坡度对坡面土壤矿质氮素水蚀流失负荷的影响

坡度是影响坡面水土流失和土壤养分流失过程的重要因素。室内模拟降雨试验表明,当坡长一定时,不仅土壤侵蚀量存在一个“侵蚀临界坡度”,土壤矿质氮流失量随坡度变化也存在一个“养分流失临界坡度”。试验测定这2个临界坡度均在15°～20°之间。土壤矿质氮地表流失以随地表径流流失为主,约占总流失量的99%。坡面矿质氮总流失量的96%为硝态氮,硝态氮对径流中矿质氮总量的贡献率明显高于在侵蚀泥沙中的贡献率。采取一定的截流措施是控制坡面矿质氮流失的关键。

Soil Mineral Nitrogen Loss in Surface Runoff and Sediment as Affected by Slope Gradient on Loess Slope

Slope gradient has many impacts on soil erosion by water and mineral nitrogen loss in an erosion process.The results from artificial rainfall experiments are as follows.Only in a certain range of slope gradient,the amounts of soil erosion and mineral nitrogen loss aggrandized with the increase in slope gradient.Exceeding the range,how ever,the amounts of the losses decreased.With the same slope length,the crit ical slope gradients for soil erosion and mineral nitrogen loss were validated between 15 and 20.Soil mineral nitrogen loss showed two trends.First,soil mineral nitrogen loss by runoff was much more than that by sediment,being about 99% of the total loss amount.Second,soil nitrate loss in erosion process was the maint rend, being about 96% of the total amount of mineral nitrogen loss.The percent of nitrate lost in surface runoff was much more than that in sediment.Further measures to reduce runoff flow are suggested to control soil mineral nitrogen loss by surface runoff.