不同施肥水平下菜地径流氮磷流失特征

研究施肥对菜地径流氮、磷流失的影响,对控制水体富营养化有重要意义。采用田间小区监测的方法,研究常规施肥、减量施肥1和减量施肥2等三种施肥水平对菜地径流氮磷流失的影响。结果表明,（1）不同施肥水平的径流氮、磷流失浓度均较高,径流TN、NH4＋-N、NO3--N的平均流失质量浓度分别在20.5~34、2.2~2.4、6.3~9.5 mg L-1之间,径流TP、DP的平均流失质量浓度分别在7.7~11.1、2.1~2.4 mg L-1之间,菜地土壤径流氮、磷流失风险较大。（2）减量施肥可明显降低径流TN和NO3--N的流失浓度,与当地常规施肥相比,减施肥料20%和30%可分别降低径流TN流失浓度的40%、32%和NO3--N流失浓度的23%、35%,而减量施肥对径流TP、DP的流失浓度影响不大。（3）不同施肥水平的径流TN、NO3--N流失负荷分别在5.8~7.6、1.6~2.3 kg hm-2之间,与常规施肥相比,减施肥料20%和30%可分别减少TN、NO3--N流失负荷的24%、19%和11%、29%。不同施肥水平的径流TP、DP流失负荷分别在1.7~2.9、2.5~2.7 kg hm-2之间,减量施肥并不能减少径流TP、DP的流失负荷。

Characteristics of nitrogen and phosphorus loss by runoff from vegetable fields under different fertilization levels

Analysis of nitrogen and phosphorus losses by runoff from vegetable fields under different fertilizer levels has significance for control of eutrophication in surface. Based on a field plot experiment, three fertilizer scenarios were defined as： normal fertilizer level, fertilization decrease 1 and fertilization decrease 2. The results indicated that, （1） the content of nitrogen and phosphorus in runoff water was relatively high corresponding to different fertilization levels in the vegetable field. The contents of TN, NH4-N, NOf-N were 20.5-34 mg.L1, 2.2-2.4 mg.L-1, and 6.3-9.5 mg＇L1 in runoff water respectively; and that of TP and DP were 7.7-11.1 mg.L-1 and 2.1-2.4 mg＇Lk The risk of pollution to water due to nitrogen and phosphorus losses from vegetable fields was high. （2） Decrease of fertilization could significantly decrease the contents of TN and NO3-N in runoff water from vegetable field. In comparison with normal fertilization, decrease of fertilization by 20% and 30% could decrease the contents of TN by 40% and 32% and NOf-N by 23% and 35% respectively. However, decrease of fertilization had no observable influences on the contents of TP and DP in runoff water. （3） The loss loads of TN and NO3--N by runoff under different fertilization conditions were 5.8-7.6 kg＇hm2 and 1.6-2.3 kg＇hm-2 in the vegetable fields, respectively. In comparison with normal fertilization, the decrease of fertilization by 20% and 30% could decrease the loss loads of TN by 24% and 19% and NO3-N by 11% and 29%. With different fertilization levels, the loss loads of TP and DP by runoff were 1.7-2.9 kg-hm-2 and 2.5-2.7 kg-hm1 respectively, and decrease of fertilization could not decrease the loss loads of TP and DP.