Assessment of Agricultural Water Productivity for Maize in Evan Plain (Case Study in Sought Karkheh River Basin)

This study was conducted to assess yield، water consumption، and water productivity of maize and the factors affecting it under farmers’ management conditions at the Karkheh River Basin، Iran، during 2006 and 2007 growing seasons. The studied farms were in Evan Plain that is located in the northern part of the lands downstream of the Karkheh River Dam، where summer maize is planted in 75 cm spaced rows and irrigated by furrows. During the two years of the research and considering the prevailing diversity of the sources of irrigation water (Based on the ratio)، seven irrigated field units were selected as follows: two units using groundwater (wells)، three units receiving surface water from irrigation network، one unit taking water directly from the river، and one unit using network and well water. In each irrigation unit، three farms were chosen with regard to irrigation and farming management. In the field trials، some physical and chemical properties of the soil، soil test for nutrition (NPK) availability، the volume of inflow applied to the field by the farmer and runoff water in each irrigation، and total crop yield was measured and maize evapotranspiration was calculated. Then، the irrigation and rain water productivity (WPI+R)، water application efficiency (WAE)، and maize crop water productivity (CWP) was determined for each field. Based on the two years results، the average yield of maize kernel، WPI+R، WAE، and CWP values were، 4844 kg/ha، 0. 38 kg/m3، 38. 6،%، and 1. 01 kg/m3، respectively. The results and observations made during this study indicated that the most important reasons for low water productivity were inadequate knowledge of farmers in irrigation، plant nutrient deficiencies، and improper crop management practices.