Effects of Deficit Irrigation Simultaneously with Reduced Usage of Fertilizer and Chemical Pesticides on Changing Cropping Pattern in Qazvin Irrigation Network

The aim of this study was to determine the optimal cropping pattern in irrigation network of Qazvin plain with emphasis on deficit irrigation policy and reduction of fertilizers and chemical pesticides. For this purpose, the Positive Mathematical Programming approach (PMP) and Maximum Entropy Technique (ME) were used. The results of the first option (5% deficit irrigation in wheat, barley, grain corn, fodder maize and Sugar beet at the ripening stage, and 5% deficit irrigation in the vegetative growth stage for alfalfa simultaneously with5% reduction in fertilizers and chemical pesticides) showed that sugar beet, alfalfa, grain corn and fodder maize were be desirable for cropping pattern due to their high economical profit in compared to wheat and barley. Also, applying this policy leads to an increase in gross margin (4.5%) and a reduction in water consumption (5.1%) in the agricultural lands of the region.As a result of the implementation of the second scenario, the cropping pattern goes towards products that have a higher economic margin due to their lower irrigation water consumption. This scenario leads to 3.6% increase in gross margin and 17.2% reduction in water consumption. Other results of the research showed that due to the application of these policies in PMP, the sustainability indicators of water resources, fertilizers and chemical pesticides are less than the current values for the region's present cropping pattern. The calculated environmental index revealed that high consumption of water, fertilizer, and other chemical inputs are a barrier to achieve sustainable agriculture.