紫色土坡耕地不同施肥水平下氮随径流流失特征研究

采用径流小区定点监测，研究了紫色土坡耕地“冬小麦-夏玉米”种植模式下不同施肥水平处理氮随径流流失特征。试验结果表明:产流量与降雨量变化趋势基本一致。在同等施肥水平下（583.20 kg/hm²），常规处理（农家肥+化肥）中，总氮、硝态氮及氨态氮的浓度变化不显著，各处理氮流失系数分别为:常规处理1.82%，优化处理2.66%，横坡垄作0.51%，横坡垄作中总氮、硝态氮及氨态氮流失量较优化处理相应减少了60.4%，73.2%，53.9%，较常规处理总氮、硝态氮相应减少28.8%，10.4%，氨态氮增加2.4%。在同等种植模式下（顺坡），增量处理（施肥量增加50%），氮流失系数为2.46%，总氮、硝态氮及氨态氮流失量较优化处理相应增加23.3%，11.1%，69.1%。在外界因素如“前期降水较少、施肥后短期内出现较大强度降雨等”强力干扰下，各形态氮素流失量显著增加，且有随施肥量增加而增大的趋势。

Effects of Different Fertilization Level on N-losses alone with Surface Runoff on Slope Land of Purple Soil

Through monitoring the runoff in plots, the N-loss was studied under different fertilization levels with winter wheat-summer maize rotation on the slope land of purple soil. The results showed that the amount of runoff was consistent with rainfall. Under the same fertilization level (583.20 kg/hm²), for the conventional treatment, the TN, NO₃-N and NH₄-N did not change significantly; the coefficients of N-loss are as follows: 1.82% with conventional treatment, 2.66% with optimization treatment and 0.51% under cross-ridge. Compared with optimization treatment and conventional treatment, the TN, NO₃-N and NH₄-N reduced 60.4%, 73.2%, 53.9% and 28.8%,10.4%,-12.4%, separately under cross ridge treatment. Under the same plantation mode, incremental treatment (fertilizer increase 50%), the N-loss coefficient is 2.46% and the TN, NO₃-N and NH₄-N increased 23.3%, 11.1%, 69.1% compared with optimization treatment. The results also showed that the disturbance under external factors such as little precipitation and a heavy rainfall shortly after fertilization, will increase the N-loss significantly, and the loss increased with increasing fertilization.