摘要：Soil water and nitrogen are two important factors in the agro-ecosystem of the Loess Plateau, China. The ridge-furrow maize system with plastic mulch (RFPM) is a widely used measure to increase crop yield in the Loess Plateau area. The purpose of this study was to investigate the effect of the RFPM on soil water and inorganic nitrogen (N) distribution, especially with regard to the risk and dynamic of nitrogen losses, by using Hydrus-2D. The study was conducted over two consecutive years and consisted of two treatments: (i) the RFPM with the split application of nitrogen in 2013 (160 + 60 kg N ha−1, sowing and jointing stage) and (ii) the RFPM with a one-time fertilizer in 2014 (220 kg N ha−1, sowing stage). The results showed that the dynamic of soil water and nitrogen was clearly illustrated by Hydrus-2D, especially with regard to the nitrogen losses and utilization. The RFPM improved soil water consumption in both the ridge and the furrow; the soil water content was obviously fluctuating during the maize growing season, and the degree of fluctuation decreased as the depth increased. The soil NH4+-N concentration was mainly accumulated in the surface soil layer +15–10 cm; the highest NH4+-N concentrations were 69.12 and 104.62 mg·kg−1 in 2013 and 2014, respectively. The highest NO3−-N concentrations were 130.86 and 198.20 mg·kg−1 in 2013 and 2014, respectively. There was an exchange of NO3−-N between the ridge and the furrow when urea was applied in the furrow. The one-time fertilizer caused a high risk of NH3 volatilization; they were 20.40 and 27.41 kg N ha−1 in 2013 and 2014, respectively, which accounted for 9.27% and 12.46% of the N fertilizer inputs in 2013 and 2014, respectively. The rate of nitrite leaching was higher in the furrow than the ridge. However, a proper ratio of the split application of nitrogen would contribute to the NO3−-N leaching reduction; the NO3−-N leaching amounts were 18.13 and 31.26 kg N ha−1, which accounted for 8.24% and 14.21% of the N fertilizer inputs in 2013 and 2014, respectively. Our study indicates, therefore, that the RFPM with a split application of nitrogen would be more effective for the nitrogen losses; the RFPM is a suitable system for agriculture in the rain-fed area of the Loess Plateau, with the benefits of water-use efficiency and non-point source pollution reduction.
