Optimization of Applied Water Depth Under Water Limiting Conditions

Water productivity is a major challenge in all agricultural regions and despite water shortages, farmers do not welcome water management strategies due to a lack of knowledge of possible economic consequences. This study aimed to introduce the optimum applied water depths under limiting conditions through mathematical optimization. The effects of optimization were coupled with irrigation scheduling to assess yield, water productivity, and net income. Production and cost functions were created based on two scenarios for the applied water. According to the results, the best applied water depth under water limiting conditions depends on land limiting conditions and how severe water limitation is. In mild to moderate water limiting conditions, by using the optimum applied water depth (W_w), water can be saved by 26% causing a 3 to 4% decrease in the net income per unit of land and a 16% increase in the net income per unit of water. As water supply is severely limited, using the equivalent optimum applied water depth (W_ew) results in the highest productivity. Although using W_ew causes a 14 to 17% decrease in the net income per unit of land, it saves water by 46%. In water limiting conditions, if the land is not limited, using W_ew causes the maximum net income per unit of land. A sensitivity analysis was conducted for the net income and the optimum applied water depths, as well. Furthermore, irrigation scheduling caused a 27% increase in the net income per unit of land. Overall, using optimum applied water depths and irrigation scheduling are highly recommended for addressing water scarcity.