自然降雨下蔬菜地土壤侵蚀及氮素流失特征

Characteristics of Soil Erosion and Nitrogen Loss in Vegetable Field Under Natural Rainfall

为探究自然降雨下露天蔬菜地土壤侵蚀及氮素养分流失特征,基于径流小区原位观测试验,设置叶菜类和果菜类这2种处理,测定次降雨下不同类型蔬菜地坡面地表径流、侵蚀及其氮素(铵态氮和硝态氮)流失量,探讨露天蔬菜种植坡面土壤侵蚀及氮素流失特征及影响因素.结果表明:(1)果菜类(茄子-辣椒)蔬菜地的地表径流、侵蚀量及铵态氮、硝态氮流失量显著高于叶菜类(油麦菜-红薯叶),是后者的1.27~2.00倍.不同处理下第二季蔬菜坡面地表径流、侵蚀及其铵态氮和硝态氮流失占总流失量的50.86%~68.83%,是第一季蔬菜的1.03~2.04倍.蔬菜地坡面地表径流、侵蚀及其氮素流失集中在6月和7月,地表径流和侵蚀泥沙中氮素主要以地表径流中的硝态氮形式流失.(2)次降雨下,不同处理蔬菜地坡面地表径流、侵蚀及其养分流失在蔬菜生长期内呈波动变化,且流失量主要集中在几场典型降雨.整体上不同处理下第一季蔬菜地表径流和侵蚀泥沙中硝态氮和铵态氮流失量及含量低于第二季蔬菜,果菜类地表径流、侵蚀量及铵态氮、硝态氮流失量高于叶菜类.(3)蔬菜地坡面地表径流、侵蚀及其铵态氮和硝态氮流失量与降雨量和最大30 min降雨强度等降雨参数呈极显著正相关关系.大雨降雨等级是引起蔬菜地土壤侵蚀及其铵态氮和硝态氮养分流失的主要降雨等级,其次是暴雨和中雨,分别贡献了29.58%~46.68%、24.54%~36.79%和24.01%~39.13%的流失量,且不同蔬菜处理坡面地表径流、侵蚀与铵态氮和硝态氮流失对降雨等级的响应存在明显不同.研究结果有助于明晰南方露天蔬菜地土壤侵蚀及养分流失规律.

The effects of vegetable planting on soil loss and nutrient loss,runoff,soil erosion,and nitrogen(ammonium nitrogen and nitrate nitrogen)losses under individual rainfalls of fruit-and leaf-vegetable fields between April to October in 2021 were observed using in-situ observation testing.The results showed that:(1)the runoff,erosion,and nitrogen loss of the fruit-vegetable pattern(eggplant-chili)were 1.27-2.00 times those under the leaf-vegetable pattern(leaf lettuce-sweet potato leaves),especially under the second season vegetable period.Those losses under the second season vegetable accounted for 50.86%-68.83%of the total losses under different vegetable patterns,which were approximately 1.03-2.04 times those under the first season vegetable.The runoff,erosion,and nutrient loss of vegetable fields under different treatments were both concentrated in June and July,and the nitrogen loss was mainly in the form of nitrate nitrogen with surface runoff.(2)The runoff,erosion,and nutrient losses under individual rainfalls of vegetable fields under different treatments fluctuated among the vegetable growing season,and the losses were mainly concentrated in several typical rainfall events.On the whole,the loss and concentration of nitrate and ammonium nitrogen in runoff and erosion sediment of vegetables in the first season were lower than those in the second season.The runoff,erosion,and loss of ammonium nitrogen and nitrate nitrogen of fruit-vegetable were higher than those of leaf-vegetable.(3)Both rainfall amount and maximum 30 min rainfall intensity had significantly positive effects on runoff,soil loss,and nitrogen loss.Runoff,erosion,and nutrient losses under different vegetable patterns were mainly generated by moderate rain,heavy rain,and heavy rainstorms,which accounted for 29.58%-46.68%,24.54%-36.79%,and 24.01%-39.13%of the total losses,respectively.The results also showed that soil erosion and nutrient losses generated by different rainfall grades were obviously different for the fruit-and leaf-vegetable treatments.The results indicated that the vegetable pattern had significant impacts on soil loss and nutrient loss,and the leaf-vegetable pattern could reduce soil erosion and nutrient loss compared with the fruit-vegetable pattern.Furthermore,for different vegetable patterns and vegetable growing seasons,the effects of rainfall on soil loss and nutrient loss were quite different.The results of this study were helpful in clarifying the soil erosion and nutrient loss characteristics of vegetable fields in South China.