紫色土壤氮素不同流失形式的比较研究

土壤氮素流失形式及其量化研究是农业小流域氮素管理及流失过程模拟的核心内容之一，以紫色土区3个具有不同地形和土地利用方式的典型农业小流域为研究对象，比较研究了区域土壤氮素在降雨侵蚀过程中流失的主要形式。结果表明，紫色土区土壤氮素以硝态氮为主要流失形式，其流失浓度一般占硝态氮和铵态氮总浓度的80%以上，农田利用为主流域的则高达90%以上。氮素流失的平均浓度因流域土地利用类型的差异而显著不同，农田的一般为(5.36±2.13) mg/l，而非农田利用的变化在1.70~3.15 mg/l之间。农田硝态氮的精确管理应作为减控流域土壤氮素非点源流失的关键措施。

Comparative Study of N loss form by Runoff in Purple Soil Agro-watersheds

The objective of this paper was to investigate and quantify the main form of N loss by runoff, and finally to serve for the N management and loss simulation. Three agro-watersheds with different land use type and terrain were taken examples to investigate the main form of N loss by runoff under erosion of natural rainfalls in purple soil region. Results showed that nitrate nitrogen was the main form of N loss by runoff. Generally, nitrate nitrogen concentration in runoff accounted for 80 percent of N loss, even above 90 percent in farmland-dominated watersheds. In addition, the average concentration of N loss was (5.36±2.13) mg/l in farmland-dominated watersheds, while behaving from 1.70 to 3.15 mg/l in woodland-dominated watersheds and watersheds with various landscape structures. This showed that precise management of nitrate nitrogen in farmland-dominated watersheds was a key practice for control and reduction of agricultural non-point source N loss.