Integrated non-linear model for optimal cropping pattern and irrigation scheduling under deficit irrigation

A non-linear optimization model for deficit irrigation is proposed in the present study to maximize the net financial return within the available resource constraints. The deficit levels of irrigation are kept as variables in the model with a flexibility to keep the crops either at full irrigation or deficit irrigation in order to maximize the net financial return. The model optimizes the deficit levels, cropping pattern and decade (10 days) optimal water withdrawals for the existing land and water resources. The proposed model is applied to Khairpur East canal command of the Lower Indus Basin. The overall optimal net financial return was increased by 92.5% and the total optimal cropped area was enhanced by 109.7% under deficit irrigation as compared to the existing cropping pattern although the net financial return per hectare of land was reduced under deficit irrigation. The optimal net financial return can further be increased by 17.5% if the existing tube well capacity is augmented by 75% in the command area. The surface water availability was also reduced to work out its impact on the optimal cropped area. Although the net financial returns reduced with a reduction in the surface water availability but the optimal irrigated cropped area remained almost the same under deficit irrigation. However the cropping pattern and optimal deficit levels of different crops changed as the surface water availability is reduced. Further, a balanced optimal production of crops would require imposing upper and lower constraints on the quantity of the production of crops in place of crop areas under deficit irrigation.