Computer Algorithm for Irrigated Water – Yield Response of Cowpea under Sprinkler Irrigation System

A MATLAB Computer program on cowpea yield was developed to compare the yield obtained from the field under sprinkler irrigation system with the yield predicted by the developed model. Dry season experiment was conducted between January and April of 2014 at Teaching and Research Farm of the Department of Agricultural Engineering, Federal University of Technology, Akure. Soil physical and chemical properties of the experimental site were determined using standard procedures. The cowpea seeds were established on the field and four irrigation water managements were imposed on the crop. An algorithm comprising of existing empirical models from crop production functions were implemented using MATLAB - based computer program. Yield response factor, ky and elasticity of water production (EWP) were also introduced into the algorithm in order to determine the maximum production of cowpea during the growing season of the experiment. The field seasonal yield, crop evapotranpiration and total water applied were input into the model to validate it so as to obtain corresponding model output (predicted yield). The model predicted yield well. The yield results show a good degree of correlation with coefficient of determination r2 equal to 0.96 and 0.98 for linear and quadratic production functions (ETPF) respectively. The optimized water use and yield of cowpea obtained from the developed model during the growing season were 382.34 mm and 0.996 tons/ha. The total amount of water that resulted to the optimum water use and yield was 446.23 mm. This result implies that 92% of total irrigation water applied during the growing season resulted to the optimum production of the crop. The model, therefore, proved to be useful in estimation of possible irrigation water to maximize yield and crop water use of cowpea.