Water Use Characteristics of Increased Plant Density and Reduced Nitrogen Application Maize in Oasis Irrigated Area

In arid irrigation area, the problem of limited water resources, high nitrogen fertilizer input, and low water use efficiency (WUE) in maize production is serious, it’s necessary to investigate the viability of dense planting to compensate for the negative impact of reduced nitrogen application on the water use efficiency of maize, so as to provide academic foundation for the maize production with reduced nitrogen but high water use efficiency.

From 2019 to 2022, a split-plot experiment was carried out in Wuwei, Gansu Province. Two levels of nitrogen application rate, including reduced nitrogen application (N₁, 270 kg·hm^-2) and traditional nitrogen application (N₂, 360 kg·hm^-2) were set in the main plot. Three planting densities, including traditional density (M₁, 78 000 plants/hm²), medium density (M₂, 103 500 plants/hm²), and high density (M₃, 129 000 plants/hm²) were set in the split-plot, N₂M₁ was set as the control. The effects of nitrogen application, plant density and their interaction on water consumption characteristics and water use efficiency of maize were mainly studied.

In the trial year, the water consumption of reduced nitrogen application was 4.7% lower than that of traditional nitrogen application. The water consumption of the combination of reduced nitrogen application and medium density (N₁M₂) was not significantly different from that of the control. The water consumption of high and medium density treatments increased by 8.4% and 4.2% respectively compared with that of traditional density treatment. The grain yield of maize decreased with the reduction of nitrogen application. Medium density could increase grain yield compared with high density and traditional density. The combination of reduced nitrogen application and medium density increased the grain yield compared with the control. In the test year, the grain yield of the reduced nitrogen application treatment was 4.6% lower than that of traditional nitrogen application treatment, the grain yield of the medium density treatment was increased by 5.6% and 8.2% respectively compared with high density treatment and traditional density, and the grain yield of N₁M₂ was 4.3% higher than that of N₂M₁. Reducing nitrogen application reduced IWUE, but maintained the same WUE as traditional nitrogen application; Medium density was beneficial to improve WUE and IWUE, and could compensate for the WUE decrease caused by reduced nitrogen application. In the four study years, the IWUE decreased by 4.5% due to reduced nitrogen application, and there was no significant difference in WUE between the two nitrogen application levels; Compared with the traditional and high density treatments, the IWUE of the medium density treatment increased by 8.6% and 6.4%, respectively, and the WUE increased by 4.5% and 10.1%, respectively; The compensation effects of medium density on the IWUE and WUE were 4.3% and 5.2%, respectively.

In arid irrigation area, applying nitrogen of 270 kg·hm^-2 and density of 103 500 plants/hm² during the whole growth period of maize can increase the yield and water use efficiency compared with the existing water and nitrogen management measures, which is a production technology for nitrogen saving and water efficient utilization of maize in this area.