不同管理措施对黄壤坡耕地径流氮输出的控制效果

以黔中黄壤坡耕地氮磷流失长期定位监测基地为平台,于2008—2012年连续5 a进行观测,研究玉米-油菜种植模式下,6种管理措施对黄壤坡耕地地表径流、径流氮输出的控制效果。结果表明:黄壤坡耕地产流系数为15.1%~20.1%,平均18.1%;氮肥流失系数为0.81%~1.34%,平均0.99%;径流氮输出以颗粒态氮所占TN比例46.9%最高,可溶性总氮流失以硝态氮为主,占TN流失的31.1%。优化施肥+横坡垄作+秸秆覆盖+等高植物篱的耕作管理措施截流效果、氮输出控制效果最佳,产流量较CK减少25%;氮肥流失系数最小,为0.81%;TN平均输出总量最小,为4.63kg·hm-2。顺坡常规耕作条件下,优化施肥与常规施肥径流量相当,TN输出量减少23.2%;优化施肥条件下,横坡垄作较顺坡常规耕作径流量减少6.7%,TN输出量减少7.3%;优化施肥+横坡垄作条件下,秸秆覆盖较无秸秆覆盖径流量减少4.8%,TN输出量减少3.4%;秸秆覆盖+等高植物篱较秸秆覆盖径流量减少11.6%,TN输出量减少6.8%。横坡垄作、优化施肥、秸秆覆盖、等高植物篱是控制黄壤坡耕地地表径流、径流中氮输出的有效措施。

Effects of Different Management Practices on Nitrogen Runoff Losses from Sloping Yellow Soil

Runoff losses of nutrients from soils have aggravated water environmental pollution. A long-term experiment with maize-rape rotation was conducted on sloping farming land of yellow soil in Central Guizhou Province from 2008 to 2012. The effects of six management practices on runoff and nitrogen runoff losses were examined. The average runoff coefficient was 18.1% with a range of 15.1%~20.1%. The coefficient of total nitrogen losses ranged from 0.81%~1.34%, with an average of 0.99%. The percentage of particulate N of total nitrogen losses from runoff was the highest(46.9%). Nitrate-N was the dominate form of total dissolved nitrogen with a 31.1% of total nitrogen loss. The best management practice(optimized fertilization+contour cultivation+straw mulch+contour hedgerow) could reduce total nitrogen losses effectively, resulting in 25% less runoff than CK. The total nitrogen runoff losses(4.63 kg·hm^-2) and loss coefficient (0.81%) were both the lowest under this practice. Under conventional down the slope tillage, the runoff from optimized fertilization was almost the same as that from the conventional fertilization, but the former reduced total nitrogen runoff losses by 23.2%. Under optimized fertilization, the runoff and total nitrogen losses decreased by 6.7% and 7.3% respectively in contour cultivation, compared with conventional down the slope tillage. For the practice with optimized fertilization+contour cultivation, the runoff and total nitrogen losses decreased respectively by 4.8% and 3.4% in straw mulch as compared with no straw mulch. Under straw mulch+contour hedgerow, the runoff and total nitrogen losses were respectively 11.6% and 6.7% lower than those under straw mulch alone. Together, the present results suggest that optimized fertilization+contour cultivation+straw mulch+contour hedgerow would be effective management practice for reducing runoff and nitrogen losses in sloping farming land of yellow soil.