Crop Yield and Water Productivity Responses in Management Zones for Variable-Rate Irrigation Based on Available Soil Water Holding Capacity

Abstract. Effective management of variable-rate irrigation (VRI) is a critical factor for maximizing the benefit of a VRI system. In this study, the influences of soil properties on winter wheat and summer maize were studied to verify whether differences in soil available water holding capacity (AWC) had an influence on crop growth parameters, yield, and water productivity (WP). A center-pivot VRI system was employed to deliver irrigation water across the field in an alluvial flood plain in China, and AWC was used to delineate VRI management zones. Three management zones with substantial differences in AWC were created, with AWC varying from 152 to 161 mm, from 161 to 171 mm, and from 171 to 185 mm for zones 1, 2, and 3, respectively. All zones were managed using the same allowed depletion. In the two-year study, the seasonal irrigation amount was basically equivalent among management zones for both winter wheat and summer maize. Differences in crop growth parameters were detected in plant height and leaf area index for winter wheat. The maximum plant height and leaf area index observed in zone 2 were 5 cm and 2.1 greater, respectively, than in the other zones. For both winter wheat and summer maize, the highest yield and WP were observed in zone 2, except for summer maize WP in the 2014 season. Compared with the average value for this field, the yields in zone 2 were 27% and 23% greater for winter wheat and 4% and 11% greater for summer maize in the 2014 and 2015 seasons, respectively. We demonstrate that AWC is an effective parameter for zone identification in VRI management, and differences in AWC and the layered-textural soils in a field may influence the crop growth parameters, yield, and WP of winter wheat and summer maize. Keywords: Center-pivot irrigation, Critical soil moisture deficit, Management zone, Summer maize, Variable-rate irrigation, Winter wheat.