Investigation of Soybean Irrigation Water Productivity in Farms of Golestan Province

The current study aimed to measure the water use and water productivity in 44 soybean farms (37 irrigated and 7 rainfed farms) under the management of farmeres in 3 regions including Gorgan, Aliabad, and Kordkuy-Bandar Gaz in Golestan province in 2020. Required information including physicochemical properties of soil and water, irrigation method, volume of irrigation water and cultivation properties were measured. Results showed that in the mentioned regions only 13, 7 and 28 percent of farms were irrigated by sprinkler irrigation and others were irrigated by surface irrigation, respectively. The volume of water use was measured by flume in the surface irrigation and was determined by measuring water flow in the sprinkler irrigation and were compared with the soybean water requirement. Results showed that the net water requirement of soybean in 2020 for Gorgan, Aliabad and Kordkuy-Bandar Gaz regions was 593, 435 and 516 mm for planted in spring, and was 525, 398 and 486 mm for planted summer, respectively which compared to when long term meteorological values are used is increased by about 25 and 22 percent and 45 and 64 percent to National Water Document values for planted in spring and summer. The mean irrigation water use in 2020 in Gorgan, Aliabad and Kordkuy-Bandar Gaz was 4460, 4620 and 1500 cubic meters per hectare, respectively and in these regions, 80%, 45% and 100% of farmers applied deficit irrigation, respectively. The rainfall provided 20, 21 and 33 percent of irrigated soybean water requirement in Gorgan, Aliabad and Kordkuy-Bandar Gaz, respectively. The average applied water productivity in Gorgan and Aliabad was 0.46 and 0.51 kg/m3 and in Kordkoy-Bandar Gaz was 1.6 kg/m3 for irrigated farms and 2.9 kg/m3 for rainfed farms.