Abstract: 【Objective】The characteristics of soil erosion and nitrogen loss in sloping cropland of purple soil during maize (Zea mays L.) growth stage under the rainstorm were investigated to provide a theoretical basis for the predicting and effective preventing of nitrogen loss.【Method】 Simulated rainfall combined with runoff plot experiments were employed during maize seedling stage (1th May), elongation stage (26th May), tasseling stage (27th June) and maturity stage (4th August). According to the feature of the stormy summer months in the purple soil  region of Sichuan province, the characteristics of nitrogen loss in surface runoff, interflow, and sediment were studied during maize growth stage under rainfall intensity of 1.5 mm·min^-1 and the slope gradient of 15°. 【Result】(1) The rate of surface runoff and sediment yield increased with the increasing rainfall duration during maize growth stage, which were the highest within seedling stage, and the lowest within tasseling stage, but the rate of interflow within tasseling stage and maturity stage were the highest and lowest, respectively. (2) The rate of nitrogen loss in surface runoff increased with the increasing rainfall duration and became stable after the rainfall duration of 36 min. The average total nitrogen and dissolved total nitrogen were up to 5.24 mg·m^-2·min^-1 and 4.74 mg·m^-2·min^-1 in seedling stage, respectively. The rate of nitrate nitrogen reached stable after the rainfall duration of 30 min, and the rate of ammonium nitrogen showed volatility with rainfall duration. The rate of nitrate nitrogen and ammonium nitrogen were up to 3.90 mg·m^-2·min^-1 and 0.14 mg·m^-2·min^-1 in elongation stage, respectively. The regression relationship between total nitrogen, dissolved total nitrogen, nitrate nitrogen and surface runoff during maize growth stage were extremely significant. (3) The rate of nitrogen loss in the interflow increased slowly with increasing the rainfall duration. The rate of dissolved total nitrogen and nitrate nitrogen showed the same trend with nitrogen loss within seedling stage, elongation stage and maturity stage, while the rate of ammonium nitrogen showed volatility with time. The rate of total nitrogen, dissolved total nitrogen, nitrate nitrogen and ammonium nitrogen were up to 25.04, 20.34, 16.20 and 0.22 mg·m^-2·min^-1 within elongation stage, respectively. The regression relationship between total nitrogen, dissolved total nitrogen, nitrate nitrogen and interflow during maize growth stage were significant, and the slope of liner was the biggest within elongation stage. (4) The rate of nitrogen loss in sediment yield increased with the increasing rainfall duration, but the increase was the highest in seedling stage, which was up to 0.92 mg·m^-2·min^-1. The regression relationship between nitrogen loss and sediment yield during maize growth stage were extremely significant. (5) The forms of nitrogen loss in the surface runoff were reached the highest in seedling stage and elongation stage. Nitrogen loss in the interflow reached maximum in elongation stage and tasseling stage. Nitrogen loss in sediment yield reached the highest in seedling stage. Interflow was the main source for nitrogen loss and accounted 64.07%−83.39% of the total nitrogen loss. Dissolved total nitrogen was the main form of nitrogen loss in surface runoff and interflow, and nitrate nitrogen was the main form.【Conclusion】 Under the rainfall intensity of 1.5 mm·min^-1 nitrogen loss in surface runoff and interflow were the highest within seedling stage and elongation stage, respectively. Dissolved total nitrogen and nitrate nitrogen were the highest in elongation stage, which could easily lead to the eutrophication in waters. Thus, it is necessary to control surface runoff in seedling stage and interflow in elongation stage to reduce nitrogen loss in the purple soil region.

Key words: maize, surface runoff, interflow, sediment yield, nitrogen loss, purple soil