Water-Use Characteristics of Wheat-Maize Rotation System as Affected by Nitrogen Application Rate in North China Plain

Reducing the nitrogen (N) application rate and improving water-use efficiency (WUE) are extremely important for sustainable agricultural development in wheat-maize rotation systems in the North China Plain (NCP). We conducted a three-year experiment to investigate the effects of the N application rate on the water-use characteristics of wheat-maize rotation systems in the NCP. The experiment consisted of four N application rates: 250, 167, 84, and 0 kg hm-2, denoted by N3, N2, N1, and N0, respectively. The results showed the following: For the 0-60 cm soil layer, N deficiency could lead to reduced soil water use (SWU) in wheat seasons, but in maize seasons, N deficiency showed no significant effects on SWU in the 0-60 cm layer. For the 60-140 cm soil layer, N deficiency could lead to reduced SWU in wheat seasons, but in maize seasons, the effects of N deficiency on SWU in the 60-140 cm layer varied with the SWC in the 0-60 cm layer. Throughout the three-year experiment, the evapotranspiration (ET), leaf area index (LAI), yield, and WUE of plants receiving low N treatments decreased with the growing season due to the negative effects of low N treatment (N1 and N0) on the soil. The LAI, total ET, grain yield, and WUE were all positively correlated with each other for both wheat and maize. Considering grain yield and WUE, a single-season N application rate of 167 kg hm-2 (N2 treatment) in the NCP could meet the growth needs of the wheat-maize rotation system.