黄绵土坡面土壤矿质氮素径流流失与入渗特征研究

采用人工模拟降雨的研究方法，研究了黄绵土坡面土壤矿质氮素径流损失与人渗规律。结果表明，径流损失是土壤矿质氮素流失的主要形式，土壤硝态氮是氮素径流损失的主要形态；土壤矿质氮素在地表流失过程中，随时间的延长累积流失量均不断增大，可用幂函数和对数函数方程进行模拟；降雨16h后，硝态氮发生深层渗漏现象比较明显；坡中部硝态氮发生向下迁移的现象相对严重，而铵态氮径流或泥沙损失主要集中在坡上和坡中部。

Mineral Nitrogen Loss by Runoff and Infiltration in the Loess Soil Slope

Serious soil erosion on slope land of the Loess Plateau results in a great deal of nitrogen loss and restricts local agriculture greatly. In this study, simulated precipitation experiment was conducted to investigate the relationship between runoff and nitrogen loss on slope land. Runoff and sediment were sampled during rainfall and soil profile samples were collected 16 hours after precipitation. For all the samples, nitrate and ammonium were determined. The results showed that both nitrate and ammonium concentrations in runoff decreased with time until reaching a quasi-steady condition at about 20 min, nitrate and ammonium concentrations in sediment decreased with time for the first 12 rain and then increased steadily. Cumulative nitrate and ammonium loss in runoff increased steadily during rainfall, which fitted well with exponential function, cumulative nitrate loss was 50 times of cumulative ammonium loss in runoff. Cumulative nitrate and ammonium loss in sediment fitted well with logarithmic function, cumulative nitrate loss was 1.36 times of ammonium loss in sediment, and the cumulative nitrate and ammonium loss in runoff were 100 times and 3 times larger than that in sediment, respectively. Compared with other positions on the slope, nitrate leached deepest up to 28 cm at the position 230 cm from the summit of the slope, but the ammonium concentration was comparatively lower at this point. Soil mineral nitrogen was mainly carried off by runoff, and nitrate was the main form of lost nitrogen during rainfall. Nitrate leaching loss was obvious and mainly occurred on the middle position of the slope, while ammonium loss by runoff and sediment occurred mainly at up and middle positions.