Production Functions and Their Use in Predicting Chickpea Biomass Yields When Grown under Varying Tillage and Sowing Dates in Naivasha, Kenya
Onyari, Charles N.
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The use of production functions as tools for analyzing agronomic relationships and crop growth is gaining importance the world over. Their predictive value in crop adaptation trials for specific agro-ecological sites particularly in semi arid lands is of special interest, but little, if any work is being done with this regard in Kenya. A chickpea (Cicer arietinum L.) cultivar, ICCV 95423 was therefore planted under four tillage systems namely, Conventional (CT), Double Digging (DD), Furrow (FT) and Strip Tillage (ST) and under three sowing dates (two weeks apart) at Naivasha. The aim was to develop evapotranspiration and biomass yield (ET-yield) relationships and determining their potential use in analyzing growth (LAI and DM production) of chickpea. Estimated yields (computed) were produced using the 1st season`s (Jan-May `05) functions and validated with the 2nd season (Jun-Oct ‘05) actual yield data sets. The relationships exhibited very high regression correlation coefficients (R2>0.93) indicating the potential reliability of the functions in predicting chickpea yields. Rate of increase in biomass production per hectare millimeter increase in water use was 17.5kg ha-mm 1. Biomass yields estimated from season II ET data were validated and had a reliability of 0.859 and 0.952 when linear and curvilinear functions were fitted, respectively. The January to June crop produced DM at a higher rate of 685.2 kg ha 1 per unit LAI as compared to 309 kg ha 1 LAI -1 for season II crop. Quadratic functions proved able to account for more variations in DM production than linear functions. They can therefore, be used reliably in analyzing and predicting DM production of chickpea in Naivasha. Chickpea has great agronomic potential for use as a food and forage crop in the dry highlands of Kenya.