The Effect of Adoption of Deficit Irrigation Pattern in Farm Level in Ardalan Plain with Emphasis on Water Resources Management

The correct application of deficit irrigation requires thorough understanding of the yield response to water (crop sensitivity to drought stress) and the economic impact of reductions in yield of products. In regions where water resources are restrictive, it can be more profitable for farmers to maximize crop water productivity instead of maximizing the harvest per unit land. Therefore, in the present study the effect of adoption of Clarke's deficit irrigation was evaluated in farms-level in Ardalan plain with emphasis on water resources management. This case were applied using a spatial-aggregation positive mathematical programming (SA-PMP) model and the questionnaire data related to year 2019-2020. After calibration of proposed modeling system in GAMS software, the effects of Clarke deficit irrigation in 5 and 10 percent levels on optimum cropping pattern, consumable water resources and farmers' gross margin were evaluated. The results showed that there is a significant difference between farmers' paid water charges (547 Rials) and economic value of irrigation water (1348 Rials) in Ardalan plain which leads farmers to consider water as a free input and its over-consumption in crop lands. Also, applying the deficit irrigation method leads to a saving of 5.01 to 9.78 percent in irrigation water for only a slight decrease in yield of selected products (from 0.88 to 5.72 percent) and in farmers’ gross margin (from 3.15 to 7.07 percent). More stretchability of water demand in small farm (ewater= 0.573) and increasing the economic value of water from 3.9 to 8.9 percent compared to the base year condition are another consequence of application of deficit irrigation in representative farms pattern. Finally, for a sustainable management of water resources in Ardalan plain it is recommended to use deficit irrigation method at low levels (5 and 10 percent) especially in large farms, to apply the policy program of equality consideration (in order to reduce the gap between the water price and the economic value of water), to modify the pricing system to differentiate the price of water for small, medium and large farms.