模拟降雨条件下垄沟坡度对溶解态氮磷流失的影响

为揭示不同垄沟坡度对径流中溶解态氮、磷流失的影响,采用人工模拟降雨试验,设置4个垄沟坡度处理(0°,9°,18°和27°),研究了不同垄沟坡度对径流中速效磷(PO_4~(3-)—P)、硝态氮(NO_3~-—N)和铵态氮(NH_4~+—N)浓度和流失量的影响;并利用Inorganic—N/PO_4~(3-)—P、NO_3~-—N/PO_4~(3-)—P和NH_4~+—N/PO_4~(3-)—P 3种氮磷比,评价不同处理的富营养化风险。结果表明:(1)在降雨过程中,4个垄沟坡度处理径流中PO_4~(3-)—P、NO_3~-—N和NH_4~+—N浓度随时间均呈锯齿状变化;其流失量随时间变化均呈先增加后以锯齿状变化的趋势,且波动幅度大,最大值(16.60,1 020.73,48.35 mg)分别出现在垄沟坡度为0°,0°和9°处理。(2)4个垄沟坡度处理间相比较,径流中PO_4~(3-)—P和NH_4~+—N流失量均表现为0°9°27°18°,其浓度最大值(0.50,1.08 mg/L)和最小值(0.37,0.76 mg/L)均分别出现在垄沟坡度为9°和18°处理;而径流中NO_3~-—N浓度和流失量均在垄沟坡度0°处理时为最大值(30.68 mg/L和64.16 mg/m~2),18°处理时为最小值(21.78 mg/L和42.22 mg/m~2)。(3)Inorganic—N/PO_4~(3-)—P率和NH_4~+—N/PO_4~(3-)—P率表明4个垄沟坡度处理径流中均存在一定的富营养化风险。其中,垄沟坡度为0°处理的径流富营养化风险水平最高,27°处理的径流富营养化风险水平最低。研究结果可为横坡垄作的水土流失及养分流失评价、预测以及防治提供科学依据。

Impact of Furrow Slopes on Losses of Dissolved Nitrogen and Phosphorus Under Simulated Rainfall

This study explored the effects of four furrow slopes (0°, 9°, 18° and 27°) on the concentrations and losses of PO₄^3--P, NO₃^--N and NH₄⁺-N through simulated rainfall experiments, and evaluated eutrophication risk of the runoff by the ratios of Inorganic-N/PO₄^3--P, NH₄⁺-N/PO₄^3--P, and NH₄⁺-N/PO₄^3--P. The results were as follow:(1) PO₄^3--P, NO₃^--N, and NH₄⁺-N concentrations changed in the shape of wavy serrated shape with rainfall time under four furrow slopes. As for losses, their maximum value (16.60, 1 020.73, 48.35 mg) appeared in 0°, 0°, and 9° when they increased firstly and then changed in zigzag shape with rainfall time. (2) Under different furrow slopes, PO₄^3--P and NH₄⁺-N losses in runoff water were in order of 0° > 9° > 27° > 18°, whose concentration maximum value (0.50, 1.08 mg/L) and minimum value (0.37, 0.76 mg/L) appeared in 9° and 18°. NH₄⁺-N concentration and losses maximum value (30.68 mg/L and 64.16 mg/m²) and minimum value (21.78 mg/L and 42.22 mg/m²) appeared in 0° and 18° in runoff water. (3) The ratios of Inorganic-N/PO₄^3--P and NH₄⁺-N/PO₄^3--P showed that four furrow slopes output runoff all had eutrophication risk, and the 0° output runoff of that was the highest and the 27° was the lowest. These findings would provide scientific guidance for evaluation, prediction, and control of soil and water loss and nutrient loss in contour ridge system.