Evaluation of Water Application Efficiency and Productivity of Surface Irrigation Systems in Fields of Nazloo-Chay Region, Urmia

Improving water productivity and irrigation efficiency is important in Iran due to limitations in water quality and quantity. This study was conducted to investigate and analyze application efficiency and water productivity at field scale in Nazloo-Chay plain, located in Urmia province, during 2015-2016. For this purpose, five wheat fields, as fall planting, and five fields for spring crops i.e. maize and pumpkin (two fields of each) and sunflower (one farm), were studied. Irrigation system in wheat fields was border, while spring crops were furrow irrigated with closed end condition. To evaluate and measure the water productivity and irrigation efficiency in each irrigation event, some parameters were measured including irrigation depth, system geometry, soil water depletion in the root zone before irrigation (SMD) and the plant parameters. In the five wheat fields, a total of 21 irrigation events were performed and all of which were monitored and evaluated. The average of irrigation efficiency and standard deviation in the 21 irrigation events at these five wheat fields was about 30.9% and 19.5 percent, respectively. For the three spring crops, 27 irrigation events were evaluated and the overall average irrigating efficiencies for sunflower, pumpkin (cucurbita) and maize were about 69.3%, 51.5% and 52.5%, respectively. The average of standard deviation in spring plantings was calculated at about 13.9 percent, which indicates that the scattering of application efficiency was less in spring plantings than fall planting. Based on the results, the average of physical water productivity in wheat fields was 1.1 kg/m3. This index for sunflower, pumpkin (Cucurbita) seed and maize was calculated at about 0.27, 0.17 and 7.02 kg/m3, respectively. Average economic water productivity in wheat was 14512.4 Rial/ m3 and for sunflower, maize and cucurbita seed were 20252.6, 13463.9, and 23305.3 Rial/ m3, respectively, which indicated high economic water productivity for sunflower and Cucurbita seed. Generally, the crop management practices in all fall and spring plantings including fertilizer and pesticides applications were based on scientific recommendations, but irrigation management was poor in all farms. One of the main reasons for low application efficiency in these farms (in particular the fall plantings) was the poor field leveling that required high water depths for irrigation of the fields.