n c e t h e measurement program i s d e s c r i b e d i n Chapter I I , o n l y a b r i e f summary of measurements used i n d e v e l o p i n g and t e s t i n g t h e model i s p r e s e n t e d here. Both n e t and s o l a r r a d i a t i o n were measured a t t h e main s i t e d u r i n g t h e 1978 and 1979 f i e l d seasons. Albedo measurements were made w i t h upward and downward f a c i n g L i n t r o n i c pyranometers. I n 197 8, a K i p p s o l a r i m e t e r and i n t e g r a t i n g d a t a l o g g e r were i n s t a l l e d a t t h e F o r t S t . John a i r p o r t , making h o u r l y t o t a l s o f s o l a r r a d i a t i o n a v a i l a b l e on a r o u t i n e b a s i s . Daytime measurements were made u s i n g t h e i n s t r u m e n t a t i o n d e s c r i b e d i n Chapter I I , and by D a v i s (1978). The o p e r a t i n g p e r i o d s were from s u n r i s e t o sun s e t on an i n t e r m i t t e n t b a s i s i n 1978, and d a i l y from May 20 t o August 25 i n 1979. S o i l m o i s t u r e measurements were made e v e r y 5 t o 10 days, and f o l l o w i n g major r a i n f a l l e v e n t s i n b o t h 1978 and - 62 -1979. In 197 8 g r a v i m e t r i c methods were used t o o b t a i n s t o r a g e e s t i m a t e s f o r f i v e l o c a t i o n s a t t h e main s t u d y s i t e . I n 1979, t h e s t u d y i n c l u d e d s i x a d d i t i o n a l s i t e s i n an a r e a o f a p p r o x i m a t e l y 2 50 ha, and t h e n e u t r o n method was used t o o b t a i n measurements from 4 o r 5 a c c e s s tubes a t each s i t e , w i t h g r a v i m e t r i c samples b e i n g used f o r s u r f a c e l a y e r s . Forage growth was measured by hand c l i p p i n g t h e s t a n d i n g f o r a g e t o a h e i g h t o f a p p r o x i m a t e l y 5 0 mm i n 2 1 m sample p l o t s . I n 1979, t h r e e r e p l i c a t e samples were t a k e n from a r e a s mowed monthly. Hay growth was measured i n a f a i r l y u n i f o r m 10 m x 15 m uncut a r e a i n 1978 and 1979. D. RESULTS AND DISCUSSION 1. E s t i m a t i n g Net R a d i a t i o n Net r a d i a t i o n v a l u e s f o r 1979 c a l c u l a t e d by (9) f o r d a y l i g h t p e r i o d s were on average 4% h i g h e r t h a n measured v a l u e s . Idso (1980) r e p o r t s s i m i l a r o v e r e s t i m a t e s f o r a t m o s p h e r i c c o n d i t i o n s c l e a n e r than the s i t e f o r w h i c h (7) was d e v e l o p e d . S u b t r a c t i n g 0.03 from t h e c a l c u l a t e d a t m o s p h e r i c ; ; e m i s s i v i t y e l i m i n a t e d t h e o v e r e s t i m a t e f o r 1979 d a t a and t h i s p r o c e d u r e was adopted f o r t h e model. - 63 -T a b l e 1 shows the r e s u l t s o f u s i n g (9) t o e s t i m a t e Q* w i t h s o l a r r a d i a t i o n measured o n - s i t e and a t F o r t S t . John i n 1979, as w e l l as the r e s u l t s o f a r e g r e s s i o n between K+ and Q*. These r e s u l t s a r e f o r daytime t o t a l s o f n e t r a d i a t i o n . The s t a n d a r d e r r o r o f t h e p r e d i c t i o n s from (9) -2 -1 w i t h reduced was 0.65 MJ m d , w h i c h i s s l i g h t l y l o w e r t h a n t h a t f o r t h e r e g r e s s i o n between n et and s o l a r r a d i a t i o n measured a t the main s i t e on 67 days i n 1979 as f o l l o w s : Q* = 0. 565 K + - 0.27 MJ m~2 d " 1 r 2 = 0.97 (12) E q u a t i o n (9) would p r o v i d e b e t t e r Q* e s t i m a t e s t h a n (12) f o r s i t e s w i t h d i f f e r e n t a l b e d o s , and f o r t e m p e r a t u r e s beyond t h e range f o r w h i c h t h e r e g r e s s i o n was d e v e l o p e d . Tanner -2 -1 and J u r y (1975) r e p o r t e d Sy.x = 0.92 MJ m d u s i n g (9) f o r 24 hour p e r i o d s w i t h o u t a d j u s t i n g e . U s i n g s o l a r r a d i a t i o n from F o r t S t . John i n (9) w i t h r =0.25 and t; =0.95 r e s u l t e d i n an e r r o r o f s -2 -1 1.72 MJ m d . F i g u r e 2 shows Q* e s t i m a t e s u s i n g Sunset P r a i r i e and F o r t S t . John s o l a r r a d i a t i o n measurements i n (9) p l o t t e d a g a i n s t Q* v a l u e s measured a t Sunset P r a i r i e . I t i s e v i d e n t t h a t agreement i s g e n e r a l l y good u s i n g F o r t S t . John s o l a r r a d i a t i o n , w i t h o n l y s i x days h a v i n g e r r o r s -2 -1 g r e a t e r t h a n 2.0 MJ m d . A r e g r e s s i o n c a l c u l a t e d between T a b l e 1. Comparison o f s t a n d a r d e r r o r s o f n e t r a d i a t i o n e s t i m a t e s u s i n g the I d s o - J a c k s o n f o r m u l a , and a r e g r e s s i o n e q u a t i o n . (MJm~ 2d~ 1) (MJm 2 d _ 1 ) E s t i m a t i o n Method I n t e r c e p t S l o p e y:x K+ Sunset P r a i r i e I d s o - J a c k s o n , w i t h e c o r r e c t e d a R e g r e s s i o n o f Q* on K4-0.30 0. 27 0.973 0.978 0.979 0.971 0.57 0.66 K+ F o r t S t . John I d s o - J a c k s o n , e c o r r e c t e d a R e g r e s s i o n o f Q* on K4-1.69 2.04 0.834 0.825 1.52 0.767 0.790 1.69 Q* (estimated) = a + b Q* (measured) - 65 -M E A S U R E D Q* ( M J m ^ d " 1 ) F i g u r e 2. C a l c u l a t e d v e r s u s measured Q* u s i n g T measured o n - s i t e and KAmeasured o n - s i t e (SP) and a t F o r t S t . John ( F S J ) . - 66 -s o l a r r a d i a t i o n measured a t F o r t S t . John (FSJ) and a t Sunset P r a i r i e (SP) f o r 54 d a i l y t o t a l s i n 1979 y i e l d e d KMSP) = 0.88K+ (FSJ) + 1.48 MJ m ~ 2d _ 1 r 2 = 0.86 (13) U s i n g t h i s r e g r e s s i o n t o c a l c u l a t e v a l u e s o f s o l a r r a d i a t i o n from F o r t S t . John d a t a o n l y reduced the e r r o r from 1.72 -2 -1 t o 1.50 MJ m d , which i m p l i e s t h a t the d i f f e r e n c e s between t h e two s i t e s are m a i n l y random, and t h a t t h e dev e l o p e d i n t e r - s i t e c o r r e l a t i o n does l i t t l e t o improve p r e d i c t i o n a c c u r a c y . I t appears t h a t s o l a r r a d i a t i o n i s s p a t i a l l y w e l l - c o r r e l a t e d i n t h e r e g i o n , as would be ex p e c t e d ( S u c k l i n g and Hay, 1976), and t h a t t h e d a t a from F o r t S t . John c o u l d be u s e f u l i n e s t i m a t i n g Q* a t o t h e r l o c a t i o n s . A n a l y s i s o f t h e 1978 d a t a showed t h a t f o r t h e 35 days o f measurement, Q* e s t i m a t e s were b e t t e r than t h o s e f o r 1979. I n 1979, 47% of a l l e s t i m a t e s u s i n g (9) and (13) were a c c u r a t e t o w i t h i n 10%, w h i l e i n 197 8, 62% were w i t h i n 10%. D a v i s (1978) r e p o r t e d t h a t h i s c l o u d l a y e r model o v e r -p r e d i c t e d n e t r a d i a t i o n by 7%, and t h a t 41% o f h i s daytime e s t i m a t e s agreed t o w i t h i n 10%. Subsequent r e c a l i b r a t i o n o f the pyranometer used i n 1977 suggested t h a t the o v e r -e s t i m a t e was l e s s t h a n 2% ( D a v i s , p e r s o n a l communication). Measured and m o d e l l e d n et r a d i a t i o n v a l u e s f o r 1978 and 1979 are g i v e n i n Appendix 4. - 67 -2. Root Zone Water B a l a n c e a) S e a s o n a l r o o t zone s t o r a g e e s t i m a t e s The v a l u e s o f r o o t zone w a t e r s t o r a g e c a l c u l a t e d f o r t h e 1978 and 1979 growing seasons u s i n g t h e w a t e r b a l a n c e model w i t h W = 215 mm a r e compared w i t h measured max v a l u e s i n F i g u r e s 3 and 4. (Appendix 3 shows model e s t i m a t e s o f t h e w a t e r b a l a n c e terms and r o o t zone s t o r a g e . ) The p o s s i b l e e r r o r i n t h e s t o r a g e measurement was e s t i m a t e d t o be a p p r o x i m a t e l y + 5 mm. On t h e b a s i s o f t h i s f i g u r e , the maximum d i s c r e p a n c y o f t h e model v a l u e s was a p p r o x i m a t e l y 10 mm, and 75% o f t h e e s t i m a t e s were found t o be w i t h i n t h e p o s s i b l e e r r o r range of t h e measurement. T h i s c l o s e agreement l e n d s s u p p o r t t o the assumption t h a t d r a i n a g e d u r i n g most o f t h e growing season i n t h i s s o i l i s n e g l i g i b l e compared t o o t h e r water b a l a n c e terms. I n s e v e r a l cases t h e c a l c u l a t e d s t o r a g e v a l u e s are s e v e r a l days out o f phase w i t h measurements. T h i s i s p o s s i b l y due t o t h e use o f a t i m e s t e p o f one day i n s t e a d o f a s m a l l e r i n t e r v a l , o r t o t h e assumption t h a t r e d i s t r i b u t i o n o c c u r s i n s t a n t a n e o u s l y f o l l o w i n g heavy r a i n s . I n a wet y e a r , such as 1979, t h e c a l c u l a t i o n i s s e n s i t i v e t o the v a l u e o f s a t u r a t e d w a t e r s t o r a g e c a p a c i t y o f the r o o t zone (W ). A d e c r e a s e o f 4% i n s o i l p o r o s i t y max c J - 68 -10 20 31 10 20 30 10 20 31 10 20 31 MAY JUNE JULY AUGUST F i g u r e M o d e l l e d r o o t z o n e w a t e r s t o r a g e compared w i t h measured v a l u e s i n 1978. - 69 -F i g u r e 4. M o d e l l e d r o o t z o n e water s t o r a g e compared w i t h measured v a l u e s i n 1979. E f f e c t s o f u s i n g measured and m o d e l l e d Q*, and two v a l u e s o f maximum wa t e r s t o r a g e (W ) a r e shown. - 70 -r e s u l t s i n a de c r e a s e o f 15 mm i n W„ , . F i g u r e 4 shows max ^ t h a t t h e c o u r s e o f s o i l w a t e r s t o r a g e , u s i n g a v a l u e o f W x of 200 mm, i s between 4 and 15 mm l e s s t h a n t h a t u s i n g a v a l u e o f w m a x °f 215 mm. T h i s appears t o g i v e b e t t e r agreement w i t h t h e d a t a d u r i n g t h e l a t t e r p a r t of the growing season. The s p a t i a l v a r i a b i l i t y o f measured r o o t zone s t o r a g e o v e r t h e pasture i s shown i n Figure 5 and i n Table 2. The f i g u r e shows t h e cour s e o f s e a s o n a l v a l u e s o f s t o r a g e a t t h e s i x a u x i l i a r y s i t e s on the p a s t u r e , d u r i n g the 1979 growing season. Measured w a t e r s t o r a g e v a r i e s from 16 0 t o 220 mm when t h e s o i l i s wet, t o 80 t o 160 mm a f t e r s i g n i f i c a n t d r y i n g . S i t e s 2, 3 and 4 are l o c a t e d on h i g h ground, whereas 5, 6 and 7 a r e on lower ground. The h i g h v a l u e s f o r s i t e 5 a r e somewhat s u r p r i s i n g , but may be due t o runon from u p s l o p e a r e a s near s i t e 4. A l s o shown i n F i g u r e 5 are t h e c o u r s e s o f water s t o r a g e c a l c u l a t e d u s i n g t h e model w i t h t h e i n i t i a l w a t e r s t o r a g e s e q u a l t o t h e v a l u e s f o r June 1 a t s i t e s 7, 2 and 4 c o r r e s p o n d i n g t o the upper, m i d d l e and lower l i n e s r e s p e c t i v e l y . These c o u r s e s a r e p a r a l l e l , because t h e same r a i n f a l l i s used (see Ch a p t e r I I ) , and e v a p o r a t i o n i s n o t s o i l l i m i t e d a t any of the s i t e s , so e x t r a c t i o n proceeds at t h e same r a t e . T a b l e 2. Rootzone s t o r a g e d a t a f o r 1978 and 197 9. ( v a l u e s i n mm are the mean o f 4 o r 5 r e p l i c a t e s ) . 1978 1979 Sample Date S i t e 1 Sample Date S i t e 4 May 31 188 May 30 178 177 164 150 199 166 197 June 7 152 June 7 168 168 158 136 14 159 164 152 125 187 162 170 23 134 22 139 146 137 112 171 143 154 29 98 122 108 84 163 119 128 J u l y 2 149 115 J u l y 4 85 4 164 154 146 138 186 161 200 9 1 9 140 110 1 z 17 l o o 194 191 176 173 20 52 22 172 175 169 158 202 175 197 25 178 139 28 163 161 156 129 182 153 164 Aug. 1 65 Aug. 3 144 114 161 134 145 8 159 130 12 43 11 152 141 137 114 173 139 154 15 135 95 17 82 19 149 139 136 118 163 142 141 22 154 107 25 157 148 145 109 F i g u r e 5. S p a t i a l v a r i a t i o n i n measured and m o d e l l e d r o o t z o n e w a t e r s t o r a g e i n 1979. The upper, m i d d l e , and lower l i n e s r e p r e s e n t model runs u s i n g i n i t i a l v a l u e s on June 1 from s i t e s 7, 2, and 4 r e s p e c t i v e l y . - 73 -I n g e n e r a l , t h e model g i v e s a good i n d i c a t i o n o f the changes i n s o i l w a ter s t o r a g e d u r i n g t h e growing season, w i t h e x c e p t i o n o f s i t e 5 d u r i n g t h e f i r s t d r y i n g p e r i o d . I t appears t h a t knowledge o f t h e range o f i n i t i a l m o i s t u r e c o n d i t i o n s l e a d s t o r e a s o n a b l e p r e d i c t i o n s o f t h e subsequent co u r s e of r o o t zone s t o r a g e . A l t h o u g h t h i s would not be t r u e i n a r e a s o f more extreme topography, i t i s p r o b a b l y a p p l i c a b l e t o much of t h e l a n d u t i l i z e d "for tame p a s t u r e and hay i n t h e r e g i o n . The s o i l m o i s t u r e model i s p r o b a b l y a c c u r a t e f o r most of the growing season, a l t h o u g h t h e v a l u e of a might be h i g h e r f o r c o o l e r autumn c o n d i t i o n s (DeBruin and K e i j m a n , 1979). I f t h e model i s used as a s i t e i n d e x i t i s p r o b a b l y more p r a c t i c a l t o o b t a i n an i n i t i a l m o i s t u r e c o n t e n t measurement t h a n t o attempt t o s i m u l a t e the p r o c e s s e s o f s n o w d r i f t i n g and snowmelt i n o r d e r t o model e a r l y s p r i n g c o n d i t i o n s . b) E s t i m a t i n g e v a p o t r a n s p i r a t i o n and t r a n s p i r a t i o n The g e n e r a l agreement between measured and m o d e l l e d v a l u e s o f W i n F i g u r e s 3, 4 and 5 i n d i c a t e s t h a t t h e e v a p o t r a n s p i r a t i o n model i s a c c e p t a b l y a c c u r a t e . Agreement d u r i n g p e r i o d s when d r a i n a g e i s known t o be s m a l l g i v e s s t r o n g s u p p o r t t o t h e e v a p o t r a n s p i r a t i o n model. - 74 -There was no t e s t o f t h e e s t i m a t e s o f cr o p t r a n s p i r a t i o n from (4) u s i n g LAI and e v a p o t r a n s p i r a t i o n . Over the f i r s t t h r e e weeks o f t h e 197 9 growing season when t o t a l E was 70 mm, E was c a l c u l a t e d t o be 32 mm. W h i l e the a c c u r a c y o f t h e l a t t e r e s t i m a t e i s n o t h i g h , c o n s i d e r a b l e e r r o r would r e s u l t i f t r a n s p i r a t i o n was assumed e q u a l t o e v a p o t r a n s p i r a t i o n . S i m i l a r l y , i n t h e f i r s t week f o l l o w i n g c u t t i n g as much as 10 mm o f e v a p o r a t i o n from t h e s o i l c o u l d o c c u r . However, f o r much o f the t i m e (when LAI > 1.5) E t - E. R a i n f a l l on d r y s o i l r e s u l t s i n an uneven d i s t r i b u t i o n o f w a t e r w i t h i n t h e p r o f i l e w h i c h cannot be s i m u l a t e d i n a s l a b model. The i n t e r c e p t i o n f u n c t i o n p r o v i d e s a degree o f r e a l i s m , s i n c e i n t e r c e p t e d w a t e r i s e v a p o r a t e d a t t h e energy l i m i t e d r.ate:before f u r t h e r demand i s p l a c e d on the s o i l . These problems c o u l d be a l l e v i a t e d , but a t t h e expense of t h e model's s i m p l i c i t y . C u r r e n t l y t h e model can be o p e r a t e d u s i n g a hand-held c a l c u l a t o r , but f o r some a p p l i c a t i o n s f u r t h e r s o p h i s t i c a t i o n may be n e c e s s a r y . 3. E s t i m a t i n g Growth From E v a p o t r a n s p i r a t i o n F i g u r e 6 shows t h e measured and c a l c u l a t e d v a l u e s o f accumulated hay growth a t t h e main s i t e f o r 197 8 and 1979, based on a g r o w t h / t r a n s p i r a t i o n r a t i o o f 0.026 t ha "V - 75 -F i g u r e 6. M o d e l l e d accumulated growth compared w i t h measured v a l u e s a t s i t e 1. Growth/ t r a n s p i r a t i o n r a t i o s used i n c a l c u l a t i n g uncut (hay) and c u t ( s i m u l a t e d p a s t u r e ) growth were 0.026 and 0.013 t ha - 1mm _ 1 r e s p e c t i v e l y . - 76 -mm H^ O. Measurement e r r o r i s e s t i m a t e d ; t o be +0.2 5 t h a ~ x . and c a l c u l a t e d v a l u e s g e n e r a l l y f a l l w i t h i n t h i s range. I f e v a p o t r a n s p i r a t i o n had been used i n s t e a d o f t r a n s p i r a t i o n i n t h e growth r e l a t i o n s h i p , growth o f hay o r p a s t u r e would be o v e r e s t i m a t e d by more th a n 100% i n the f i r s t t h r e e weeks o f the growing season. I t was found t h a t a g r o w t h / t r a n s p i r a t i o n r a t i o o f 0.013 t ha "'"/mm was r e q u i r e d t o c a l c u l a t e accumulated growth of f e r t i l i z e d p a s t u r e (mowed monthly) a t s i t e 1 ( F i g u r e 5 ) . T h i s r a t i o i s an averag e , and may be a r e s u l t o f a lower g r o w t h / t r a n s p i r a t i o n r a t i o i n t h e f i r s t week f o l l o w i n g mowing, w i t h a g r a d u a l r e c o v e r y t o t h e h i g h e r r a t i o f o r hay growth. The y i e l d s o f t h e u n f e r t i l i z e d s i m u l a t e d p a s t u r e s i t e s ( 2 - 5 ) , w h i c h r e p r e s e n t t h e m a j o r i t y o f t h e p a s t u r e , were b e s t p r e d i c t e d by a g r o w t h / t r a n s p i r a t i o n r a t i o o f 0.008 t ha - 1/mm. In 1978, e a r l y senescence reduced p r o d u c t i v i t y below the l e v e l p r e d i c t e d f o r August. T h i s weakness of t h e model r e s t r i c t s i t s u s e f u l n e s s t o p e r i o d s o f a c t i v e growth. The d e c r e a s e o f p r o d u c t i v i t y which o c c u r s d u r i n g senescence has been w e l l documented (e.g. B i s c o e e t a l . , 1975; Byrne and T o g n e t t i , 1969) but s i m p l e c l i m a t o l o g i c a l c r i t e r i a f o r i t s o n s e t have n o t . The growing degree-day f u n c t i o n used by S e l i r i o and Brown (1979) i n t h e i r model d i d n o t account f o r t h i s e a r l y senescence. They used a s i g m o i d growth c u r v e - 77 -which approached a maximum y i e l d o f 12 t ha x ( i n Southern O n t a r i o ) . T h e i r model, based on accumulated growing degree days above 5°C p r e d i c t e d t h a t the c r o p was c l o s e r t o senescence i n 1979 than i n 1978, which i s c o n t r a r y t o measurements and v i s u a l o b s e r v a t i o n s . Doyle and F i s h e r (1979) i n c o r p o r a t e d t h e e f f e c t o f s o i l l i m i t e d w a t e r uptake by wheat i n a s i m p l e e q u a t i o n f o r t h e t r a n s p i r a t i o n r a t i o : m = a t 2 - b(E /E ) (15) s max where t i s t h e time from a c r i t i c a l growth s t a g e . The use of such an e q u a t i o n w o u l d h e l p t o account f o r t h e r e d u c t i o n i n growth o b s e r v e d i n 1978, b u t t h e e q u a t i o n does n ot account f o r t h e i r r e v e r s i b l e r e d u c t i o n i n growth r a t e w h i c h accompanies senescence. E. CONCLUSIONS The s e a s o n a l c o u r s e o f r o o t zone w a t e r s t o r a g e a t Sunset P r a i r i e P a s t u r e can be c a l c u l a t e d u s i n g a s i n g l e s l a b w a t e r b a l a n c e model w h i c h r e q u i r e s o n l y s o i l r e t e n t i o n c h a r a c t e r i s t i c s , i n i t i a l r o o t zone w a t e r c o n t e n t and r e g i o n a l c l i m a t e d a t a . E v a p o t r a n s p i r a t i o n from d r y o r wet p a s t u r e can be e s t i m a t e d w e l l u s i n g the P r i e s t l e y -- 78 -T a y l o r (1972) approach w i t h a daytime a o f 1.26. T r a n s p i r a t i o n can be e s t i m a t e d from E and p a s t u r e growth (Tanner and J u r y , 1976). Net r a d i a t i o n , r e q u i r e d f o r e s t i m a t i o n o f E can be m o d e l l e d t o w i t h i n + 15% u s i n g o n - s i t e a l b e d o and a i r t e m p e r a t u r e d a t a , and s o l a r r a d i a t i o n measured a t F o r t S t . John. The c o u r s e o f accumulated hay and p a s t u r e growth can be e s t i m a t e d u s i n g the g r o w t h / t r a n s p i r a t i o n r a t i o approach (Rose e t al_. , 1972) . The r a t i o i s a f f e c t e d by f e r t i l i t y , and the v a l u e used f o r p a s t u r e i s h a l f t h a t f o r hay. - 79 -CHAPTER IV. SUMMARY AND CONCLUSIONS Based on r e l a t i o n s h i p s d e v e l o p e d from r e s e a r c h conducted d u r i n g t h r e e growing seasons, a s i m p l e c l i m a t e -based model i s proposed t o d e s c r i b e f o r a g e growth a t t h e Sunset P r a i r i e Community P a s t u r e i n t h e Peace R i v e r r e g i o n o f B r i t i s h C olumbia. The model, w h i c h i s based on a l i n e a r r e l a t i o n s h i p between growth and t r a n s p i r a t i o n , d e s c r i b e s t h e c o u r s e o f f o r a g e growth under l i m i t a t i o n s o f t e m p e r a t u r e , e v a p o r a t i v e demand and water a v a i l a b i l i t y . I n t h e model, growth i s i n i t i a t e d a f t e r f i v e c o n s e c u t i v e days w i t h mean a i r t e m p e r a t u r e e x c e e d i n g 5°C. T h i s c r i t e r i o n i s g e n e r a l l y a c c u r a t e t o w i t h i n one week, and can be c a l c u l a t e d u s i n g d a t a from e x i s t i n g c l i m a t e s t a t i o n s i n t h e r e g i o n . E v a p o t r a n s p i r a t i o n used i n t h e growth model, i s c a l c u l a t e d as t h e l e s s e r o f energy and s o i l l i m i t e d r a t e s . The c a l c u l a t i o n o f t h e energy l i m i t e d r a t e (E ) r e q u i r e s ^ max ^ knowledge o f t h e a v a i l a b l e energy, t h e a i r t e m p e r a t u r e , and a , t h e r a t i o o f ^ m a x t o the e q u i l i b r i u m e v a p o r a t i o n r a t e . Because o f i t s h i g h s p a t i a l c o r r e l a t i o n i n t h e r e g i o n , s o l a r r a d i a t i o n measured a t F o r t S t . John can be used t o c a l c u l a t e n e t r a d i a t i o n a t t h e Sunset P r a i r i e Community P a s t u r e . Temperature d a t a r e q u i r e d i n t h i s c a l c u l a t i o n a r e a v a i l a b l e f o r t h e community p a s t u r e s i n t h e r e g i o n . S i n c e a and t h e - 80 -al b e d o a re c o n s e r v a t i v e f o r a r e a s o f s i m i l a r v e g e t a t i o n , the c a l c u l a t i o n o f E i s w e l l s u i t e d t o a l a r q e max 3 homogeneous a r e a such as t h e Peace R i v e r r e g i o n . The c a l c u l a t i o n o f t h e s o i l l i m i t e d evapo-t r a n s p i r a t i o n r a t e (E g) r e q u i r e s more s i t e s p e c i f i c d a t a t h a n does t h e c a l c u l a t i o n o f E . The r e l a t i o n s h i p between max ^ E g and r o o t zone w a t e r c o n t e n t depends on t h e v e g e t a t i o n c h a r a c t e r i s t i c s and on t h e water r e t e n t i o n p r o p e r t i e s o f the s o i l . The model r e q u i r e s s p e c i f i c a t i o n o f t h e parameter b, which i s t h e r a t i o o f E g t o t h e f r a c t i o n o f e x t r a c t a b l e w a t e r i n t h e r o o t zone (9 ). C a l c u l a t i o n o f 9 r e q u i r e s e e ^ knowledge o f t h e upper and lower l i m i t s o f r o o t zone water s t o r a g e (W and W . , r e s p e c t i v e l y ) . ^ max mm ^ 1 The d a i l y r o o t zone water budget, which i s used t o de t e r m i n e t h e degree and d u r a t i o n o f s o i l water l i m i t a t i o n , r e q u i r e s knowledge o f r o o t zone water s t o r a g e a t t h e b e g i n n i n g o f t h e growing season, t h e v a l u e o f w m a x ' t h e i n f i l t r a t i o n r a t e , and d a i l y t o t a l r a i n f a l l and E . I n max many models t h e i n i t i a l water s t o r a g e i s assumed t o e q u a l W„ , b u t t h i s a s s u m p t i o n may s e r i o u s l y reduce t h e a c c u r a c y max J o f model p r e d i c t i o n s i n y e a r s w i t h l i g h t snowpack o r d r y s p r i n g c o n d i t i o n s . I f a r e g i o n a l f o r a g e growth model were t o be implemented, c o n s i d e r a t i o n s h o u l d be g i v e n t o measuring s o i l w a t e r s t o r a g e on a weekly o r monthly b a s i s d u r i n g t h e growing season. The a r b i t r a r y s e p a r a t i o n o f r a i n f a l l i n t o - 81 -c o n v e c t i v e and f r o n t a l e v e n t s c o n t r i b u t e s as much t o t h e c a l c u l a t e d r u n o f f as does t h e i n f i l t r a t i o n r a t e s p e c i f i e d . Any work t o improve t h i s p o r t i o n o f t h e model s h o u l d t h e r e f o r e examine b o t h r a i n f a l l c l i m a t o l o g y and s o i l c h a r a c t e r i s t i c s . E v a p o r a t i o n from b a r e s o i l and from f o l i a g e i s s e p a r a t e d from t r a n s p i r a t i o n u s i n g e m p i r i c a l r e l a t i o n s h i p s w h i c h have n o t been v e r i f i e d f o r t h e r e g i o n . T e s t s o f t h e model suggest t h a t t h e form o f t h e s e r e l a t i o n s i s not c r i t i c a l , b u t t h a t t h e i r f u n c t i o n s c o n t r i b u t e s i g n i f i c a n t l y t o t h e a c c u r a c y o f t h e growth c a l c u l a t i o n s . S i n c e t h e parameters i n t h e s e r e l a t i o n s h i p s r e p r e s e n t c h a r a c t e r i s t i c s o f the v e g e t a t i o n , t h e y a r e p r o b a b l y a p p l i c a b l e on a r e g i o n a l b a s i s . The g r o w t h / t r a n s p i r a t i o n r a t i o s o b t a i n e d a t Sunset P r a i r i e a p p l y t o t h e f o r a g e m i x t u r e and f e r t i l i z e r l e v e l s p r e s e n t . S i n c e t h e o t h e r community p a s t u r e s i n t h e r e g i o n a r e seeded w i t h s i m i l a r m i x t u r e s , t h e model can be a p p l i e d i f t h e f e r t i l i z e r r esponse i s a c c o u n t e d f o r . A l t e r n a t i v e l y , t h e model can be used t o c a l c u l a t e f o r a g e growth under t h e c l i m a t e c o n d i t i o n s p r e v a i l i n g a t a n o t h e r p a s t u r e , u s i n g the g r o w t h / t r a n s p i r a t i o n r e l a t i o n s h i p d e v e l o p e d f o r Sunset P r a i r i e . T h i s a l l o w s d i r e c t comparison o f t h e c l i m a t i c p o t e n t i a l a t s e v e r a l s i t e s , e x c l u s i v e o f t h e e f f e c t s o f f o r a g e m i x t u r e , f e r t i l i t y l e v e l , and s o i l t i l l a g e . - 82 -The use of a senescence f u n c t i o n based on c r o p a g i n g and w a t e r l i m i t a t i o n would s i g n i f i c a n t l y e xtend t h e p e r i o d f o r w h i c h t h e model c o u l d be r e a l i s t i c a l l y a p p l i e d . Because o f t h e l a c k o f f i e l d d a t a l a t e i n t h e growing season, no g e n e r a l f u n c t i o n was d e v e l o p e d i n t h i s t h e s i s . However, use of t h e s i m p l e f u n c t i o n d e s c r i b e d i n Chapter I I I s i g n i f i c a n t l y improved t h e model p r e d i c t i o n s d u r i n g August 197.8, when wa t e r l i m i t a t i o n s i n i t i a t e d e a r l y senescence. I n g e n e r a l , model e s t i m a t e s o f e v a p o t r a n s p i r a t i o n , s o i l w a t e r s t o r a g e , and f o r a g e growth a r e good, c o n s i d e r i n g the l i m i t e d , d a t a r e q u i r e d f o r t h e i r c a l c u l a t i o n . C u r r e n t l y , t h e model i s q u i t e r e a l i s t i c , i n t h a t t h e major p h y s i c a l p r o c e s s e s w h i c h a f f e c t t h e p l a n t a r e d e s c r i b e d . A number o f improve-ments c o u l d be made t o t h e model, i n p a r t i c u l a r ( i ) c h a r a c t e r i z a t i o n o f s o i l s and c r o p s i n t h e r e g i o n i s r e q u i r e d t o implement t h e model, ( i i ) improvement o f t h e c r i t e r i o n used t o i n i t i a t e growth, ( i i i ) q u a n t i t a t i v e d e s c r i p t i o n o f f e r t i l i z e r r e s p o n s e . I n a d d i t i o n , t h e i n t e r a c t i o n o f g r a z i n g f r e q u e n c y and i n t e n s i t y i s e x t r e m e l y complex, and m e r i t s f u r t h e r i n v e s t i g a t i o n . P r e l i m i n a r y work u s i n g an e m p i r i c a l m u l t i p l i e r t o a c c o u n t f o r t h e r e d u c t i o n o f f o r a g e growth from monthly c u t t i n g i s p r o m i s i n g , b u t i t i s not known whether d i f f e r e n t c u t t i n g h e i g h t s and f r e q u e n c i e s can be m o d e l l e d . F u r t h e r work on t h i s problem s h o u l d i n c o r p o r a t e t h e q u a l i t y o f t h e f o r a g e , w h i c h i s e x t r e m e l y i m p o r t a n t i n p a s t u r e - 83 -management. M o d e l l i n g such i n t e r a c t i o n s r e q u i r e s d e t a i l e d knowledge o f t h e p h y s i o l o g y o f t h e p l a n t s , and c o n s i d e r a b l y more d a t a t h a n c o u l d be c o l l e c t e d i n t h i s p r o j e c t (e.g. r a t e s o f p h o t o s y n t h e s i s and r e s p i r a t i o n , p a r t i t i o n i n g o f p h o t o s y n t h e t i c p r o d u c t s ) . Any a t t e m p t t o improve t h e m o d e l l i n g o f t h e e f f e c t s o f d i f f e r e n t e n v i r o n m e n t a l c o n d i t i o n s and management p r a c t i c e s must be judged b o t h i n terms o f t h e a c c u r a c y and r e p r e s e n t a t i v e n e s s o f t h e model e s t i m a t e s . - 84 -LITERATURE CITED Aase, J.K. and S.B. Idso. 1978. A comparison of two formula types f o r c a l c u l a t i n g long-wave r a d i a t i o n from the atmosphere. Water Resour. Res. 14: 623-625. A r k l e y , R.J. 1963. 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M e t e o r o l . 21: 93-109. Youngner, V.B. and F . J . Nudge. 1976. S o i l t e m p e r a t u r e , a i r te m p e r a t u r e and d e f o l i a t i o n e f f e c t s on growth and n o n - s t r u c t u r a l c a r b o h y d r a t e s o f Kentucky B l u e g r a s s . Agron. J . 68: 257-260. - 90 -APPENDIX 1. D a i l y Energy Balance Components f o r 1978 and 1979. 1 9 7 8 D A I L Y E N E R G Y B A L A N C E C O M P O N E N T S THE FOLLOWING IS A SUMMARY OF DAILY TOTAL AND AVERAGE VALUES AS FOLLOWS: I h-' I THE FLUX DENSITIES ARE IN UNITS OF MJ M-2 D-1 AND TEMPERATURES ARE IN DEGREES CELCIUS DAY OSTAR GZERO QHEAT OEVAP BOWEN ALPHA P & T c w SUMOE SUMO* SUMPT SUMKD KDOWN ABDO TDBAR TSBAR DLTD DLTV 158 13 07 2 93 2 84 7 30 0 39 1 20 7.65 0 45 7 3 13 1 7 7 -0 0 -0 00 0 0 18 9 10 7 0 19 0 17 159 13 43 1 53 5 04 6 86 0 74 1 03 8 . 36 0 58 14 2 26 5 16 0 -0 0 - 0 00 0 0 14 4 9 9 0 16 0 14 160 10 20 1 60 4 01 4 58 0 88 0 98 5.89 0 53 18 7 36 7 21 9 -0 O - 0 00 0 0 1 1 3 9 0 0 17 0 17 SUM 36 70 6 07 1 1 90 18 74 O 63 1 08 21 .90 0 53 18 7 36 7 21 9 - 0 0 - 0 00 3 00 14 9 9 9 0 17 0 16 DAY OSTAR GZERO OHEAT OEVAP BOWEN ALPHA P & T °l W SUMOE SUMO* SUMPT SUMKD KDOWN ABDO TDBAR TSBAR DLTD DLTV 174 1 1 30 2 25 2 63 6 42 0 41 1 24 6.54 0 38 6 4 1 1 3 6 5 - 0 0 - o 00 0 0 13 5 12 8 0 15 0 20 176 6 58 1 12 0 62 4 84 0 13 1 44 4 . 23 0 39 1 1 3 17 9 10 8 14 5 14 53 0 26 20 0 17 0 0 1 1 0 28 177 15 98 2 14 2 1 1 1 1 76 0 18 1 41 10. 52 0 34 23 0 33 9 21 3 37 8 23 29 0 26 18 3 15 7 0 13 0 20 178 15 42 1 92 1 60 12 03 0 13 1 47 10. 30 0 41 35 1 49 3 31 6 62 1 24 31 0 27 18 3 15 9 0 10 0 12 179 16 17 2 36 2 09 1 1 72 0 18 1 36 10.86 0 26 46 8 65 4 42 4 87 8 25 65 0 26 20 6 16 9 0 09 0 29 180 13 60 2 09 1 25 10 26 0 12 1 40 9.25 0 34 57 0 79 0 51 7 108 5 20 75 0 25 21 5 17 2 0 15 0 23 181 10 15 1 22 1 80 7 13 0 25 1 26 7.15 0 24 64 2 89 2 58 8 123 2 14 70 0 25 16 8 16 6 0 14 0 13 182 15 25 1 27 3 54 10 42 0 34 1 33 9.87 0 27 74 6 104 4 68 7 148 3 25 12 0 27 15 6 15 5 0 17 0 19 183 16 16 1 81 2 52 1 1 84 0 21 1 38 10.82 0 21 86 4 120 6 79 5 173 7 25 37 0 27 19 1 16 1 0 13 0 30 184 15 83 2 03 1 88 1 1 93 0 16 1 38 10.91 0 18 98 3 136 4 90 4 198 0 24 34 0 26 21 0 17 5 0 15 0 18 185 16 03 1 97 3 98 10 08 0 40 1 1 1 1 1 .44 0 17 108 4 152 5 101 9 221 7 23 71 0 25 20 5 18 5 0 19 0 21 SUM * * * * * 20 18 24 03 # # # # * 0 22 1 34 ***** 0 17 108 4 152 5 101 9 221 7 ***** 0 26 18 7 16 3 0 14 0 21 DAY: THE JULIAN CALENDAR DAY NUMBER OSTAR: THE NET RADIATION FLUX DENSITY GZERO: THE SOIL HEAT FLUX DENSITY AT THE SURFACE OHEAT: THE SENSIBLE HEAT FLUX DENSITY QEVAP: THE LATENT HEAT FLUX DENSITY BOWEN: THE DAILY BOWEN RATI0(QHEAT/QEVAP) ALPHA: THE RATIO OF EVAPORATION/ EQUILIBRIUM EVAPORATION P & T : THE CALCULATED PRIESTLEY-TAYLOR EVAPORATION WITH ALPHA = 1.26 WATER: THE FRACTIONAL VOLUMETRIC WATER CONTENT OF THE O TO 10 CM LAYER SUMOE: THE SUM OF OEVAP FOR THE PERIOD SUMO*: THE SUM OF OSTAR FOR THE PERIOD SUMPT: THE SUM OF P & T FOR THE PERIOD SUMKD: THE SUM OF KDOWN FOR THE PERIOD KDOWN: THE SHORTWAVE RADIATION FLUX DENSITY ABDO: THE SURFACE ALBEDO TDBAR: THE AVERAGE DAYTIME DRY BULB TEMPERATURE TSBAR: THE AVERAGE SOIL TEMPERATURE IN THE O TO 5 CM LAYER DLTD: THE AVERAGE DRY BULB TEMPERATURE OVER 1 METER DLTW: THE AVERAGE WET BULB TEMPERATURE DIFFERENCE OVER 1 METER 0 c/l ro ro to ro ro ro o C/l r o r o r o r o i o r o r o r o r o r o r o r o r o r o a c I O 10 IO IO IO IO > c - - - ' - - - O O O O O O O O O O > 2 - j co oi 4-. co ro -< 3 c o r o - . o c D c n - 4 c n o i 4 - c o r o - . o -< C J o o 00 cn cn - - - - cn cn (/> * i o - . r o c o - ^ c n r o c o c o o r o c o o - i CO -1 * -•• co A cn cn > * O u i f f l O m - J - i C n ^ O O l D O O > ro co o - - - J cn ui X I o i u i c n j _ o o o i c n _ . 4 - u i - i c n c D a i CJ CO O O - O O O N -J I M ro io cn io --. co cn 70 oo O r o A o i - . o o c o c n o c o - j ^ 4 - j a i 70 f O _. co o O Ol 4 - 4 - o i o r o t o - . u i - - ^ i o i 4 - o i o O _ _ O 4 - O o i Q * O M M I 01 A u u u u - i & c n u u u c o - i - ' I CO oo oi -•• ~ J oo to > ro ~ - 4 - C O C 0 C 0 a i 0 0 - . 0 1 O C 0 - ~ l O 1 4 - > 4- j - 4- co co 4- H CD C D r o a i o o o o r o c o r o - - c o c n o o r o - - 4 -1 O o CO co 4- cn —. ro co m —_ c n c n o o o o - 4 c o c n o i o i c n - 4 0 o c n * - m < < oo O O O O co ro > A . o o o o 4 - - . c n c o c o o o _ . o 0 4 ^ o o c o > cn 00 CO Ol CO CO -0 c o c o c o o i ~ 4 _ . o o 4 - r o o i r o * . o i c o O O O O O - O 00 O O O O O O O O - O O O O O O 00 O O cn co cn - 4 ro cn £ cn c n o i c o 4 - c o 4 - c o o - 4 0 i 4 - 4 - r o r o ~j O ~4 00 4- 00 m _ . _ . O O i r o c o c o - _ o i o o o o o i i o c o m 2 z o - O O - O O > _ _ - . - . - . - . - . - - O O O - ' - ' - - - - ' > CO O CD CO O -J CO T> o - O u - i - i O - ^ ( D O O O u i o "O cn oo o co oo oo cn I - 4 _ . o o o o i c o - 4 c n o o c n o i i o - j C D o i I > > IO "0 CD co cn - J - - co 4- ~ - i o o o o o o o o c o o o c o c n - 4 0 o c D c n o i a= C» IO cn cn cn io - j ro ^ i O c o c o o c o c o 4 - - - 4 i o c n c D c n o CO CO CD -J CD 00 - i * o i - . 4 - O c o o c o c o o o - 4 c n o i o o c o H o O O O O O O o O O O O O O O O O O O O O O _ - - - O - - O - ro u - i U i o u u O - i O - i O O - ^ cn oi - 4 co oo cn s: O O 4 _ o i 4 - c o c n c o - . c n o c o - j r o i o -_ -_ -4. 01 CD c o o o - j c n c n o i o i 4 - c o c o r o r o - i . C/l CO co cn io cn oi co c _ . - . 4 - ^ l C O - . C 0 0 4 - O O C O - 4 0 - * 0 1 C s CO co cn - i cn cn co o 01 o i c n - g c o r o c n c o c o u i 4 - c o c o c o o O r r i rn CO CO CO IO — C/l cn o i 4 _ c o _ . o c o c n - 4 c n c n 4 - c o _ - cn 00 oo co oi co cn c cn o i c o - ' C o a i i i C n c n i o c o c o - . - j ' H c 2 2 4- co o cn -g O # 4- 4 - 4 - o o o o c o c n ^ - c o - . - . 0 - ' - ' O IO ro ro -J- l/l o O O C D o o - j c n c n c n j - c o c o r o - . 00 cn cn ro ~j co oo 4- c CD o o o r o c o 4 - c n r o c o 4 - - J O - - - - o i c 2 IO ro cn o co - - co — . - - c o c o 4 - c n o i a i o o j - c n c o ~ 4 - j O "0 -i -1 IO cn cn cn A io io _•. C/l Ol o i c o _ . C D ^ i o i t » r o o c n - 4 c n i o - . C/l cn cn - J co 4- io o c - 4 - 4 c n c n o i o i c n ~ j c o o o c o _ ' _ . - j - - . c _. 3 O O cn o - J io ro 7\ CO o o 4 - 4 - o i - - r o 4 - 4 - o c n - 4 c o o o r o o O cn _ _ _ _ # r o - . r o i o _ i . - . I O - . - . I O I O - . - . cn oo 4- oo ro ro o # — c o o o o o o o o o — a o - 4 0 c o c n - - X a * a O u - j u i n O a # 4 - C D C D 4 - C 0 - 4 O C 0 C 0 C 0 4 - 4 - O l r O a IO cn cn -4 - - cn oo * _ . - 4 C O O - 4 - l C n C D C 0 0 0 O C 0 C 0 O l z Z O > O O O O O O O O O O O O O O O O O O O O O > > IO io ro ro io io io co M l o t o i o r o r o t o r o r o r o r o r o r o i o r o cn co cn oi ro A oi a cn 0 1 0 1 4 - 4 - 0 1 4 - 4 - 4 - - J - J 0 1 4 - 4 - 0 1 o o o _ » . _ * . H _ _ _ . _ . _ . _ . - _ _ . i o r o - . i o r o r o _ i . - - H CO ro cn oi oo - - - j O co c o ~ j - j - 4 c n 4 i O - - - o o - - c o - _ c o c o O 00 D-cn O -- O ro - J CD > -4 4 - ^ i o o - j ~ 4 0 o - - O c o c o r o 4 - - j - - > 70 _ . —* _i. -1 4- CO 01 CO CO 01 1^ C/l ~4 - 4 - 4 - 4 ~ j c n c n c n - 4 - j - 4 o o o o c n - i C/l co ca 00 oo co co cn io > Ol O c n o i ~ 4 c n ~ 4 r o c o o - 4 0 i c n o i c n > 70 xi O O O O O O O O O O O O O O O O O O O O O O a o —- — . _ . _ . _>. _ . M r o _ . r o r o - - . - . | o c o i o - i . r o r o _ - _ . i— cn A oo io o - J cn H O b C o d O - J A - j - i U t t i O - f c H a a O O O O O O O o O O O O O O O O O O O O O O a o — . - i . - i . I O _ . _ i . - * r - ro r o - - r o r o i o - - r o r o - - - - r o r o r o r o i -cn ro cn io ro co cn H ro 4 - c o - . c o c o 4 - - - o i c D c n o ^ 4 c o 4 - H E - 26 1 9 7 9 D A I L Y E N E R G Y B A L A N C E C O M P O N E N T S THE FOLLOWING IS A SUMMARY OF DAILY TOTAL AND AVERAGE VALUES AS FOLLOWS: DAY : THE OSTAR THE GZERO THE OHEAT THE OEVAP THE BOWEN THE ALPHA THE P & T THE WATER THE SUMQE THE SUMO* THE SUMPT THE SUMKD THE KDOWN THE ABDO : THE TDBAR THE TSBAR THE DLTD : THE DLTW : THE JULIAN CALENDAR DAY NUMBER NET RADIATION FLUX DENSITY SOIL HEAT FLUX DENSITY AT THE SURFACE SENSIBLE HEAT FLUX DENSITY LATENT HEAT FLUX DENSITY DAILY BOWEN RATIO(OHEAT/OEVAP) RATIO OF EVAPORATION/ EQUILIBRIUM EVAPORATION CALCULATED PRIESTLEY-TAYLOR EVAPORATION WITH ALPHA = 1.26 FRACTIONAL VOLUMETRIC WATER CONTENT OF THE 0 TO 10 CM LAYER SUM OF OEVAP FOR THE PERIOD SUM OF OSTAR FOR THE PERIOD SUM OF P & T FOR THE PERIOD SUM OF KDOWN FOR THE PERIOD SHORTWAVE RADIATION FLUX DENSITY SURFACE ALBEDO AVERAGE DAYTIME DRY BULB TEMPERATURE AVERAGE SOIL TEMPERATURE IN THE 0 TO 5 CM LAYER AVERAGE DRY BULB TEMPERATURE OVER 1 METER AVERAGE WET BULB TEMPERATURE DIFFERENCE OVER 1 METER ^ 5 U) THE FLUX DENSITIES ARE IN UNITS OF MJ M-2 D-1 AND TEMPERATURES ARE IN DEGREES CELCIUS DAY OSTAR GZERO OHEAT OEVAP BOWEN ALPHA P S T WATER SUMOE SUMQ* SUMPT SUMKD KDOWN ABDO TDBAR TSBAR DLTD DLTW 139 5 16 0 41 3 61 1 09 3 30 0 46 2 97 0 49 1 1 5 2 3 0 -o 0 - 0 00 0 0 10 3 5 7 0 23 0 15 140 1 76 0 52 0 10 1 08 0 09 2 04 0 67 0 49 2 2 6 9 3 6 -0 0 -o 00 0 0 8 0 5 3 0 01 0 01 141 5 23 -O 63 4 22 1 65 2 56 0 55 3 79 0 49 3 8 12 1 7 4 -0 0 - 0 00 0 0 12 1 6 8 O 25 0 16 142 10 20 2 01 4 28 3 91 1 09 0 81 6 1 1 0 49 7 7 22 4 13 5 - 0 0 - 0 00 0 0 19 6 9 4 0 25 0 19 143 6 62 1 23 2 70 2 69 1 00 0 85 3 97 0 49 10 4 29 0 17 5 -0 0 - 0 00 0 0 16 8 8 6 0 10 0 10 145 10 57 1 51 5 37 3 69 1 46 0 72 6 43 0 49 14 1 39 5 23 9 17 1 17 10 0 28 15 4 9 7 0 21 0 14 146 6 61 1 20 2 24 3 16 0 71 1 03 3 87 0 49 17 3 46 1 27 8 28 2 1 1 14 0 28 13 5 8 9 0 09 0 10 148 10 81 1 03 4 08 5 70 0 71 1 26 5 72 0 49 23 0 57 0 33 5 48 5 20 31 0 40 7 1 5 3 0 12 O 15 149 6 34 1 06 1 90 3 45 0 55 1 30 3 35 0 49 26 4 63 3 36 9 60 3 1 1 78 0 27 6 6 6 0 0 07 0 09 150 12 97 2 73 4 02 6 22 0 65 1 08 7 29 0 49 32 7 76 3 44 2 83 3 23 00 0 30 14 7 9 3 0 17 0 18 151 1 1 94 2 05 2 87 7 40 0 39 1 21 7 68 0 49 40 1 88 2 51 8 103 0 19 72 0 29 14 4 1 1 1 0 07 0 14 152 10 17 1 83 2 28 6 09 0 37 1 24 6 19 0 49 46 1 98 4 58 0 1 19 8 16 81 0 29 15 9 1 1 6 0 13 0 1 1 153 10 06 1 58 2 41 6 06 0 40 1 22 6 24 0 49 52 2 108 4 64 3 135 4 15 59 0 29 15 7 10 8 0 09 0 12 154 13 68 1 95 3 63 8 1 1 0 45 1 22 8 35 0 49 60 3 122 1 72 6 158 7 23 23 0 29 15 7 1 1 7 0 15 0 19 155 10 09 1 49 3 02 5 58 0 54 1 18 5 96 0 49 65 9 132 2 78 6 174 9 16 28 0 29 14 3 10 9 0 12 0 15 156 2 67 0 19 -0 69 3 17 -0 22 2 33 1 71 0 48 69 1 134 9 80 3 178 3 3 38 0 27 10 7 10 5 - 20 0 38 157 8 93 1 29 4 35 3 29 1 32 0 84 4 92 0 48 72 3 143 8 85 2 195 8 17 46 0 27 10 0 10 6 0 14 0 12 158 6 54 1 63 1 19 4 01 0 30 1 26 4 01 0 47 76 4 150 3 89 2 215 4 19 63 0 29 12 1 10 3 0 0 0 0 159 14 77 1 82 4 38 8 58 0 51 1 26 8 59 0 46 84 9 165 1 97 8 238 8 23 42 0 28 12 3 11 4 0 17 0 24 DAY OSTAR GZERO OHEAT OEVAP BOWEN ALPHA P & T WATER SUMOE SUMO* SUMPT SUMKD KDOWN ABDO TDBAR TSBAR DLTD DLTW 1SO 7 . 73 1 .02 2 .47 4 . 24 0 . 58 1 . 16 4 . 59 0 .46 89 . 2 172 .8 102 . 4 250 . 1 1 1 . 25 0 . 26 10 . 3 10 .0 0 . 12 0 . 15 161 9 .90 -o .06 4 .35 5 .60 0 . 78 1 .04 6 .81 0 .45 94 .8 182 . 7 109 .2 266 . 1 16 .04 0 .27 10 . 3 10 .5 0 . 15 0 . 17 162 13 .94 1 .80 8 . 17 3 .97 2 .06 0 .58 8 .58 0 .45 98 . 7 196 .7 117 .8 287 .6 21 .48 0 . 27 14 .6 12 .9 0 . 25 0 . 11 163 14 . 70 1 . 76 3 .40 9 . 55 0 . 36 1 .32 9 . 1 1 0 .44 108 . 3 211 . 4 126 .9 311 .8 24 . 23 0. . 28 15 .0 12 . 1 0 . 14 0 . 22 164 5 .82 0 . 72 1 .57 3 . 53 0 .45 1 .29 3 .45- 0 .44 1 1 1 .8 217 . 2 130 .4 321 .0 9 . 20 0. . 26 9 .5 10 .0 0 .07 0 . 11 165 0 .06 0 .01 0 .03 0 .02 1 . 13 0 .86 0 .03 0 .44 1 1 1 .8 217 . 3 130 . 4 321 . 3 0 . 29 0 . 28 1 1 . 3 12 .9 0 . 18 0 . 15 166 10 .92 1 . 76 2 . 22 6 . 94 0 . 32 1 . 38 6 . 35 0 .44 1 18 .8 228 . 2 136 . 7 338 .9 17 .60 0. . 27 13 . 1 1 1 .6 0 . 1 1 0 . 15 167 6 .09 0 . 98 2 .02 3 .09 0 .65 1 .09 3 . 58 0 .44 121 .9 234 . 3 140 . 3 349 .4 10 . 46 0. .27 1 1 .0 1 1 .7 0 . 13 0 . 14 168 9 .81 1 . 57 1 .59 6 . 62 O . 24 1 . 35 6 . 16 0 .44 128 .5 244 . 1 146 . 5 362 .8 .13 .42 0. . 25 17 . 7 14 .9 0 . 22 0 . 28 170 1 1 . 18 1 . 33 2 .91 6 .95 0 .42 1 . 23 7 . 10 0 . 44 135 . 4 255 . 3 153 . 6 377 .5 14 . 74 0. . 25 12 . 2 12 .8 0 . 1 1 0. . 14 171 9 . 46 1 . 36 3 . 10 5 .00 0 .62 1 . 10 5 . 75 0 .43 140 . 4 264 . 7 159 . 3 392 . 4 14 .86 0. . 27 12 .0 12 .9 0 . 12 0 . 15 172 14 .08 1 .60 3 .85 8 .67 0, .44 1 . 24 8 .83 0. .43 149 . 1 278 .8 168 . 2 4 15 . 3 22 .96 0. . 26 14 . 2 13 .2 0. . 13 0 . 19 173 14 . 24 1 . 72 8 .61 3 .91 2 .20 0 .55 8 .91 0. . 43 153 .0 293 . 1 177 . 1 437 .5 22 . 17 0. 26 15 .5 12 .9 0. . 23 0 . 12 174 16 . 16 1 . 13 4 .86 10 . 17 0. . 48 1 . 27 10 . 13 0 . 39 163 . 2 309 . 2 187 . 2 462 .9 25 .43 0. , 28 13 . 3 12 .8 0. . 15 0. . 16 175 9 .41 0 .63 2 .85 5 . 73 0. .50 1 .20 6 .04 0 . 37 168 .9 318 .6 193 . 2 478 .4 15 . 52 0. . 30 12 . 1 1 1 . 7 0. .08 0. . 13 176 13 .21 1 .46 2 .78 8 .97 0 .31 1. .31 8 .63 0. . 33 177 .9 331 .8 201 . 9 498 .9 20 .43 0. 27 17 .0 12 .8 0. . 12 0. . 20 177 16 . 36 1 .61 2 .04 12 .71 0 . 16 1. .47 10 .90 0. .31 190 .6 348 . 2 212 .8 525. . 1 26 . 26 0. 27 19 . 4 13 .6 0. .07 0. . 22 178 12 .94 1 . 39 1 .69 9 .86 0. . 17 1. .45 8 .59 0. . 29 200 . 4 361 . 1 221 . 3 544 . 8 19 .71 0. 28 18 . 2 13 . 2 0. .04 0. . 18 179 14 . 34 1 .58 1 . 12 1 1 .64 0. . 10 1 . 54 9 . 52 0. .26 212 . 1 375 . 5 230 .9 567 .9 23. . 1 1 0. 27 20 . 1 13 .9 0. .02 0. 23 180 14 .83 1 .71 2 .01 1 1 . 1 1 0 . 18 1. . 39 10 .08 0. . 23 223 . 2 390 . 3 24 1 O 590 . 4 22 . 45 0. 27 20 . 1 14 .6 0. . 13 0 . 19 181 14 . 16 0 .91 4 .49 8 . 76 0. .51 1. . 17 9. .42 0. 23 231 .9 404 . 5 250. . 4 612 . 8 22 . 42 0. 27 14 . 2 15 . 1 0. . 16 0. .21 182 2 . 10 - 0 . . 78 1 . 23 1 .65 0. .75 1 . 12 1 .85 0. .30 233 .6 406 .6 252 . 2 616 . 1 3 . 28 0. 20 6 .4 10 .4 0. 03 0. .03 183 3, .88 0. .31 1 . 10 2 . 47 0. .44 1. .31 2. . 38 0. 38 236 . 1 410 . 4 254 . 6 622 . 5 6 . 45 0. 22 7 .9 9 .0 0. .04 0. .06 184 15 . 21 1. .66 4 .61 8 .94 0. .52 1. . 18 9 . 54 0. .46 245 .0 425. .6 264 . 1 647 . 0 24 . 48 0. 26 13 . 3 1 1 .7 0. 16 0. . 19 185 13 . 56 1. .95 2 .63 8 . 98 0. 29 1. . 30 8. .67 0. 48 254 .0 439. . 2 272 . 8 667 , .4 20 . 37 0. 25 16 .8 12 .0 0. 1 1 0. 22 186 15 . 82 2 . 13 2 .39 1 1 . . 29 0. 21 1. 28 1 1 . . 10 0. 47 265 . 3 455 . 0 283 . 9 689 , 7 22 . 35 0. 25 19 . 7 14 . 1 0. 1 1 0. 21 187 16 . 36 1 . . 76 2 .08 12 . 49 0. 17 1. 37 1 1 . .45 0. 46 277 .8 471 . 4 295 . 4 714 . 3 24 . 59 0. 26 20 . 2 15 . 0 0. 08 0. 20 188 5 . 72 0. 72 0 .36 4 . 63 0. 08 1. .56 3 . 75 0. 46 282 . 4 477 . 1 299 . 1 724 . 6 10. . 30 0. 25 15 . 4 13 . 2 0. 04 0. 06 189 13 . 07 1 . . 20 2 .50 9. . 37 0. 27 1. 32 8 . 97 0. 45 291 .8 490. .2 308 . 1 744 . 8 20. . 19 0. 27 17 . 3 14 . 1 0. 08 0. 18 190 16 . 44 2 . 01 2 .81 1 1 . .59 0. 24 1. 32 1 1 . .07 0. 44 303. .4 506 . 6 319. 2 768 . 6 23 . 83 0. 25 16 . 3 14 . 3 0. 1 1 0. 22 191 5. 48 0. ,71 0 ,47 4 . 30 0. 1 1 1. ,46 3. .71 0. 46 307 . 7 512. . 1 322 . 9 777 . 1 8. 47 0. 25 16 . 4 13 . 9 0. 02 0. 09 192 2 . 45 0. 19 0. .57 1 . 69 0. 34 1. 23 1 . 73 0. 47 309. .4 514. 5 324 . 6 780. 9 3. 76 0. 24 15 . 2 14 . 0 0. 07 0. 10 193 7 . 93 0. 24 1 . ,83 5 . 86 0. 31 1. 27 5 . 82 0. 48 315 . 2 522 . 5 330. 4 792 . 1 1 1 . 28 0. 24 14 . , 7 14 . 8 0. 10 0. 10 194 2 . 61 0. 02 0. . 39 2. 19 0. 18 1. 53 1 . 81 0. 49 317 . 4 525. 1 332 . 2 796 . 4 4 . 25 0. 23 10. .8 12 . 7 0. 04 0. 03 195 1 . 93 0. 45 0. . 19 1 . 28 0. 15 1. 26 1 . 28 0. 51 318. 7 527 . 0 333. 5 800. 0 3 . 60 0. 25 19 . 1 13 . 4 0. 0 0. 0 196 13 . 94 1 . 84 0. .63 1 1 . 47 0. 06 1. 34 10. 81 0. 49 330. . 2 540. 9 344 . 3 820. 8 20. 82 0. 24 21 . 7 14 . 3 0. 08 0. 16 197 15 . 58 2 . 01 1. .51 12 . 06 0. 12 1. 26 12. 06 0. 48 342 . 2 556 . 5 356 . 4 843 . 9 23 . 13 0. 24 21 .  3 15 . 1 0. 0 0. 0 198 13 . 42 2 . 30 1. 99 9. 13 0. 22 1. 22 9. 45 0. 47 351 . 4 570. 0 365 . 8 864. 7 20. 82 0. 24 23 . 8 16 . 1 0. 08 0. 17 199 14 . 85 2 . 06 1. 25 1 1 . 54 0. 1 1 1. 35 10. 74 0. 46 362 . 9 584 . 8 376 . 6 888 . 2 23 . 41 0. 24 25 . 0 16 . 9 0. 05 0. 18 201 15 . 23 1 . 79 4 . 31 9 . 14 0. 47 1. 05 10. 97 o. 43 372 . 0 600. 0 387 . 6 910. 7 22 . 57 0. 24 2 1 . 0 17 . 7 o. 15 0. 16 202 14 . 16 0. 93 4 . 07 9 . 16 0. 44 1. 15 10. 08 0. 42 381 . 2 614 . 2 397 . 6 933 . 2 22 . 43 0. 25 17. 8 17 . 5 0. 09 0. 08 203 10. 24 0. 55 3 . 19 6 . 51 0. 49 1. 18 6. 92 0. 43 387 . 7 624 . 4 404 . 6 949 . 3 16 . 12 0. 26 14 . 5 14 . 8 0. 10 0. 12 204 1 1 . 98 1. 05 2. 66 8 . 27 0. 32 1. 31 7 . 94 0. 43 396. 0 636 . 4 412. 5 966 . 3 16 . 99 0. 24 13 . 7 14 . 9 0. 07 0. 13 205 10. 31 1. 18 3 . 22 5 . 91 0. 54 1. 08 6 . 87 0. 43 401 . 9 646 . 7 419. 4 984 . 1 17 . 84 0. 24 15. 0 15 . 1 0. 1 1 0. 12 206 15. 02 1. 69 4 , 17 9 . 16 0. 46 1. 12 10. 26 0. 43 411. 0 661 . 7 429 . 6 1007 . 3 23 . 18 0. 25 16 . 9 14 . 9 0. 16 0. 21 207 14 . 04 1. 72 3. 06 9. 24 0. 33 1. 19 9. 74 0. 43 420. 3 675 . 8 439 . 4 1028 . 5 21 . 18 0. 24 19 . 2 15 . 1 0. 14 0. 23 tn u t o i o r o u u r o u F O F o i o u r o u F o u u r o r o u u r j u u u F O F O M F o o c u u u u Q Q U f o r o r o i o i o r o r o i o M i o ^ - L - . - . - . ^ - . - . ^ - L O O > 2 5 ) U l ^ U I O - ' O ( 0 C » > l l ! l U l J » U I O - ' O ( D a i > 1 0 ) 0 H ! . U I O - O I O 0 > < * O * O r O - > M O O - ' M - ' J - M M I O < J O ( J t J B U l l J ) > l U l l D O f O U - ' I I ) U t/l * - . v l u i O O U l - J O - J ^ l - ' l O ^ - ' I D - J I O O u l Q - J S I O I O U I O U O O > * 0 J l I 1 O O ( D O < > 0 ) O ( D < I ) ~ l - » O t J - J ^ ^ O M ^ - 4 O - J U O t O 0 1 XI * I o * 0 0 - ^ - » - * - ' 0 - ' - - - ' - ' 0 - » - ' - ' - ' - ' - ' 0 0 0 0 0 0 0 - ' - - 0 - ' N * m * o O M i o O O - ' O r o 6 U ( D i o - ' r o i J i u O ( ! ) U i - J f O f f l > ) 0 i ) u i o ~ j > i xi * c o w c j A o o ^ c j o o o i c o o i c r ) ( n c n 4 ^ t o c n c j u i - ' 0 ^ o o a i - - j f o - . ^ i . o * o * 0 - ' t o u w r o O u - ' M U O M U ^ u u j - - i o i o r o u u r o u - r o I * m * ^ O O C D C J o f e f e O C D C J l ^ C O O O C f l O C O O O ^ O t n c n U C f l N J t Q o - ^ C J t O & * f O < I l U l ( D ( 0 ^ - J ( I > m u > l ( D I D I O U 1 0 1 ( r ) ( J l l B ( J l t n C D I O O ^ O * I O M H * o * 0 0 - ~ ) O o c n - j - . o o o o - j ~ j o o o o ( O C D o o ~ j a i c o j ^ A ( j . ui co co co ~J C J co m * < * O i D ( l l t J 0 0 O - ' i o u n O - ' i o J i < n i j ) ( D i o > i u u i - i U i O t ~ ) i o ( » O > * C D ^ ^ C D C n N J C J f e C 0 0 3 f e r o c n M C J ( 0 C 0 C J C 0 c n O N J l 0 ( J C 0 C 0 t 0 ~ I C D "0 00 O - . M O O O O O O O O O O O O O O O O O O O O O O O O O O O o « co c o ^ a i c o - . A - ' C j N o c j ^ C D c ^ ^ N j o o o a c j c o c n ^ c j u i ^ u i - i . c o c n ^ z > ->• OO-^-^-^-^-^----^- — - — — — — - — r-"0 tO ~ J ( J I - i N 3 t O - ' - . | O I O - ^ O - ' - > - r o * ' - J - - ' M t O I O - . O - ' C 0 t O t O - - - . | O x O c o c n c n N J o t o ^ t n ^ ^ u o t o ^ f e ^ ^ c j c j c n c n c D C Q - ^ o t o c n c o c n > * -o * O ^ c o c o ^ ^ o c o c o o o o o c o o o c o ^ t o t o c n c j f e f e c j u i ^ c o t o o o f e c o * «> * - ' t o u i J ) - . 6 i o a ) u i c o ^ u ~ J o u i u i o u o ) i o ( D i i i c o - j ( D c n o - ' ^ * feCootntnONitOfeCDcjcj^cotjicn^fe^cnOfeoCJNocn-'-tsiio - i O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O S > CJ U U U U O < J U C O U C O U t t t > b b U O t O U U C O U C O C O t f c t > t H C J C J O — M c j c o ^ c n ^ o o c o o - ' M ^ o o o o o ^ o i c n c n c n ^ a J O - . c j c o m XI cn c D c n o D C D t n t n c n t n t n c n c n t n u i c n t n c n c n f e f e f e f e f e f e f e f e f e f e f e f e c/i O O O O O C 0 0 0 - - 4 - i cn u i u i ^ c o i o - ' - i . O c o a ) c D o o - j - ~ i c n o i u i 4 ^ c j i o c oo o o c o o j O N J c n o o ^ o o c o ^ ^ c n c D o a o ^ c o c n ^ O c i i w c n o o o o c j c o 2 O co C D ( D O ^ O - ' - ^ O O c n ^ o i c n c j o o i o c j c j - » c j O o i j i O o o o c j c j i t o ^ m co C D C o c o c o c o c D c o c o o 3 0 o c D o o o 3 C o c D O o ^ ^ ^ ^ ^ ^ ^ ^ ^ ~ j ~ j c n c n cn ui ui ui cn •&> C J io o c o o o ^ i c n ^ c j i o - . c o o o ~ j - j c n c ! i u i ^ c j - . o c o c D c - j ^ ^ ^ c j ^ ^ o o o c n u i c j ^ o o c n M ^ o o ^ c r ) - ^ c n ~ 4 - i - N 3 - ^ c o c r ) * . c » 2 O -4 ^ u i a i u u i o - j i D i o t o b i o i o m v i t s o n a i u O M t i d i u i u - ' O i i i * cn ODmOTcDOT icno i cnu i tncncntn t j i tnc^cncntn tn tn cn C J u u u r o - " ^ o o i o o i i - j o i o i u i J i Q t o ^ o o o i i ! a ! a ) > i - j ( i i u i t . c ~J - J v l U 1 > l ( » ^ A ( J { i U l ~ J I D I O O O U U M O U 1 - ( ! I I O I I l ( O O O U O J 2 T3 CO C D - J C O U 1 0 0 - J C J-i . - i C J l-iJ^-* CJCO£.COOO£>0~)CJ.bOOCO-itO-~JO">Ul H j i ^ c . ^ t t ( j u c o o c o c o u f o i o r o u ( o J . - - ^ - . - ^ - L O O O O cn ui c n a i c n c j ^ c o o o o o c n A N ) O C D O i ^ c j ^ c o o o - - j c n o i j ^ c j - ' C O - - j c n * . c fe. fefeON3fet0CJOMfeCncn^05C0WMCJNJfefelOfe--CJfeCJ--4C0 2 T: oo o o o i u i i o O M u - ' O - ' - J f c O m o i i i J i - ' i o c o f o i o i J i o - ' i o o o u i o a * ^. — - . - ^ - ^ - . - . - . f o — _» - L - ^ - . I O ^ . 7; * O c o ^ o o ^ c n c j o o ^ o o c o c o o o c o c n o c o o - J O - ' O o c j - j o o o c n c o c D o * o * C J t Q O T C 0 0 0 C 0 o o 0 3 f e N J f e f e U I f e o ( J C 0 ( 0 0 t J Q t n t 0 t 0 C J C J f e U l c * t o c j o ^ ^ o o c j ^ c n c j c D f e O c n f e t o f e ^ - ^ t n - ^ o c n o u i f e o o c o o o z O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O > oo to t O J t O t O U U - i l O I O t O U M I O r O I O I O I O t O U U M I O f O U f O U I O I J U a - J fetocjcjwcjCDuiucJOtnfefeCOfefeucoferoufeOTfeoicJGjfe o H - k - . _ . t O - ^ - . - ^ t O t O t O - . - - - k - . - . - ^ _ . - . - . - 4 . - i ^ - O cn c o o c o o o o o i c j o ^ o ^ ^ o o o 3 < f l C D c n c n t o M o U ) ^ c n c o o c D - - J O oo > O I 0 - ' - ' U ( I l O ^ - ' U ) ^ - > > l l > ) 0 1 I O - . U - > ^ ( I l ( ! l ( J 1 0 8 ! * i M I D XI - J . _ » - k - . _ » _ i . - i . _ . - i . _ . - . _ i . _ i . _ 4 . _ . _ . - » _ . _ . - » - . - . _ k _ » _ l . J . _ k _ » _ » _ l . (/) ro N J C j f e f e c j c j c j c n t n f e f e f e f e c n f e f e f e f e c j M c j f e f e f e c n t n u i u i u i oo > to - . ( o - . J i o i i . t . ^ ^ u ^ i j i t n t o a i - i o t o - . i D i J i O ' J i i o t o i i K r m xi O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O a - - 0 0 - ^ o - ' - - O O o - ^ o o o o O - ^ - ' 0 0 0 - ' 0 - ' O O o - ' 0 0 H O a ) c n ^ o M o f e t o - ' f o f e c j t o - ^ c o f e c j c o c n ~ j - . t o - - i . - j - ' t o c n o o o O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O o o O ^ - ' - ' - ' O - ' - ' - ' ^ - ' - ' ^ - ' U ^ - . O - ' - ' - ' - ' O O - ' - ' O M —I A c n f e c j c o ^ o t n o c j c n a i O T c o f O o O t n c j c n O f e o t n t o c D f e t J C o r o £ " .S-6 -_ 96 _ APPENDIX 2. L i s t i n g o f Growth-Water B a l a n c e Program. P R O G R A M L I S T I N G FOR G R O W T H AND W A T E R B A L A N C E INTEGER ICUT(5) REAL FC/2 15. / .WP/0. 15/,PEMAX/27./,ALPHA/1 .26/ ,TOT(5 ) /4*0. , 0 . 0 1 / , $GSLOPE/0.026/ , INTRCP/O. / , INF I LT /4 . / ,CUTGRO/0 .01 / C READ IN THE STARTING DATE, STORAGE(WATER), AND CUTTING DATES( ICUT(I )) READ (5,501) IDAY.WATER,( ICUT( I ) ,1=1,5) 1 = 1 C READ IN THE TEMPERATURE, RAINFALL, AND MODELLED NET RADIATION FOR THE DAY CHECK TO SEE THAT THE DAY IS LATER THAN THE SPECIFIED STARTING DATE AND C THAT THE SEASON IS NOT OVER (DAY=999). CHECK TO SEE IF CUTTING IS TODAY. 10 READ(5,500) NDAY,TBAR,PREC,OSTAR IF(NDAY.LT. IDAY) GO TO 10 IF(NDAY.EO.999 ) STOP IF (NDAY.NE. ICUT( I ) ) GO TO 20 CUTGRO=0.01 1 = 1 + 1 20 QG=0. 1*0STAR COMPUTE PRIESTLEY AND TAYLOR EVAPOTRANSPIRATION, AND ASSUME THE SOIL HEAT — C FLUX IS 10% OF THE NET RADIATION FLUX. SSG=0.432+0.0124*TBAR EVAP=0.4065*ALPHA*SSG*(QSTAR-QG) ETSOIL=EVAP-INTRCP 1 I F (ETSOIL .LT.O)ETSOIL=0 V£> SMAV=(WATER-WP*FC)/(FC*(1-WP)) - J COMPUTE SOIL LIMITED TRANSPIRATION AND CHECK TO SEE IF EMAX EXCEEDS THIS. PELIM=PEMAX*SMAV 1 IF (PELIM.LT.ETSOIL)ETSOIL=PELIM COMPUTE TRANSPIRATION BY THE TANNER AND JURY METHOD. FRAC=EXP(-3.*CUTGRO) ALFAS=ALPHA-((ALPHA-1. ) * ( 1 . - F R A C ) / ( 1 . - 0 . 3 5 ) ) TRANS=(1.-FRAC*ALFAS/ALPHA)*ETSOIL COMPUTE GROWTH FROM TRANSPIRATION, AND COMPUTE DRAINAGE AND INTERCEPTION GROWTH=TRANS*GSLOPE DRAIN=0. PREC=1 . 1*PREC INTRCP=0.55*PREC** (0 .53-0 .0085* (PREC-5 . ) ) PRECEF=PREC-INTRCP COMPUTE HORTON RUNOFF RUNOFF=0. DT = 2 IF(PRECEF.GT.10)DT=12. I F (PRECEF/DT .LT . INF ILT ) GO TO 30 RUNOFF = PRECEF-INF ILT*DT PRECEF=PRECEF-RUNOFF 30 CONTINUE COMPUTE THE WATER BALANCE WATER=WATER+PRECEF-ETSOIL-DRAIN IF(WATER.LT.FC ) GO TO 50 COMPUTE DUNNE RUNOFF AND ADD TO HORTON RUNOFF FOR DAY. RUNOFF=WATER-FC+RUNOFF WATER=FC 50 CONTINUE COMPUTE THE DAILY TOTALS, WRITE A LINE, AND GO TO THE NEXT DAY. TOT( 1 )=TOT(1) + ETSOIL T0T(2)=T0T(2)+PRECEF T0T(3)=T0T(3)+INTRCP TOT(4 ) =TOT(4)+RUN0FF T0T(5)=T0T(5)+GR0WTH CUTGRO=CUTGRO+GROWTH WRITE(6,600) NDAY,WATER,PRECEF,INTRCP,TRANS,EVAP,(TOT(I),1=1,5),GROWTH GO TO 10 500 F 0 R M A T ( I 3 , 2 X , 2 ( F 4 . 1 , 1 X ) , F 5 . 2 ) 501 F0RMAT( I 3 ,2X ,F3 .0 ,5 ( I 3 ,2X ) ) 600 F O R M A T ( I 3 , 2 X , 9 ( F 6 . 1 , 1 X ) , 2 X , 2 ( F 5 . 2 , 1 X ) ) END I CD I - 99 -APPENDIX 3. Output o f Growth-Water B a l a n c e Program. W A T E R B A L A N C E A N D G R O W T H F O R 1 9 7 8 ALL VALUES ARE IN MILLIMETRES, EXCEPT FOR THE GROWTH, WHICH IS IN TONNES/HA. THE COLUMN HEADINGS ARE DEFINED AS FOLLOWS: DAY: THE JULIAN CALENDAR DAY NUMBER WATER: THE WATER STORAGE IN THE ROOT ZONE PRECEF-.THE EFFECTIVE PRECIPITATION (PRECIP MINUS INTERCEPTION AND RUNOFF) INTRCP:THE AMOUNT OF PRECIPITATION INTERCEPTED BY THE FOLIAGE TRANSP:TRANSPI RATION CALCULATED BY TANNER AND JURY METHOD EVAPOT:EVAPOTRANSPIRATION(ETSOIL PLUS INTRCP FROM PREVIOUS DAY) TOTET: CUMULATIVE EVAP FOR THE SEASON TOTPCFCUMULATIVE PRECEF FOR THE SEASON TOTINT:CUMULATIVE INTRCP FOR THE SEASON TOTRNF:CUMULATIVE RUNOFF FOR THE SEASON TOTGRO:CUMULATIVE GROWTH FOR THE SEASON GROWTH:PREDICTED FORAGE GROWTH FOR THE DAY DAY WATER PRECEF INTRCP TRANSP EVAPOT TOTET TOTPCF TOTINT TOTRNF TOTGRO GROWTH 145 202 .9 0 .0 0 .0 0 . 1 2 . 1 2 . 1 0 .0 0 .0 0 .0 0 .01 0 .00 146 199 .6 0 .0 0 .0 0 . 2 3 .3 5 . 4 0 .0 0 .0 0 .0 0 .02 0 .00 147 197 .0 0 .0 0 . 3 0 . 2 2 . 7 8 .0 0 .0 0 . 3 0 .0 0 .02 0 .00 148 194 . 2 0 .0 0. .0 0 . 2 3 . 1 10 .8 0 .0 0 .3 0 .0 0 .03 0 .01 149 192 .6 0 .0 0 .0 0 . 2 1 .6 12 .4 0 .0 0. .3 0 .0 0. .03 0 .00 150 189 .3 0 .0 0. .0 0 .4 3 .3 15 . 7 0 .0 0. .3 0 .0 0. .04 0 .01 151 185 .6 0 .0 0. .0 0 .5 3 . 7 19 .4 0 .0 0 . 3 0 .0 0. .05 0. .01 152 181 .5 0 .0 0. .0 0 .8 4 . 1 23 .5 0 .0 0. . 3 0 .0 0 .07 0. .02 153 177 . 2 0 .0 0. .0 1 . 1 4 .4 27. .9 0 .0 0. . 3 0 .0 0. . 10 0. .03 154 172 .9 0 .0 0. .0 1. .4 4 . 3 32 . 2 0 .0 0. . 3 0 .0 0. . 14 0. .04 155 168 . 5 0 .0 0. .0 1. .8 4 . 3 36. . 5 0 .0 0. . 3 0 .0 0. 18 0. .05 156 166 .9 0 .0 0. 0 0. .8 1 .6 38 . 1 0 .0 0. . 3 0 .0 0. .20 0. .02 157 163 .4 0. .0 0. 0 1. .9 3 .6 4 1 . . 7 0 .0 0. 3 0 .0 0. . 25 0. .05 158 159 . 1 0 .0 0. .0 2 . 6 4 . 2 45 . 9 0. .0 0. .3 0 .0 0. 32 0. .07 159 155 .8 0. .0 0. 0 2 . 3 3 . 4 49. 3 0. .0 0. 3 0 .0 0. 38 0. 06 160 153 .5 0. . 8 0. 7 2 . 3 3 . 1 52 . 3 0. .9 1. 0 0. .0 0. 44 0. .06 161. 152 . ,6 0. .0 0. 3 0. 8 1 .7 53 . 3 0. .9 1. 3 0 .0 0. 46 0. 02 162 150. .4 0. .0 0. 0 1 . 7 2, .4 55. 5 0. .9 1. 3 0. .0 0. 51 0. 04 163 149. . 1 2 . 2 1. 0 2 . 9 3 . 5 59. 0 3 . 1 2 . 3 0. .0 0. 58 0. 08 164 147 . 9 0. .4 0. 5 1 . 4 2 . 6 60. 6 3 . 4 2 . 8 0. .0 0. 62 0. 04 165 145 . ,9 0. .5 0. 6 2 . 2 3. .0 63. 0 4 . 0 3 . 4 0. .0 0. 68 0. 06 166 142 . 6 0. 0 0. 0 3 . 1 4 . 0 66. 4 4 . 0 3. 4 0. .0 0. 76 0. 08 167 138 . 9 0. .0 0. 0 3 . 3 3 . ,6 70. 0 4. 0 3 . 4 0. ,0 0. 84 0. 09 168 141 . 8 5 . 5 1. 5 2 . 6 2 . 7 72 . 7 9. 5 4 . 9 0. .0 0. 91 0. 07 169 140. .6 0. 0 0. 0 1 . 1 2 . 7 73. 9 9. 5 4 . 9 0. .0 0. 94 0. 03 170 137 . 1 0. 0 0. 0 3. 4 3. .5 77 . 4 9. 5 4 . 9 0. 0 1. 03 0. 09 171 133 . 5 0. 2 0. 4 3. 7 3. 8 81 . 2 9. 7 5. 3 0. 0 1. 12 0. 10 DAY WATER PRECEF INTRCP TRANSP EVAPOT TOTET TOTPCF TOTINT TOTRNF TOTGRO GROWTH 172 136 . 5 3 . 9 1 .3 0 .8 1 . 2 82 .0 13 .5 6 .6 0 .0 1 . 14 0 .02 173 135 . 1 0 .0 0 .0 1 .4 2 . 7 83 .4 13 .5 6 .6' 0 .0 1 . 18 0 .04 174 131 .6 0 .0 0 .0 3 .4 3 . 5 86 .9 13 . 5 6 .6 0 .0 1 . 27 0 .09 175 127 .4 0 .0 0 .0 4 . 1 4 . 2 91 . 2 13 .5 6 .6 0 .0 1 . 37 0 . 11 176 123 . 2 0 .0 0 .0 4 . 1 4 . 1 95 . 3 13 .5 6 .6 0 .0 1 . 48 0 . 11 177 1 18 .9 0 .0 0 .0 4 .3 4 . 3 99 .6 13 .5 6 .6 0 .0 1 . 59 0 . 11 178 1 14 .6 0 .0 o .0 4 . 3 4 . 3 103 .9 13 .5 6 . 6 0 .0 1 . 70 0 . 11 179 1 10 . 1 0 .0 0 .0 • 4 .4 4 .4 108 . 4 13 .5 6 .6 0 .0 1 .82 0 . 12 180 105 .9 0 .0 0 .0 4 . 2 4 . 2 1 12 .6 13 .5 6 .6 0 .0 1 . 93 0 . 11 181 103 .5 0 .0 0 .0 2 .4 2 .5 115 . 1 13 .5 6 .6 0 .0 1 .99 0 .06 182 99 . 4 0 .0 0 .0 4 .0 4 .0 119 . 1 13 .5 6 .6 0 .0 2 . 10 0 . 10 183 95 .0 0 .0 0 .0 4 .4 4 .4 123 .5 13 .5 6 .6 0 .0 2 .21 0 . 11 184 90 .7 0 .0 0 .0 4 .3 4 .4 127 .9 13 .5 6 .6 0 .0 2 . 32 0 . 11 185 86 .8 0 .0 0 .0 3 .8 3 .9 131 .7 13 .5 6 .6 0 .0 2 . 42 0 . 10 186 89 .8 5 . 7 1. . 5 2 .8 2 .8 134 .5 19 . 3 8 . 1 0 .0 2 . 50 0 .07 187 90 . 3 0 . 5 0 .6 -0 .O 1 .4 134 .5 19 . 8 8 . 7 0 .0 2 . 50 0 .0 188 88 .8 0 .0 0 .0 1 . 5 2 . 1 136 .0 19 .8 8 . 7 0. .0 2 . 54 0 .04 189 85 . 4 0 .0 0 .0 3 .4 3 . 4 139 .3 19 .8 8 . 7 0 .0 2 .62 0 .09 190 83 . 7 0 . 1 0. . 3 1 .8 1 .8 141 .2 19 .9 9 .0 0. o 2 . 67 o .05 191 87 .9 4 .9 1. .4 0 .8 1 . 1 141 .9 24 .8 10 .5 0 .0 2 . 69 0 .02 192 85 .0 0 .0 0. .0 2 .9 4 . 3 144. .8 24 .8 10 .5 0. .0 2 . 77 0 .08 193 82 . 3 0 .0 0. .0 2 . 7 2 . 7 147 . 5 24 .8 10 . 5 0. .0 2 .84 0 .07 194 78 .9 0 .0 0. .0 3 .4 3 .4 150 .9 24 .8 10 . 5 0. .0 2 . 92 0 .09 195 74 .4 0 .0 0. .0 4 .5 4 .5 155 . 4' 24 .8 10. . 5 0. .0 3 .04 0 . 12 196 70 .5 0 .0 0. .0 3 .9 3 .9 159. . 3 24 .8 10. . 5 0. .0 3 . 14 0. . 10 197 67 . 4 -0. .0 0. 2 3 . 1 3 . 1 162 . 5 24 .8 10. . 7 0. .0 3 . 22 0. .08 198 64 . 6 0. .0 0. 0 2 .7 2 .9 165 . 2 24 .8 10. . 7 0. .0 3 . 29 0. .07 199 62 . 3 0. .0 0. 0 2 .3 2 . 3 167 . 5 24 . 8 10. . 7 0. 0 3 . 36 0. .06 200 60 .0 1. . 3 0. 9 3 . 7 3 . 7 171 . , 2 26 . 2 11. .6 0. 0 3 .45 0. . 10 201 57 . 4 0. .0 0. 0 2 .6 3. .4 173 . 8 26 . 2 11. .6 0. o 3 . 52 0. 07 202 53 . 7 0. .0 0. 0 3. . 7 4 . 4 177 . 5 26 . 2 11. .6 0. 0 3 .62 0. . 10' 203 50. . 5 0. .0 0. 0 3 . . 2 4 . . 3 180. . 7 26 . 2 11. 6 0. 0 3 . 70 0. .08 204 47 . 8 0. 0 0. 0 2 . . 7 3, , 3 183. 4 26 . 2 11. 6 0. 0 3. . 77 0. 07 205 45 . 5 0. .0 0. 0 2 . . 3 3 . 1 185 . 7 26 . 2 11. 6 0. 0 3 .83 0. 06 206 43 . 5 0. .0 0. 0 2 . 0 4 . . 3 187 . 6 26 . 2 11. 6 0. 0 3 . 88 0. 05 207 59. .2 17 . 3 1. 8 1 . .7 4 . 0 189. 3 43. 5 13. 4 0. 0 3 .92 0. 04 208 60. .4 1. 3 0. 8 -0. .0 1 . .6 189. 3 44 . 7 14 . 2 0. 0 3. .92 0. 0 209 58 . 1 0. 0 0. 0 2 , .3 3 . . 2 191 . 6 44 . 7 14 . 2 0. 0 3. .98 0. 06 210 56 . ,7 1. 5 0. 9 2 . 9 2 . 9 194 . 5 46 . 2 15. 1 0. 0 4 . 06 0. 07 21 1 53 . 9 -0. 0 0. 2 2 . 8 3 . 7 197 . 3 46. 2 15. 4 0. 0 4 . 13 0. 07 212 52 . 2 1. 4 0. 9 3 . 2 3 . 6 200. 5 47 . 7 16. 2 0. 0 4 . 21 0. 08 213 49 . 8 -0. 0 0. 2 2 . 4 3 . 2 202 . 9 47 . 7 16 . 5 0. 0 4 . 27 0. 06 214 47 . 2 0. 0 0. 0 2. 6 3 . 7 205 . 4 47 . 7 16 . 5 0. 0 4 . . 34 0. 07 215 45 . 0 0. 0 0. 0 2 . 2 4 . 0 207 . 7 47 . 7 16 . 5 0. 0 4 . 40 0. 06 216 50. 9 7 . 8 1. 7 1 . 9 3. 6 209 . 5 55 . 5 18 . 1 0. 0 4 . 45 0. 05 217 49 . 0 0. 0 0. 0 1 . 9 3 . 6 211. 5 55. 5 18 . 1 0. 0 4 . 50 0. 05 218 47 . 1 o. 0 0. 0 1 . 9 1 . 9 213. 3 55. 5 18 . 1 0. 0 4 . 55 0. 05 DAY WATER PRECEF INTRCP TRANSP EVAPOT TOTET TOTPCF TOTINT TOTRNF TOTGRO GROWTH 219 44 .9 0 .0 0 .0 2 . 2 3 .2 215 . 5 55 . 5 18 . 1 0 .0 4 .60 0 .06 220 43 .0 0 .0 0 .0 1 .9 4 .0 217 .4 55 . 5 18 . 1 0 .0 4 .65 0 .05 221 41 .5 0 .0 0 .0 1 .6 3 . 7 219 .0 55 .5 18 . 1 0 .0 4 . 69 0 .04 222 40 . 1 0 .0 0 .0 1 . 4 2 .3 220 .4 55 . 5 18 . 1 0 .0 4 .73 0 .04 223 39 .7 0 . 8 0 .7 1 . 2 1 .4 221 . 5 56 . 2 18 .8 0 .0 4 .76 0 .03 224 41 .6 2 . 1 1 .0 0 . 1 0 .8 221 .6 58 . 3 19 .8 0 .0 4 . 76 0. .00 225 40 .3 0 .0 0 .0 1 . 4 2 .8 223 .0 58 . 3 19 .8 0 .0 4 .80 0. .04 226 39 . 1 0 .0 0 .0 1 . 2 3 . 2 224 . 2 58. .3 19 . 8 0 .0 4 .83 0. .03 227 60 .6 22 .5 1 .8 1 .0 1 .7 225 . 2 80 .8 21 .6 0 .0 4 .86 0. .03 228 63 . 4 2 .8 1 . 2 -0 .0 1 .0 225 . 2 83. .6 22. . 7 0 o 4 .86 0. .0 229 63 . 2 0 .9 0 . 7 1. . 1 2 .2 226 . 3 84 . 5 23. . 5 0 .0 4 .88 0. .03 230 65 .6 2 . 9 1 . 2 0 .5 1 . .3 226 .8 87 . 4 24 . 6 0 .0 4 .90 0. .01 231 65 .6 - 0 . .0 0 . 2 - 0 .0 0 .9 226 .8 87 .4 24. .9 0 .0 4 .90 0. .0 232 63 .3 0. .0 0 .0 2. . 3 2 .6 229 .2 87 . 4 24 . 9 0. .0 4 .96 0. .06 233 61 . 1 0. .0 o. .0 2 . 1 2 . 1 231 .3 87. .4 24 . 9 o. .0 5 . 01 0. 06 234 59 .5 1. . 3 0. . 8 2 . 9 2 . 9 234. .2 88 . 7 25 . 7 0. .0 5 , .09 0. 07 235 69 .8 10. .6 1. .8 0 .4 1 . . 2 234 . 6 99. . 3 27 . 5 0. .0 5 . 10 0. 01 236 70 .4 0. . 7 0. .6 - 0 . .0 1 . . 7 234 .6 100, 0 28 . 1 0. .0 5 . 10 0. 0 237 69 .9 0. . 2 0. . 4 0. . 7 1 . .4 235. .3 100. .2 28 . 5 0. .0 5 . 12 0. 02 238 69. . 7 1. .6 0. .9 1 . 8 2 . 2 237 . 1 101 . 8 29. 4 0. 0 5 . , 17 0. 05 239 67 , . 7 0. .0 0. .0 2 . 0 2. .9 239. . 1 101 . 8 29. 4 0. .0 5 . 22 0. 05 240 64 . 7 0. 0 0. ,0 3. .0 3. .0 242 , . 1 101 . 8 29. 4 0. 0 5 , .29 0. 08 241 61 . 8 0. 0 0. 0 2 . 9 2 . 9 245 . 0 101 . 8 29. 4 0. 0 5 . 37 0. 08 242 58 . 9 0. 0 0. 0 2 . 8 2 . 8 247 , .8 101 . 8 29. 4 0. 0 5 . 44 0. 07 243 58. .5 1. 3 0. 9 1 . 8 1 . 8 249 . 6 103. 1 30. 3 0. 0 5. .49 0. 05 - 103 -APPENDIX 4. Measured and M o d e l l e d Net R a d i a t i o n Data f o r 1978 and 19 1 9 7 8 N E T R A D I A T I O N E S T I M A T E S THE COLUMN HEADINGS BELOW ARE DEFINED AS FOLLOWS: DAY: THE JULIAN CALENDAR DAY NUMBER OSTAR: THE MEASURED VALUE OF NET RADIATION FLUX DENSITY EST 1: THE ESTIMATE OF OSTAR AS EXPLAINED BELOW ERR 1: QSTAR-EST1 ERSUM: THE CUMULATIVE SUM OF ERR 1 OVER ALL DAYS ESTIMATES ARE: 1.IDSO-JACKSON USING 24HR MEAN TEMP 2.IDSO-JACKSON USING DAYTIME MEAN (FROM EB OR 3TMAX+TMIN/4) 3. REGRESSION FROM KDOWN(SP) CALCULATED FROM KDOWN(FSJ) 4. REGRESSION DIRECTLY FROM KDOWN(FSJ) DAY OSTAR EST 1 ERR 1 ERSUM EST2 ERR2 ERSUM EST3 ERR3 ERSUM EST4 ERR4 ERSUM 121 MISSED 9 .94 9 .87 1 1 . 22 10 . 40 122 MISSED 12 .21 1 1 .97 13 .53 12 . 34 123 MISSED 12 .91 12 .47 14 .05 12 . 78 124 MISSED 13 . 14 12 .54 14 .09 12 .82 125 MISSED 13 .05 12 .59 14 . 13 12 .85 126 MISSED 10 . 17 9 .93 1 1 . 16 10 . 35 127 MISSED 13 . 18 13 .04 14 . 56 13 .21 128 MISSED 1 1 • ?8 1 1 .32 12 .63 1 1 , .59129 MISSED 8 .84 8 .59 9 .62 9 .05 130 MISSED 6 .97 6 .47 7 . 29 7 , .09 131 MISSED 10 . 20 9 .93 1 1 .05 10, .25 132 MISSED 13 .44 13 . 33 14 . 73 13 , . 35 133 MISSED 9 .05 8 .83 9 .81 9 . 2 1 134 MISSED 6 .99 6 .93 7. . 74 7 . 46 135 MISSED 1 . .64 1 .47 1 . .83 2 . 48 136 MISSED 12 .85 12 . 77 14 . 01 12 . 75 137 MISSED 9. . 54 9 .53 10. . 50 9 . 79 138 MISSED 13. , 19 13 . 13 14 . 36 13 .04 139 MISSED 10. . 57 10 .64 1 1 . ,65 10. . 76 140 MISSED 5. . 16 5 . 18 5 . 79 5 . 82 141 MISSED 4 . 00 3 , .94 4 . ,45 4 . 69 142 MISSED 4 . 19 3 . .87 4 . 37 4 . ,63 143 MISSED 8 . 39 7 . 98 8 . , 74 8 . ,31 144 MISSED 12 . 54 12 . 26 13 . 29 12 . , 14 145 MISSED 8 . 29 8 . 27 9 . ,03 8 . 55 146 MISSED 12. .93 13 .00 14 . ,03 12 . 77 147 MISSED 10. .56 10. . 58 1 1 . .45 10. 59 148 MISSED 13 . 22 13 . 13 14 . , 13 12 . 85 149 MISSED 6 . 96 6 . 79 7 . 42 7 . 19 150 MISSED 13 . 82 13 . 77 14 . , 76 13 . 38 DAY OSTAR EST 1 ERR 1 ERSUM EST2 ERR2 ERSUM EST3 ERR3 ERSUM EST4 ERR4 ERSUM 151 MISSED 14 .88 14 .96 15 .99 14 .42 152 MISSED 15 . 36 15 .49 16 .53 14 .87 153 MISSED 15 .64 15 . 75 16 . 78 15 .08 154 MISSED 15 .01 15 .09 16 .06 14 .47 155 MISSED 15 .21 15 .30 16 . 26 14 .64 156 MISSED 5 .84 5 .87 6 . 38 6 . 32 157 MISSED 14 . 53 14 . 56 15 .44 13 .95 158 13.07 16 .00 -2 .93 -2 .93 16 . 13 -3 .06 -3 .06 17 .06 -3 .99 -3 .99 15 . 32 -2 . 25 -2 . 25 159 13.43 12 . 77 0 .66 -2 .28 12 .91 0 .52 -2 .55 13 .65 -0-, . 22 -4 .21 12 .45 0 .98 - 1 . 27 160 10. 20 12 . 75 -2 . 55 -4 .82 12 .80 -2 .60 -5 . 15 13 .47 -3 . 27 -7 . 48 12 . 29 -2 .09 -3 . 36 161 MISSED 7 .06 6 .93 7 .49 7 . 25 162 MISSED 10 .02 9 .92 10 . 59 9 .87 163 MISSED 14 .42 14 . 36 15 . 19 13 . 74 164 MISSED 10 . 32 10 . 29 10 .95 10 . 17 165 MISSED 1 1 . 34 1 1 . 35 12 .03 1 1 .08 166 MISSED 15 .06 15 . 10 15 .90 14 . 34 167 MISSED 13 .89 13. .92 14 .66 13 . 30 168 MISSED 10 . 34 10. . 35 10 .96 10 . 17 169 MISSED 1 1 .31 1 1 . 16 1 1 .77 10 . 86 170 MISSED 13. . 95 13. .94 14 .62 13 . 26 171 MISSED 14 , . 59 14 . ,61 15 . 30 13 .84 172 MISSED 4 . 60 4 . 56 4 .94 5 . 1 1 173 MISSED 10. . 77 10. . 74 1 1 . 28 10 .45 174 1 1 . 30 14 . 03 -2 . 73 -7 . 55 14 . 01 -2 . .71 -7 .86 14 .62 -3 . 32 - 10 .81 13 . 26 - 1 . .96 -5 . 32 175 MISSED 15 . 47 15 . 47 16 . 15 14 , 55 176 14 . 70 15. .44 - 0 . . 74 -8 .29 15. 45 - 0 . 75 -8 .60 16 . 10 - 1 . 40 -12. .21 14 . 51 0. 19 -5 . 13 177 15.98 16 . 14 - 0 . . 16 -8 . 45 16. . 14 - 0 . 16 -8 .76 16 . 79 - 0 . 81 -13 .02 15 . ,09 0. 89 -4 . .25 178 15.42 16 . 35 - 0 . .93 - 9 . .38 16. . 34 - 0 . 92 - 9 . ,68 16. .98 - 1 . 56 -14 .59 15 . 25 0. 17 -4 .08 179 16. 17 16 . 40 - 0 . .23 - 9 . .61 16. 41 - 0 . 24 - 9 . .92 17 . 02 - 0 . 85 -15 . . 44 15 . , 29 0. 88 - 3 . . 20 180 13.60 15 . 14 - 1 . .54 -11 . . 15 15. 13 - 1 . 53 -11 . ,45 15. . 70 -2 . 10 - 17 . , 54 14 . 17 - 0 . 57 -3 . 76 181 10. 15 8 . 62 1 . .53 -9 . 62 8 . 62 1. 53 -9 . 92 9. .04 1 . 1 1 -16. .43 8 . 56 1. 59 -2 . . 18 182 15 . 25 16. 12 - 0 . 87 -10. .48 16. 05 - 0 . 80 -10. 72 16 . 61 -1 . 36 - 17 . 78 14 . 93 0. 32 -1 . 86 183 16 . 16 16. 19 - 0 . 03 - 10. .51 16 . 19 - 0 . 03 -10, . 75 16 . 72 -o. 56 -18. 35 15 . 03 1. 13 - 0 . .74 184 15.83 15. 58 0. 25 - 10. 26 15. 58 0. 25 -10. 49 16. .07 - 0 . 24 -18 . 58 14 . 48 1. 35 0. 61 185 16 .03 13 . 81 2 . 22 -8 . 04 13. 82 2 . 21 - 8 . .29 14 . 26 1 . 77 -16 . 81 12 . 95 3 . 08 3 . 69 186 MISSED 9. 65 9. 65 10. 02 9 . 39 187 MISSED 5 . 30 5. 24 5. 55 5 . 62 188 MISSED 7 . 97 7 . 92 8 . 25 7 . 90 189 MISSED 13 . 69 13 . 61 13 . 99 12 . 73 190 MISSED 6 . 78 6 . 77 7 . 07 6 . 90 191 MISSED 3 . 78 3. 77 4 . 04 4 . 35 192 MISSED 15 . 53 15. 53 15 . 88 14 . 32 193 MISSED 9. 29 9. 29 9. 58 9 . 01 194 MISSED 1 1 . 95 1 1 . 95 12 . 24 1 1 . 26195 MISSED 16 . 47 16 . 48 16 . 78 15 . 08 196 MISSED 13 . 76 13 . 76 14 . 03 12 . 76 197 MISSED 1 1 . 44 1 1 . 45 1 1 . 70 10. 80 DAY OSTAR EST 1 ERR 1 ERSUM EST2 ERR2 ERSUM EST3 ERR3 ERSUM EST4 ERR4 ERSUM 198 MISSED 1 1 .25 1 1 . 24 1 1 .48 10. .62 199 MISSED 8 .93 8 .90 9 . 13 8 . 63 200 13 . 50 14 . 18 -0 .68 -8 , . 72 14 . 18 -0 . .68 -8 .97 14 . 40 -0 .90 - 17 . 71 13 . 07 0. 43 4 . 1 1 201 10.08 12 . 29 -2 .21 -10, .93 12 . 28 -2 . . 20 -11 . 17 12 .49 -2 .41 -20 . 12 1 1 . .47 -1 . 39 2 . 72 202 13.86 15 . 25 -1 .39 -12, . 32 15 . 23 -1 . 37 -12 .54 15 . 39 -1 . 53 -21 . .65 13 . 91 - 0 . 05 2 .67 203 12 .07 14 .81 -2 . 74 -15 . .06 14 . 76 -2 . 69 -15 . 23 14 .92 -2 .85 -24 , . 50 13 . 51 - 1 . 44 1 . 23 204 10.05 1 1 . 37 -1 .32 -16, . 37 1 1 . 35 -1 . 30 - 16 .53 1 1 .51 - 1 . . 46 -25 , .96 10. .65 - 0 . 60 0 .64 205 9 . 74 10 .67 - 0 . .93 -17 . 30 10 .64 -0 . .90 -17 . 43 10 .80 -1 . 06 -27 , .02 10. .05 - 0 . 31 0 . 33 206 13.51 15 .04 -1 .53 -18. .83 15 .02 -1 . 51 -18 . 94 15 . 14 -1 . 63 -28 .66 13 . 70 - 0 . 19 0 . 14 207 12.16 13 .80 -1 . 64 -20. .47 13 . 77 - 1 . .61 -20 . 55 13 .88 -1 . 72 -30, . 38 12 . 64 - 0 . 48 -0 .34 208 5 . 75 5 . 22 0 .53 -19 . .94 5 . 22 0. . 53 -20 .02 5 . 39 0, . 36 -30, .02 5 . 49 0. 26 -0 .08 209 1 1 .68 1 1 . 74 - 0 .06 -19 . 99 1 1 . 74 -0 . .06 -20 .07 1 1 . 86 -0 . 18 -30, . 20 10. .94 0. 74 0 .66 210 13.04 10 . 37 2 .67 - 17 . 32 10 . 38 2 . 66 -17 .42 10 . 50 2 , . 54 -27 , .66 9 . 79 3. 25 3 .92 21 1 12 .85 13 .89 -1 .04 -18. . 36 13 .89 -1 . 04 -18 .46 13 .97 -1 , . 12 -28 . 78 12 . 72 0. 13 4 .05 212 1 1 .55 13 .47 -1 . 92 -20. . 29 13 .48 -1 . 93 -20 . 39 13 . 55 -2 , .00 -30, . 78 12 . 36 - 0 . 81 3 . 23 213 12 .05 13 . 32 -1 . 27 -21 . .56 13 .21 -1 . 16 -21 . 55 13 . 28 -1 , . 23 -32 . .02 12 . 14 - 0 . 09 3 . 15 214 MISSED 15 . 39 15 . 27 15 . 32 13 . 85 215 MISSED 14 .72 14 . 73 14 . 77 13 . 39 216 MISSED 12 . 39 12 . 33 12 . 39 1 1 . 38217 MISSED 13 .80 13 . 78 13 .82 12 . 59 218 MISSED 6 .81 6 .80 6 .90 6 . 76 219 MISSED 1 1 .90 1 1 .90 1 1 .94 1 1 . .00220 MISSED 13 .95 13 .92 13 .93 12 . 68 221 MISSED 12 .85 12 .81 12 .83 1 1 . . 76 222 6.15 8 .04 - 1 . .89 -23 . .46 8 .05 -1 . 90 -23 . 45 8 . 12 -1 , .97 -33 . 99 7 . 79 - 1 . 64 1 .51 223 5 . 56 5 .21 0. . 35 -23 . 10 5 . 13 0. .43 -23 .02 5 . 24 0, . 32 -33 . 66 5 . 36 0. 20 1 .72 224 1 .87 2 . 79 - 0 . ,92 -24 . 02 2 .71 - 0 . .84 -23, .86 2 .83 - 0 . .96 -34 . .63 3. , 33 -1 . 46 0 . 26 225 11.41 1 1 •,51 - 0 . . 10 -24 . . 13 1 1 .42 -0 . .01 -23, .86 1 1 .43 - 0 , .02 -34 . .65 10. .57 0. 84 1 .09 226 8.30 12 .02 - 3 . ,72 -27 . .85 12 .01 - 3 . .71 -27 , . 57 12 .03 -3 , . 73 -38 . 37 1 1 . ,08 -2 . 78 -1 .69 227 5.13 6 . 75 - 1 . ,62 -29 . .47 6 .68 -1 . 55 -29, . 12 6 . 75 - 1 . .62 -39 . 99 6 . ,63 -1 . 50 -3 . 19 228 MISSED 4 .06 4 . 35 4 .04 4 , 35 229 MISSED 8 .55 9 . 27 8 . 57 8 , 17 230 MISSED 4 .95 5 .31 4 .92 5 . ,09 231 MISSED 3 .79 3 .96 3 .67 4 . 04 232 MISSED 1 1 . . 32 1 1 .97 1 1 .06 10. . 26 233 MISSED 8. .50 9. . 16 8 .47 8 . ,08 234 MISSED 1 1 .96 12 .81 1 1 .84 10. .92 235 MISSED 4 .40 4 .81 4 .45 4 . , 70 236 MISSED 6 .40 6 .98 6 .45 6 . 38 237 MISSED 4 .92 5 . 39 4 .98 5 . , 14 238 MISSED 8 . 72 9 .42 8 . 70 8 . , 28 239 MISSED 1 1 . 16 12 . 12 1 1 . 20 10. 38 240 MISSED 1 1 .53 12 .49 1 1 . 55 10, .67 241 MISSED 1 1 .48 12 .45 1 1 .51 10. .64 242 MISSED 10. .58 1 1 .51 10 .65 9 . 92 243 MISSED 6 .67 7 , . 27 6 . 73 6 . 61 VARIANCE OF ESTIMATE 1=2.710 VARIANCE OF ESTIMATE2=2.690 VARIANCE OF ESTIMATE3=3.392 VARIANCE OF ESTIMATE4=1.873 1 9 7 9 N E T R A D I A T I O N E S T I M A T E S THE COLUMN HEADINGS BELOW ARE DEFINED AS FOLLOWS: DAY: THE JULIAN CALENDAR DAY NUMBER QSTAR: THE MEASURED VALUE OF NET RADIATION FLUX DENSITY EST 1: THE ESTIMATE OF OSTAR AS EXPLAINED BELOW ERR 1 : QSTAR-EST1 ERSUM: THE CUMULATIVE SUM OF ERR 1 OVER ALL DAYS ESTIMATES ARE: 1.IDSO-JACKSON USING 24HR MEAN TEMP 2.IDSO-JACKSON USING DAYTIME MEAN (FROM EB OR 3TMAX+TMIN/4) ' 3. REGRESSION FROM KDOWN(SP) CALCULATED FROM KDOWN(FSJ) 4. REGRESSION DIRECTLY FROM KDOWN(FSJ) DAY OSTAR EST 1 ERR 1 ERSUM EST2 ERR2 ERSUM EST3 ERR3 ERSUM EST4 ERR4 ERSUM 139 6 . 8 4 8 . 3 0 - 1 . 4 6 - 1 . . 46 8 . 29 - 1 . .45 - 1 . . 45 9 . 0 5 - 2 . 21 - 2 . 2 1 9 . 0 9 - 2 . . 25 - 2 . . 25 140 3 . 13 6 . 8 8 - 3 . 7 5 - 5 . . 2 1 6 . . 84 - 3 . . 7 1 - 5 . 16 7 . 48 - 4 . . 35 - 6 . 57 7 . 6 0 - 4 . . 47 - 6 . 72 14 1 6 . 17 10. . 5 3 - 4 . 36 - 9 . . 58 10. . 53 - 4 . . 36 - 9 . . 52 1 1 . 4 1 - 5 . . 24 - 1 1 . 8 0 1 1 . 32 - 5 . . 15 - 1 1 . . 87 142 1 1 . 8 8 13 . 0 6 - 1 . 18 - 10 . . 76 13 .05 - 1 . . 17 - 1 0 . . 7 0 13 . 8 1 - 1 . .93 - 1 3 . 73 13 . 6 0 - 1 . . 72 - 1 3 . . 59 143 7 . 6 2 7 . 28 0 . 3 4 - 10 . . 4 1 7. . 3 1 0 . . 3 1 - 10. . 38 7 . 9 2 - 0 . . 30 - 1 4 . 0 3 8 . 0 2 - 0 . . 4 0 - 13 .98 144 1 1 . 45 1 1 . . 15 0 . 3 0 - 10. . 12 1 1 . . 14 0 . . 3 1 - 10, ,07 1 1 . 9 8 - 0 . . 53 - 14 . 56 1 1 . 8 6 - 0 . . 4 1 - 14 . 39 145 1 1 . 8 9 10. . 9 4 0 . 9 5 - 9 . . 17 10. . 97 0 . . 92 - 9 . . 15 1 1 . 76 0 . . 13 - 1 4 . . 4 3 1 1 . 6 5 0 . . 24 - 1 4 . . 15 146 6 . 6 1 5 . . 35 1 . 26 - 7 . . 9 1 5 . . 36 1 . . 25 - 7 . . 8 9 5 . 9 0 0 . . 7 1 - 1 3 . . 7 2 6 . 10 0 . . 5 1 - 13 .65 147 2 . 7 1 2 . 6 3 0 . 0 8 - 7 . . 8 3 2 . 6 1 0 . . 10 - 7 , . 79 2 . 9 3 - 0 . . 22 - 1 3 . . 94 3 . 29 - 0 . . 58 - 14 . 23 148 10 . 8 1 MISSING SOLAR F S J . 149 6 . 34 8 . . 7 1 - 2 . 3 7 - 10 . . 19 8 . . 73 - 2 . . 39 - 1 0 , . 18 9 . 32 - 2 . . 98 - 16 . 92 9 . 34 - 3 . . 0 0 - 17 . . 23 150 12 . 9 7 13 . 9 7 - 1 . 0 0 - 1 1 . . 2 0 14 . 0 0 - 1 . .03 - 1 1 , . 2 1 14 . 8 5 - 1 . 88 - 18 . 8 0 14 . 58 - 1 . 61 - 18 . . 84 151 12 . 7 0 13 . 8 0 - 1 . 10 - 12 . . 30 13 . 76 - 1 . 0 6 - 1 2 . , 27 14 . 5 9 - 1 . .89 - 2 0 . . 6 9 14 . 33 - 1 . .63 - 2 0 . . 47 152 10 . 17 10. . 9 0 - 0 . 7 3 - 13 . . 0 3 10. . 93 - 0 . 76 - 13 , . 0 3 1 1 . 6 0 - 1 . .43 - 2 2 . . 12 1 1 . 5 0 - 1 . . 33 - 2 1 . 8 1 153 10 . 0 6 12. , 57 - 2 . 5 1 ' - 15 . 54 12 . 62 - 2 . 56 - 1 5 . , 6 0 13 . 34 - 3 . 28 - 2 5 . . 39 13. . 15 - 3 . . 09 - 2 4 . . 9 0 154 13 . 6 8 13 . 34 0 . 3 4 - 15 . 2 0 13 . 39 0 . . 29 - 15 , . 3 0 14 . 1 1 - 0 . . 43 - 2 5 . . 8 2 13 . 8 8 - 0 . 20 - 2 5 . . 10 155 10 . 0 9 9 . , 26 0 . 8 3 - 14 . 36 9 . .27 0 . 82 - 1 4 . . 48 9 . 8 7 0 . 22 - 2 5 . . 6 1 9 . 87 0 . 22 - 2 4 . . 87 156 6 . 8 1 6 . . 67 0 . 14 - 14 . 22 6 . 66 0 . 15 - 1 4 . 33 7 . 17 - 0 . 36 - 2 5 . .97 7 . . 3 1 - 0 . 5 0 - 2 5 . . 37 157 10 . . 25 9 . . 5 1 0 . 74 - 13 . 48 9 . . 5 0 0 . 75 - 1 3 . 58 10 . 0 9 0 . 16 - 2 5 . . 8 1 10 . 0 7 0 . 18 - 2 5 . 20 158 9 . 83 1 1 . 0 0 - 1 . 17 - 14 . 65 1 1 . 0 0 - 1 . 17 - 14 . 75 1 1 . . 6 4 - 1 . 81 - 2 7 . . 62 1 1 . 54 - 1 . 71 - 2 6 . . 91 159 14 . 77 14 . 53 0 . 2 4 - 14 . 41 14 . 51 0 . 26 - 1 4 . 49 15 . 2 3 - o . 46 - 2 8 . . 0 9 14 . 94 - 0 . 17 - 2 7 . . 08 160 7 , , 73 7 . 34 0 . 3 9 - 14 . 0 2 7 . 33 0 . 4 0 - 14 . 10 7 . 8 3 - 0 . 10 - 2 8 . 19 7 . . 93 - 0 . 2 0 - 2 7 , . 28 16 1 9 . . 9 0 8 . 52 1 . 3 8 - 12 . 64 8 . 5 0 1 . 4 0 - 12 . 69 9 . . 0 1 0 . 89 - 2 7 . 3 0 9 . . 0 5 0 . 85 - 2 6 . . 43 162 14 . 35 MISSING SOLAR F S J . 163 14 . 7 0 MISSING SOLAR F S J . 164 5 . . 8 2 MISSING SOLAR FSJ . 165 6 , . 0 0 MISSING SOLAR F S J . 166 10 . . 9 2 MISSING SOLAR FSJ . 167 7 . . 34 MISSING SOLAR FSJ . 168 13 . 0 4 MISSING SOLAR F S J . o 00 DAY OSTAR EST 1 ERR 1 ERSUM EST2 ERR2 ERSUM EST3 ERR3 ERSUM EST4 ERR4 ERSUM 169 10 .00 MISSING SOLAR F S J . 170 1 1 . 18 MISSING SOLAR F S J . 171 9 . 46 MISSING SOLAR F S J . 172 14 .08 MISSING SOLAR F S J . 173 14 . 36 MISSING SOLAR F S J . 174 16 . 16 MISSING SOLAR FSJ . 175 9 .41 MISSING SOLAR F S J . 176 13 .21 MISSING SOLAR F S J . 177 16 . 32 MISSING SOLAR F S J . 178 12 .94 MISSING SOLAR F S J . 179 14 . 34 MISSING SOLAR F S J . 180 14 .83 MISSING SOLAR F S J . 181 14 . 77 MISSING SOLAR F S J . 182 2 . 10 MISSING SOLAR F S J . 183 3 .88 MISSING SOLAR F S J . 184 15 .21 MISSING SOLAR F S J . 185 13 . 56 MISSING SOLAR FSJ . 186 15 .82 MISSING SOLAR F S J . 187 16 . 47 15 .46 1 .01 - 1 1 .63 15 .62 0 .85 -11 .84 15 .54 0 .93 -26 .37 15 . 23 1 .24 -25 . 20 188 5 . 72 9 .61 -3 .89 - 15 .51 9 .63 -3 .91 -15 . 75 9 .82 -4 . 10 -30 . 47 9 . 82 -4 . 10 -29 . 29 189 15 .07 12 . 27 2 .80 - 12 .71 12 . 33 2 .74 -13 .01 12 .41 2 . 66 -27 .81 12 . 27 2 .80 -26 .49 190 16 . 44 15 . 30 1 . 14 - 1 1 . 57 15 . 37 1 , .07 -11 ,94 15 .43 1 . .01 -26 . 80 15 . 13 1 . .31 -25 . 19 191 5 .51 MISSING SOLAR F S J . 192 6 . 16 MISSING SOLAR F S J . 193 8 . 36 9 .35 - 0 .99 - 12 .56 9 . 37 -1 , .01 -12 .94 9 .51 -1 , . 15 -27 .95 9 .52 -1 . 16 -26. . 35 194 2 . 58 2 .69 - 0 . 1 1 - 12 .68 2 .70 - 0 , . 12 -13. .06 2. .93 - 0 , . 35 -28 .30 3 . 29 - 0 . .71 -27 . .05 195 7 , . 44 8 .07 - 0 .63 - 13 .31 8 . 17 -0 . . 73 -13, . 78 8 . 20 - 0 , .76 -29 .06 8 . 28 - 0 . .84 -27 , .89 196 14 . 10 14 .21 - 0 . 1 1 - 13, .43 14 .41 -0 , .31 -14 .09 14 . , 10 0, .00 -29 .06 13 .87 0. . 23 -27 , .66 197 15 . 58 1 1 .94 3 .64 - 9 , .79 12 .08 3 , .50 -10 . 59 1 1 . .87 3 , .71 -25 . 34 1 1 . 76 3 . 82 -23 , .84 198 13 . 42 13 .01 0 .41 - 9 . . 37 13 .21 0. .21 -10, . 38 12 . , 78 0, 64 -24 .70 12 .62 0. 80 -23 , .04 199 14 . 85 14 . 83 0 .02 - 9 , . 35 14 . 97 -0 . . 12 - 10 . 50 14 . 33 0, . 52 -24 . 18 14 .09 0. 76 -22 , . 27 200 13 . 95 14 . 87 -0 .92 - 10 . 27 15 . 05 - 1 . 10 -11 .60 14 . 56 - 0 . .61 -24 . 79 14 .31 - 0 . 36 -22 . 63 201 15 . 23 14 . 15 1 .08 - 9 , . 19 14 , . 24 0. 99 -10, .61 13 , .91 1. . 32 -23 .47 13 .69 1 . .54 -21 . .09 202 15 . 51 13. .11 2 .40 -6 , . 78 13. . 22 2 . 29 -8 , . 32 13 . 08 2. .43 -21 .03 12 .90 2 . 61 -18 . 48 203 10. . 80 1 1 . .57 -0 .77 -7 , . 55 1 1 . . 58 - 0 . 78 - 9 , . 10 1 1 . .56 - 0 . .76 -2 1 . . 79 1 1 .46 - 0 . 66 -19 . 14 204 1 1 . .98 7. .32 4 .66 -2 , .89 7 . 33 4 . 65 -4 , .45 7 . ,41 4 . 57 -17 . . 22 7 .53 4. .45 - 14 . 70 205 10. .31 12. .81 -2 .50 - 5 , .39 12 . 81 -2 . 50 -6 , .95 12 . 73 -2 . 42 -19 . .64 12 . 57 -2 . , 26 -16 . .96 206 15 , .02 14 . , 54 0 .48 -4 , 91 14 . 42 0. 60 -6 , . 35 14 . 22 0. .80 -18. .84 13 .99 1 . .03 -15 . 92 207 14. .04 13. . 72 0 .32 -4 , , 59 13 , 86 0. 18 -6 , . 17 13 . 56 0. .48 -18. . 36 13 . 36 0. 68 - 15 . , 24 208 13 . 05 13, ,36 - 0 .31 -4 , .90 13 . 49 - 0 . .44 -6 , .61 13. . 10 - 0 . 05 -18. .41 12 .92 0. , 13 -15 . . 12 209 6 . 00 MISSING SOLAR F S J . 210 1 1 . . 24 MISSING SOLAR F S J . 211 13 , 20 MISSING SOLAR F S J . 212 12 . 83 13. .01 - o . 18 -5 , .07 13 , 07 - 0 . 24 -6 , .85 12 . 75 0. 08 - 18 . 33 12 . 59 0. 24 - 14 . 88 213 10. 97 9. , 75 1 .22 -3 , .85 9 , 79 1 . 18 -5 . 67 9 . 66 1 . 31 -17 .03 9 .67 1 . 30 -13 . 58 214 9 . 00 9 . 47 -0 .47 -4 , . 32 9 . 49 - 0 . 49 -6 . . 16 9. 4 1 - 0 . 4 1 -17, . 44 9 .42 - 0 . ,42 - 14 . ,00 215 5 . 67 6 . ,08 - 0 .41 -4 , . 73 6 . ,08 - 0 . 41 -6 , .57 6 . 10 - 0 . 43 - 17 .87 6 . 29 - 0 . 62 - 14 . ,63 DAY OSTAR EST 1 ERR 1 ERSUM EST2 ERR2 ERSUM EST3 ERR3 ERSUM EST4 ERR4 ERSUM 216 7 . 74 7 . . 16 0 .58 -4 . 15 7 . 16 0. .58 -5 .98 7 . . 15 0. . 59 - 17 . 27 7 . 29 0. .45 - 14 . 17 217 6 . 32 5. .70 0 .62 -3. . 53 5 .70 0. .62 -5 .37 5. . 74 0. . 58 -16 .69 5 . 95 0. . 37 -13 .80 218 5 .50 5 .27 0 . 23 -3 .31 5 .27 0 . 23 -5 . 14 5. .31 0. . 19 -16. .51 5 . 55 -0. .05 -13 .85 219 8 .01 10. . 58 -2 .57 -5 .88 10 .60 -2 . , 59 -7 . 73 10. .43 -2 . 42 -18 .92 10 . 39 -2 . 38 - 16 . 23 220 13 .21 MISSING SOLAR FSJ. 221 13 . 77 • MISSING SOLAR FSJ. 222 1 1 .80 10. ,62 1 . 18 -4 .70 10. . 75 1 . .05 -6 .68 10. .41 1 . . 39 -17. . 53 10, . 37 1 , 43 -14 .80 223 13 . 10 1 1 . . 77 1 . 33 -3. .37 1 1 . .85 1 . , 25 -5 .43 1 1 . 49 1 . .61 -15 . 92 11. . 40 1 . 70 - 13 . 10 224 12 . 41 1 1 . .97 0 . 44 -2 .94 12 . 10 0, 31 -5 . 12 1 1 . . 72 0. .69 -15 . , 23 11. 61 0. 80 - 12 . 30 225 12 .97 1 1 . .93 1 .04 -1 .89 12 .00 0. ,97 -4 . 14 1 1 . 68 1 . . 29 - 13 .93 11. . 58 1 . 39 -10 .91 226 12 , . 16 1 1 . . 93 0 . 23 - 1 .66 1 1 . .97 0. . 19 -3 . 96 1 1 . 63 0. 53 - 13 . ,40 11. . 53 0. 63 - 10. 28 227 1 1 . . 79 1 1 . 25 0 .54 -1 . 12 1 1 . . 38 0. .41 -3. . 55 10. 92 0. 87 -12. . 53 10. .86 0. 93 -9 . 34 228 1 1 . . 70 1 1 . .25 0 .45 -0. .67 1 1 , . 35 0. 35 -3. .21 10. 87 0. 83 -11. . 70 10. 81 0. 89 -8 .46 229 12 . 08 10. 97 1 . 1 1 0 .44 1 1 , . 13 0. 95 -2 . 25 10. 62 1 . 46 -10. . 24 10. . 57 1. 51 -6 .95 230 1 . . 74 1 . 85 -o . 1 1 0 . 33 . 1 , .85 -0. 1 1 -2 , 36 1 . 96 -o. 22 -10. .47 2 . 37 -0. 63 -7 . 59 231 10. .50 9. 63 0 .87 1 . 20 9 . ,66 0. 84 - 1 , . 53 9. 45 1 . 05 -9 . 41 9. .46 1. 04 -6 .55 232 10. .09 10. 73 -0 .64 0. .56 10. .78 -0. 69 -2 , 22 10. 44 -0. 35 -9. 76 10. 40 -0. 31 -6 . 86 233 12 . 00 1 1 . 28 0 . 72 1. .28 1 1 . 41 0. 59 - 1 , .63 10. 96 1 . 04 -8 . 72 10. 89 1. 1 1 -5 . 76 234 1 1 . 50 9 . 83 1 .67 2 . 95 9 . 90 1. 60 -0, ,04 9. 57 1 . 93 -6. 79 9. 58 1. 92 -3 . 83 235 2 . 75 2 . 17 0 .58 3 . 53 2 . 17 0. 58 0. .54 2 . 26 0. 49 -6 . 30 2 . 66 0. 09 -3 . 74 VARIANCE OF ESTIMATE 1=2.438 VARIANCE OF ESTIMATE2=2.387 VARIANCE OF ESTIMATE3=3.021 VARIANCE OF ESTIMATE4=3.036 - I l l -APPENDIX 5. Forage P r o d u c t i o n a t Sunset P r a i r i e i n 1977, 1978 and 1979. - 112 -Forage p r o d u c t i o n a t Sunset P r a i r i e i n 1977, 1978 and 1979. A. Accumulated Hay Growth a t S i t e 1 ( t o n n e s / h e c t a r e ) 1977 Date Growth 1978 Date Growth 1979 Date Growth May 31 1.32 June 7 2.74 June 7 1.79 14 3.24 June 18 0. 74 21 5.26 23 3. 43 28 5.29 J u l y '5 12 5. 82 J u l y 4 4.18 J u l y 5 1.99 19 7. 62 • 20 4. 69 16 3. 03 26 Aug. 2 7. 52 Aug. 1 5.59 30 4.07 8 8.10 11 16 4. 82 4. 96 Aug. 13 5. 20 B. Cut Growth a t S i t e s 1 t o 7 i n 1979, ( t o n n e s / h e c t a r e ) S i t e 1 F e r t . 4 4 F e r t . 6 F e r t , June 18 0. 74 0. 27 0. 41 0. 84 , 1. 42 0. 58 0. 40 1.02 1.17 J u l y 16 0. 84 0. 47 0. 50 0. 49 , 1. 37 0. 71 0. 87 1.63 1.31 T o t a l : .1. 58 0. 74 0. 91 1. 33 2. 79 1. 2 9 1.27 2.65 2.48 Aug. 13 1. 11 0. 68 0. 68 0. 47 0. 82 0. 75 1.69 T o t a l : 2. 69 1. 42 1. 59 1. 80 3. 61 2. 04 3. 17 Aug. 2 4 0. 65 0. 45 0. 28 0. 40 0. 84 0. 81 T o t a l : 3. 34 1. 87 1. 87 2. 20 4. 45 2. 85 — — — — 

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