丹江口库区坡耕地柑桔园不同覆盖方式下地表径流氮磷流失特征

以坡耕地柑桔园为研究对象，地表覆盖方式采用对照、秸秆覆盖和地膜覆盖3个处理，实验采用完全方案。结果表明，在本实验条件下，坡地地膜覆盖处理一定程度增加了径流量，而秸秆覆盖处理与对照每次降雨径流量基本相当；各处理土壤氮磷养分均有一定程度的流失，以氮素流失量较高，磷素流失量相对较低；在地膜覆盖条件下，柑桔园地表径流中N、P流失量较高，其总氮和总磷流失系数分别达0054%和0064%，而秸秆覆盖总氮和总磷流失系数最低；对不同地表覆盖方式柑桔园地表径流水体氮素形态特征分析表明，可溶性氮素占总氮的比例较高，可溶性氮素中又以NO-3 N为主，而NH+4 N所占的比重较低。以上结果说明，在丹江口库区，氮素污染风险要高于磷，防控的主要矛盾是氮，而秸秆覆盖是减少坡耕地养分流失较好的管理措施

NITROGEN AND PHOSPHORUS LOSS CHARACTERISTICS ON SLOPING LAND RUNOFF IN CITRUS ORCHARD WITH DIFFERENT MULCHING PRACTICES IN THE DANJIANGKOU RESERVOIR AREA

Field in situ investigation was conducted to study the sloping land pathways and processes of water and nutrient movement in the Citrus Orchard in Danjiangkou Reservoir area,China.Three mulching treatments were adopted in the runoff plots,including no mulching (CK,conventional practice) as control,rice straw mulching (SM) and plastic film mulching (FM).Nitrogen (N) and phosphorus (P) losses with surface runoffs were measured during the experimental period.Results indicated that the runoff was increased by the FM treatment,but was not affected much by the SM treatment when compared with the CK treatment after each rainfall.Both N and P losses were presented with runoffs in all of the plots,and the losses were much more in the FM treatment,with the loss ratio of TN and TP being 0054% and 0064% respectively,than that in the SM treatment.Much more nitrogen was lost than phosphorus from the citrus orchard soil with the rainfall runoffs,and the soluble nitrogen occupied much of the total nitrogen loss,primarily in the nitrate form rather than the ammonium form.It was concluded that straw mulching practice was good to keep soil nutrient,specially the nitrogen,in citrus orchard on the sloping land from being lost with rainfall runoffs,and it could reduce the risk of nitrogen pollution to the Danjiangkou Reservoir.