紫色土旱坡地油菜/玉米轮作下氮流失的年际变化特征

Interannual Variation Characteristics of Nitrogen Loss Under Rapeseed/Maize Rotation in Purple Soil Sloping Field

明确三峡库区紫色土旱坡地氮流失的年际变化特征,为库区的施肥管理措施和面源污染治理提供参考.依托中国科学院成都山地灾害与环境研究所三峡库区试验站,于2018~2020年连续3 a设置不施肥(CK)、常规施肥(F)、优化施肥(OF)、化肥减量配施生物炭(BF)和化肥减量配施秸秆覆盖(SF)5种处理,研究紫色土旱坡地在油菜-玉米轮作模式下氮流失的年际变化特征.结果表明:1三峡库区紫色土旱坡地地表径流主要发生在5月和8月,壤中流主要发生在6~10月.2018~2020年降雨量逐年增加,各处理地表径流产流量逐年减少,壤中流产流量大致呈逐年增加的趋势,年尺度下,壤中流产流量和产流次数均高于地表径流.22018~2020年每年各形态氮的最高流失浓度出现时间大概一致,地表径流全氮、铵态氮和硝态氮最高流失浓度分别出现在5、8~10和7月,壤中流各形态氮最高流失浓度分别出现在10、10和5~7月.3地表径流各形态氮流失通量呈逐年降低趋势,壤中流各形态氮流失通量大致逐年增加.4生物炭和秸秆还田第一年降低氮流失通量的效果较好,但后续两年还田反而加剧了氮素流失通量.因此,三峡库区紫色土旱坡地施肥时应考虑该区域具有降雨集中性的特点,在氮素流失风险期(5~10月)加强肥料管理,分时期有针对性地施肥,生物炭和秸秆还田的同时采取有效的拦截措施以控制养分流失和农业面源污染.

The aim of this study was to clarify the inter-annual characteristics of nitrogen loss in a purple soil sloping field in the Three Gorges Reservoir area and to provide references for fertilization management measures and non-point source pollution control in the reservoir area.Relying on the Three Gorges Reservoir Experimental Station of the Chengdu Institute of Mountains and Disasters of the Chinese Academy of Sciences,the experimental treatments included no fertilization(CK),conventional fertilization(F),optimum fertilization(OF),reduced fertilizer with biochar(BF),and reduced fertilizer with straw(SF)for three consecutive years from 2018 to 2020 to study the inter-annual variation characteristics of nitrogen loss in the purple soil sloping field under the rape-maize rotation model.The results showed that:①the surface runoff of the purple soil sloping field in the Three Gorges Reservoir area mainly occurred from May to August,and the subsurface flow mainly occurred from June to October.From 2018 to 2020,rainfall increased yearly,the surface runoff flow of each treatment decreased yearly,and the flow of abortion in the soil generally increased yearly.On the annual scale,the subsurface flow in the soil and the number of runoffs were higher than that of the surface runoff.②From 2018 to 2020,the highest loss concentration of various forms of nitrogen appeared simultaneously.The highest loss concentrations of total nitrogen,ammonium nitrogen,and nitrate nitrogen in surface runoff appeared in May,August to October,and July,respectively.The highest concentration of nitrogen loss of various forms of subsurface flow appeared in October,October,and May to July,respectively.③The loss flux of various forms of nitrogen in surface runoff showed a decreasing trend annually,and the loss of various forms of nitrogen in subsurface flow roughly increased annually.④Biochar and straw returned to the field were more effective in reducing the nitrogen loss flux in the first year;conversely,returning to the field in the following two years increased the nitrogen loss flux.Therefore,when fertilizing purple soil sloping land in the Three Gorges Reservoir area,it is necessary to consider the rainfall concentration characteristics of the area,strengthen fertilizer management during the period of nitrogen loss risk(May to October),and fertilize in different periods.It is also important to take effective interception measures when returning straw to the field to control nutrient loss and agricultural non-point source pollution.