耕作及轮作对土壤氮素径流流失的影响

5年轮作和1年水平沟耕作试验表明:在不同的坡度上,与传统耕作法相比,水平沟减少产流7%,径流液铵态氮浓度提高19%,流失量达到13.01kg/(km²·a),比传统耕作多流失1.11kg/(km²·a);径流硝态氮浓度减少27%,比传统耕作减少7.68kg/(km²·a);径流硝态氮流失减少量和铵态氮增加量相差6倍,水平沟可减少6.57kg/(km²·a)矿质氮流失;水平沟拦截泥沙25%左右,泥沙中全氮富集率提高13%,土壤全氮流失457kg/(km²·a),平均减少18%;一季黑豆和一季黄豆及两季黑豆和一季黄豆参与的5年轮作周期,土壤侵蚀量仅为896t/(km²·a)和984t/(km²·a),不及糜子和土豆参与轮作周期的1/2.

Soil Nitrogen Loss in Runoff and Sediment as Affected by Level Trench and Crop Rotation

Compared with conventional tillage, level trench might reduce 7% in average of runoff amount on different slope land, the ammonium concentration in runoff increases 19%, its loss amount reaches 13.01 kg/(km²·a), also increases by 1.11 kg/(km²·a), the nitrate concentration in runoff reduced 27%, its loss amount is 16.18 kg/(km²·a) with reduction of 7.68 kg/(km²·a), in conclusion, the soil available nitrogen loss in level trench might reduce 6.57 kg/(km²·a) than that of conventional tillage. Level trench might retain 25% of soil loss, increase 13% of total nitrogen enrichment in sediment than that of conventional tillage, accordingly, soil nitrogen loss amount reaches 457 kg/(km²·a), it also reduces 13% of nitrogen loss than that of conventional tillage. Five years' rotation experiments show the erosion modules of rotation systems with a season black soybean, a season soybean, and two seasons black soybean, a black soybean, reach 896 and 984 t/(km²·a) respectively, their modules are twice less than that of rotation system with broom millet and potato.