氮肥运筹和少免耕对麦田氮素径流流失的影响

Effects of nitrogen fertilizer application and no tillage on nitrogen loss by surface runoff during the wheat growing season in Intensive Rice-Wheat Rotation Field

采用田间小区定位试验研究了自然降雨条件下氮肥运筹和少免耕措施对稻麦两熟农田麦季氮素径流流失特征的影响。结果表明:自然降雨后麦田耕层土壤平均水分质量分数26.34%为径流事件发生的临界土壤水分质量分数。常规施肥(T0)条件下,麦季径流水量达2185.05 m3·hm-2,径流侵蚀泥沙量达716.08 kg.hm-2,少免耕(T2)处理增加麦田径流水量达29.67%,减少径流侵蚀泥沙量达13.96%,而肥料运筹(T1)与T0处理差异不显著;就整个麦季而言,T0处理条件下,径流水全氮(TN)平均质量浓度和径流侵蚀泥沙TN平均质量分数分别为10.51 mg·L-1和1.19 g·kg-1,T1处理显著降低径流水TN质量浓度和侵蚀泥沙TN质量分数分别达11.63%和5.93%,T2处理显著降低径流侵蚀泥沙TN质量分数达7.95%;麦季氮素径流流失主要集中在小麦生育前期,包括径流水氮素流失量和径流侵蚀过程中由泥沙流失的氮素量。T0处理条件下,氮素流失总量达31.76 kg·hm-2,其中,径流水氮素流失量占麦季氮素总流失量95%以上,T1处理减少麦季氮素总流失量达9.25%,而T2处理则增加麦季氮素总流失量达16.75%。

Field plot experiment was carried out to study the effects of nitrogen fertilizer application and no tillage treatments on nitrogen loss by surface runoff during the wheat growing season of intensive rice-wheat double-cropping system under natural rainfall conditions.The results showed that 26.34% of average water content in the plough layer soils of wheat field was the threshold of surface runoff events.The total volume of surface runoff water and the total quantity of erosive soils by surface runoff reached 2185.05 m3.hm-2 and 716.08 kg.hm-2 during the whole wheat growing season,no significant differences were found between the conventional fertilization（T0） and nitrogen fertilizer application（T1） treatments.However,no tillage（T2） treatment significantly increased the total volume of surface runoff water by 29.67%,and it significantly reduced the total quantity of erosive soils by surface runoff,decreased by 13.96%.Under T0 condition,average TN concentrations of runoff water and erosive soils by surface runoff reached 10.51 mg.L-1 and 1.19 g.kg-1 during the whole wheat growing season,T1 treatment significantly reduced them by 11.63% and 5.93%,respectively.Furthermore,T2 treatment significantly reduced the TN concentration of erosive soils by surface runoff by 7.95%;Nitrogen losses by surface runoff（runoff water and erosive soils by surface runoff） were mainly distributed in the earlier wheat growing stage,including overwintering period and regeneration period.Under T0 condition,the total quantity of TN loss by surface runoff reached 31.76 kg.hm-2,in which the percentage of TN loss by surface runoff water reached 95%,T1 treatment significantly reduced the quantity of nitrogen loss by 9.25%,T2 treatment increased it by 16.75% during the whole wheat growing season.