I N T R 0 D U C T I O N
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INTRODU CTION
I n d i a has made commendable p ro g ress in enhancing a g r ic u lt u r a l p ro d u c tio n and p r o d u c t iv it y d uring the l a s t few decades by in t r o d u c in g short-duration high y i e l d i n g s t r a in s of c e r e a l s . I t is d e s ir a b l e t h a t p ro du ctio n of o i l and p u ls e crops b e a lso enhanced in order to in c rea se the consumption of energy p r o t e in and f a t in th e cereal- b ased d i e t of the common m asses. U nfo rtu n a tely th e produc
tio n o f o il s e e d s and p u ls e s has in c re a se d by only 15 p e r cent# w hile that of cereals has in c re a se d by 105 p e r cent, d u r in g the l a s t th ree decades (Pushpamma and Chittemma Rao, 1 9 8 1 ) . The consumption of p r o t e i n and f a t i s much below the average requirem ents due to low a v a i l a b i l i t y . I n a d d i t i o n to th e in c re a se d demand, th e In d ia n p o p u la tio n is expected to sw ell to 935 m il l i o n and the t o t a l food grain s requirem ent is a n t ic ip a t e d to b e about 20 5 m i l l i o n tonnes by the turn of t h is cen tu ry ( Swaminathan, 1 9 8 2 ) . These two facto rs c l e a r l y in d ic a t e the urgent need fo r the b a lan c e d in c r e a s e in a g r i c u l t u r a l o u tp u t. The scope for in c r e a s e in the h o r iz o n t a l p ro d u c tio n b e in g l im it e d , the s i t u a t i o n r i g h t l y c a l l s f o r in c r e a s in g the v e r t i c a l p r o d u c tio n by in tro d u c in g advanced, v i a b l e te ch n o lo g y .
T h e e a s t e r n p a r t of I n d i a i s i n the h ot hum id su b tro p ics and receiv e s about 70 p e r cent of the annual r a i n f a l l (1 5 0 0 mm) th ro ugh heavy showers d u r in g J u n e to September# w h ile the w in ter months exp erien ce o c c a s io n a l l i g h t showers fo llo w e d by an abrupt r i s e i n tem perature beyond m id- February. T h is c l i m a t ic c o n d it io n fa v o u rs a
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rice- based crop ro tatio n vfoich is cu rr e n tly in p r a c t i c e . H e nc e, c u lt iv a t io n of r ic e in k h a r if is a s u i t a b l e option
in t h is r e g io n . A t p resen t r ic e i s being c u l t iv a t e d in 8 7 .2 p e r cent of the t o t a l c u l t i v a t e d area under food g ra in s round the year# and out of t h is about 81 p e r c e n t
is grown in kharif# 5 p e r cen t in r a b i and the r e s t i n summer seaso n . C u l t iv a t e d area under wheat# m ustard and chickpea are only 3 .5 8# 2 .7 3 and 1 .0 8 p e r cent# re s p e c ti
vely# of the to ta l c u l t iv a t e d area under food grains#
which in d ic a t e s the low area u nd er these crops (A n o n . 1 9 8 3 ) . T h ere is c o n s id e r a b le scope fo r in c r e a s in g the area under crops h a v in g low water requirem ents by u t i l i z i n g th e
e x i s t i n g a v a ila b le w ater and by d ra w in g upon more a v a i l able ground of- su rface w ater r e s o u r c e s . Also# the s u b s t i t u t io n of th ese crops fo r r ic e i n r a b i season can b rin g more a re a under c u l t i v a t i o n with the same a v a i l a b l e water
resources and# in turn# in c rea se the total p r o d u c t io n .
F o r a fecund crop p l a n n in g i t is im perative to
ev o lve v i a b l e p ac kag e of p ractices# w ith s u it a b le f e r t i l i z e r requirem ent and tim ing of ir r ig a tio n # ta k in g in t o c o n s id e r a t io n the so il# crop# c lim a t ic and socio-economic stru ctu re of a r e g io n . Optimum time o f sowing# one of the most im portant factors# p r im a r ily depends on the r e s id u a l m oisture r e t a in e d a f t e r the h a r v e s t of the p r e c e e d in g k h a r if rice# the tem perature a t the time of sowing and
s u i t a b i l i t y of c l im a t ic c o n d itio n d u r in g the growth c y cle of the subsequent crop# in p u t resources# and need of the
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fa r m e r s . Farmers in e a s t e r n I n d i a in v a r ia b ly grow ea rly , medium and la t e d u ra tio n rice v a r i e t i e s because of adequate
r a i n f a l l # la n d s it u a t io n and con gen ial environment during k h a r if s e a s o n . T h is p r a c t ic e of c u l t i v a t i o n v ac a te s the la n d f o r subsequent r a b i crops at d i f f e r e n t tim es. I n addition# th e water lo g g in g due to la t e rains o r lo w la n d s it u a t io n creates an u n s u ita b le s o i l c o n d itio n f o r la n d p re p a ra tio n b efo r e November# which delays the sowing of the subsequent ra b i c r o p s . I n general# t h e e ffe c t s o f delayed p l a n t i n g o f d i f f e r e n t crops are d i f f e r e n t and depends on
the c lim a t ic co n d itio n s of the r e g io n . The l a t e sown ra b i crops do not perform w e l l , because they experience short duration w in te r fo llo w ed by an abrupt r is e in tem perature beyond mid-February c a u s in g low y i e l d of the c r o p s .
Farmers a r e , th erefo re# re lu c ta n t to grow r a b i crops and g e n e r a lly keep lan d f a l l o w or w herever s u f f i c i e n t w ater is a v a il a b l e they grow winter/sum m er r i c e . Thus# the a d ju s t ment of sow ing time to ach iev e an optimum y i e l d o f a crop becomes a v i t a l c o n s id e r a t io n .
T he u se of commercial f e r t i l i z e r s i s , perhaps# the most important s in g le fa cto r in b r i n g in g about in c r e a s e in p r o d u c t io n . Even the f u l l b e n e f i t s of i r r i g a t i o n and t h e
in t r o d u c tio n o f h ig h y i e l d i n g v a r i e t i e s of crops cannot be r e a l i z e d w ithout the use of f e r t i l i z e r s * With v a r i a t i o n in chem ical com position o f s o i l , crops d i f f e r markedly in t h e i r requirem ents o f d i f f e r e n t n u t r i e n t s . A p a rt from -tine s o il an d type o f the cro p , c e r t a i n fa c to r s# p a r t i c u l a r l y s o i l moisture# have b een fo u n d to h a v e a p r o fo u n d in f l u e n c e on
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the response of a crop to f e r t i l i z e r s .
Wheat responds favourably to heavy n itro g e n a p p lic a t i o n . B ut nitrogen is a c o s tly in p u t and hence assessment of i t s p r o f it a b l e l e v e l with optimum phosphorus an d p o ta ssium is d e s i r a b l e . The e v a lu a tio n o f n itro g e n requirement of mustard# a crop r e q u ir in g low n u tr ie n ts with h ig h p r o f i t is also n e ed e d . The chickpea# a leguminous cro p , fix.es atmospheric nitrogen and reduces th e need f o r nitrogenous f e r t i l i z e r s ; it also improves st ru c tu r e and f e r t i l i t y of the s o i l . However, it requ ires s u f f i c i e n t phosphorus and t h e r e fo r e it s optimum phosphorus requirem ent to a ch ie v e maximum y i e l d is an important c o n s id e r a t io n . F u r th e r / the
e f f e c t s o f th ese n u tr ien ts on th e q u a l it y of the crops needs i n v e s t ig a t i o n under t h is Agro-clim at ic c o n d it io n .
The broad p u rp o se of i r r i g a t i o n i s to m in im ize y i e l d reduction due to w ater d e f i c i t . To e x p l o it the f u l l y ie l d p o t e n t ia l of crops, it is p lan n ed to increase irrigated,-
area by about 2 . 5 - 3 . 0 m illio n h e c ta r e s p e r y e a r with a ta rg e t o f about 105 m il l io n h ecta re s t o t a l i r r i g a t e d area b y the y e a r 2000 A . D . (Gautam, 1982) . The p re v a le n t proce
dure f o r s c h e d u lin g of i r r i g a t i o n in v o l v in g both time and depth can be separated into those u s in g d ir e c t measurement of s o i l m oisture and th o s e em ploying p r e d ic t iv e approach b a se d on estim ated crop w ater u s e . O f th e tw o, th e l a t t e r approach b ased on c lim a t ic data appears to be more sound and f e a s i b l e . S in c e e v a p o ratio n from p l a n t and so il i s th e
r e s u lt a n t of a l l th e clim atic elem ents, th e c lim a t o lo g ic a l
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approach may prove t o be the most simple* p r a c t ic a l and e x t e n s iv e method f o r tim ing of i r r i g a t i o n . F u r th e r, th e acreage under c u l t i v a t i o n i n r a b i season w ith th e same a v a ila b l e water resources can a lso be in c r e a s e d .
The s u it a b le sowing tim e alo n g with ju d ic io u s water and f e r t i l i z e r management can ensure high p ro d u c tio n and p r o f i t o f any crop i f the lim it e d a v a i l a b l e water i s sc h e
duled to crops h av in g high :water use e f f i c i e n c y and econo
mic v a l u e s . Th us, inform ation re g a r d in g the s c h e d u lin g of i r r i g a t i o n fo r wheat, mustard and chickp ea h av in g v a r y in g water requirem ent w ill help the farmers and i r r i g a t i o n en gin eers to use the w ater for the most p ro d u c tiv e cro p s .
Swaminathan (1 9 8 2 ) has in d ic a t e d t h a t th e gap between p o t e n t ia l and cu rren t experim ental y i e l d is c o n s id e r a b le . Hence, the immediate pay-off w il l come from an a ccele ra te d
e f f o r t in technology t r a n s f e r . T h e r e f o r e , dem onstration a t fa r m e r 's f i e l d was re q u ired to ad ju d g e the te c h n ic a l
v i a b i l i t y and economic f e a s i b i l i t y in t r a n s f e r r in g the inno
vate d te c h n o lo g ie s fo r t h e i r wide adoption a f t e r d e f i n i n g the optimum sowing tim e, i r r i g a t i o n tim in g s and n u t r ie n t requirem ents of th e c r o p s .
U n d e r u n lim ite d resources f o r maximum p r o f i t of a farm, the crop which g iv es maximum p r o f i t w i l l b e recommen
ded w ith optimum l e v e l s of f e r t i l i z e r s and i r r i g a t i o n along with the s u i t a b l e tim e of so w in g . However, same may not be true u nder l i m i t e d resource c o n d it io n s and th e l e v e l s of d i f f e r e n t in p u ts a lo n g with the d i s t r i b u t i o n of crop may
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be d i f f e r e n t for o b t a in in g maximum p r o f i t fo r a farm .
In general# the farmers of West Bengal are h av in g lim it e d resources s p e c i a l l y with re sp ect to a v a i l a b i l i t y of land# labour# water, f e r t i l i z e r and c a p i t a l . K eep in g above fa c ts i n v iew , th ere is need to develop the resource optim i
z a t io n model fo r d i f f e r e n t farm u n it s for o p tim iz in g the re so u rc es. The use of l i n e a r programming tech n iq u e by sim plex method is more conmon and u nder the p re sen t study the fa r m e r s 1 resources along with th e resu lts o b ta in e d
under the p resen t in v e s t ig a t io n were u t i l i z e d for developing the o p tim iza t io n models for d i f f e r e n t farm u n its and resour
ces c o n d it io n f o r m axim izing the p r o f i t .
In fo rm a tio n on n itro g en requirem ent fo r wheat and m ustard, and phosphorus requirem ent f o r chickpea i s a v a i l
able i n regions where t h e s e crops a r e commonly c u l t i v a t e d . However, very l i t t l e is known on th e n itro g en and phosphorus
requirem ents f o r t h i s region where th e se crops a r e not common and h a v in g sh o rt w in ter p e r i o d s . The a p p l i c a b i l i t y of IW /C P E r a tio approach in tim ing of i r r i g a t i o n f o r ra b i crops has sp ecia l s i g n i f i c a n c e in humid su b tro p ic a l eastern I n d i a where the w in te r r a i n f a l l is u n c e rta in and inadequate, w ater resources a r e lim i t e d in dry months and the clim ate e;xperiences an abrupt r i s e in ev a p o rativ e demand d u r in g the re p ro d u ctiv e phase of the c r o p s . The p res en t approach has a great promise in o p tim isin g i r r i g a t i o n water and n u tr ie n t requirem ent in th is re g io n where the sowing times o f r a b i crops are not d e f i n a b l e .
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Keeping these aspects in view# the p resen t in v e s t i
g a tio n was c a rr ie d out with the f o l l o w in g o b je c tiv e s :
i) To f i n d out the e f f e c t of sowing tim e, f e r t i l i z e r s and schedu ling of i r r ig a t io n s on growth and y i e l d of wheat, m ustard and ch ic kp ea ,
i i ) to f i n d out the e ffe c t o f sow ing tim e, f e r t i l i z e r and sc h e d u lin g of i r r i g a t i o n on N, P and K concen
t r a t io n of the crops at d i f f e r e n t stages and t h e i r uptake,
i i i ) to study the e f f e c t o f sow ing tim e , ' f e r t i l i z e r and sc h e d u lin g of i r r ig a t i o n on s o i l m oisture e x t r a c t io n p a t t e r n , w ate r requirem ent and water u se - e ffic ie n c y of the d i f f e r e n t cro ps,
iv ) to fi n d out and demonstrate the e f f e c t of sowing tim e, f e r t i l i z e r and sc h e d u lin g of i r r i g a t i o n on perform ance of d i f f e r e n t crops at fa r m e r 's
f i e l d , and
v) to optim ize th e r e so u rc e s , namely, l a n d , la b o u r , w ate r, f e r t i l i z e r and c a p it a l for o b t a in in g maximum p r o f i t for a g iven resource c o n d it io n .
