坡长和雨强对氮素流失影响的模拟降雨试验研究

为研究氮素的流失特征,探索坡长和降雨强度对氮素流失的影响,选定坡长(2,3,4,5m)和降雨雨强(0.65,0.69,0.83,0.85,1.01,1.20,1.37,1.54,1.68,1.80mm/min)作为可变因素,在红壤裸坡上进行室内人工模拟降雨试验。结果表明:(1)坡面径流中各形态氮素流失随时间推移基本趋势为降雨初期径流携带氮素的浓度大,随后氮素浓度下降,至20min左右下降趋势变缓,最终径流中同一形态氮素的浓度趋于一致。(2)坡长一定时,径流中各形态氮素的总流失量随降雨强度的增大而增大,呈现较为明显的正相关性。各场次降雨中,各形态氮素的总流失量均为5m坡长最大,2m坡长最小。(3)径流量与TN、NO_3~-—N的总流失量之间存在极为显著的相关性,而对NH_4~+—N的总流失量影响较小。(4)径流中TN、NO_3~-—N的流失量与坡长、雨强、径流量都达到了极显著相关水平,相关性依次为径流量雨强坡长,而径流中NH_4~+—N的流失量只与雨强显著相关。(5)坡长、雨强及径流量与径流中各形态氮素总流失量的综合影响分别可以用线性相关方程进行描述,显著性依次为TNNO_3~-—NNH4+—N。

Research on the Effect of Slope Length and Rainfall Intensity on Nitrogen Loss in Sloping Land Under Artificially Simulated Rainfall

Soil nitrogen loss caused by slope runoff is one of the important source of agricultural non-point source pollution.In order to investigate the effects of slope length (2 m,3 m,4 m and 5 m) and rainfall intensity (0.65 mm/min,0.69 mm/min,0.83 mm/min,0.85 mm/min,1.01 mm/min,1.20 mm/min,1.37 mm/min,1.54 mm/min,1.68 mm/min and 1.80 mm/min) on runoff producing processes and nitrogen loss,an artificially simulated rainfall experiment was conducted.The results showed that:(1) Under the condition of rainfall,the changing trends of different forms nitrogen concentration in runoff were high in the early stage,then decreased with increasing time,and slowed down at 20 min,and gradually became stable for the final rainfall,and in the end they tended to coincide;(2) Under the same slope length,the loss of different forms of nitrogen increased with increasing rainfall intensity,showing a significant positive correlation.In each rainfall events,the loss of different forms of nitrogen was always the maximal when the slope length was 5 m,and the minimal when the slope length was 2 m;(3) There were very significant correlations between runoff volume and total loss of TN and NO3--N,but the influence on NH4 +-N was weak;(4) The correlation between total loss of TN,NO3--N and slope length,rainfall intensity,runoff volume were very significant,and the significance of the correlation followed the order of runoff volume＞rainfall intensity＞slope length.However,the total loss of NH4+-N was significantly correlated with rainfall intensity only;(5) The influence of slope length,rainfall intensity or runoff volume on the total loss of different forms of nitrogen in the runoff could be described as linear correlation equations,and the significance level was in the order of TN＞NO3-N＞NH4+-N.