Water use and productivity of maize under different variable rate irrigation managements in sub-humid climates

Abstract. How to make full use of the rainfall and manage the supplement irrigation with variable rate irrigation (VRI) system is critical for the utilization of VRI technology in humid climates. In this research, we evaluated three irrigation management methods for their potential in maximizing the crop yield and water productivity (WP) in managing VRI systems during the growing season of summer maize in the North China Plain. The three irrigation management methods were the soil-water balance modeling (SWB), measured soil water content (SWC), and the combination of soil-water balance method and rain forecast (RF) in the next three days. These irrigation treatments were implemented over four management zones delineated with available soil water holding capacity. The rain-fed treatment was also set in each zone with no additional application except for seedling emergence and aiding fertilization (35 mm). Because of the large spatial variability of soil properties, the water application varied in a larger range among zones in SWC (from 95 mm to 215 mm) than that in SWB (from 155 mm to 175 mm) and RF treatment (from 135 mm to 175 mm). Consequently, the lower yield and WP were obtained in rain-fed treatment, while no obvious differences in yield and WP were obtained among irrigation treatments in each management zone. For a given irrigation management method, the similarly uniform distribution of yield and WP in the field were observed for SWC, SWB, and RF treatments. Our results suggested that both of the SWC, SWB, and RF approaches could be effectively used to manage irrigations under a VRI system in sub-humid climates.