Yield and water-saving effects of winter wheat based on variable rate irrigation dynamic zoning management

Infrared thermometers (IRTs) is one of the most important tools that mounted on the moving sprinkler irrigation. The water stress of crop can be dynamically monitored to construct the decision-making on the variable rate irrigation (VRI) of center pivot irrigation. This study aims to evaluate the application performance of IRTs in dynamic zoning management. The prescription maps were also constructed using IRTs. A systematic investigation was implemented to explore the influences of VRI decision with meteorological parameters, soil moisture sensor network and canopy temperature on irrigation scheduling, soil water content distribution, water saving and wheat yield. A comparison was then made with the uniform rate irrigation (URI) decision with the meteorological parameters and soil moisture sensor network. The experiment was carried out at the intelligent irrigation and equipment innovation demonstration and promotion base of China Institute of Water Resources and Hydropower Research, Dacaozhuang, Xingtai, Hebei Province of the North China Plain in 2021 and 2022. The two years were both dry years. The experimental area was 7.07 hm² that controlled by a three-span center pivot VRI system with an overhang. Variable-rate water was applied along the lateral and travel direction. The control was realized via the duty cycle of a solenoid valve ahead of each sprinkler and the travel speed of the center pivot. In 2021, the experimental site was divided into two subzones for the URI and VRI treatments. In 2022, the management zones were defined in the treatments of URI, and VRI (T1) with the equal interval , VRI(T2) with the “Jenks” natural break classification, and VRI (T3) with the geometric interval breakpoint, respectively. As such, four subzones were allocated with the equal area. The results indicated that the irrigation times were 7 to 10 in both URI and VRI treatments during the winter wheat growing season in a dry year. Specifically, the average application amount was 201 and 173 mm, respectively, which was greater than the traditional management with 3 to 5 irrigation events of 232 mm application amount. After the dynamic VRI management, the spatial distribution was uniform in the soil water content in the majority of the root zone, leading to the high yield of winter wheat. The wheat yields were 9 470 and 9 574 kg/hm² in URI and VRI treatments in 2021, respectively. The yield and water use efficiency of winter wheat were not significantly decreased (P>0.05). However, the irrigation amount was decreased by 13% and 25% in 2021 and 2022, respectively. The findings can provide the guidance to establish the dynamic zoning management of variable irrigation using IRTs mounted on moving sprinkler irrigation system. A technical support can also be offered to develop and upgrade the decision support system of variable irrigation