坡面径流携氮素流失的多要素影响效应研究

Research on multi-factor effect of nitrogen loss in slope runoff

为研究坡面氮素的流失特征,探索植被覆盖度、坡长和不同施肥处理对全氮(TN)、硝态氮(NO_3^--N)、铵态氮(NH_4^+-N)流失的影响,选定不同植被覆盖度(0%,15%,30%,45%,60%,75%,90%)、不同坡长(3,4,5 m)和不同施肥处理(空白(CK),无机复合肥(CF))作为可变因素,在红壤坡面上进行室内人工模拟降雨试验。结果表明:随着植被覆盖度的增大,不同坡长坡面径流中各形态氮素的平均流失浓度均大致呈现上升趋势,不同坡长间各形态氮素平均流失浓度的总体规律为5 m> 3 m> 4 m。TN和NO_3^--N的总流失量随着植被覆盖度的增大而减少,而NH_4^+-N的总流失量没有明显变化规律。在等坡长差的情况下,5 m与4 m坡长间的各形态氮素流失量的增幅大于4 m与3 m间的。径流中氮素的流失以可溶态氮为主,而NO_3^--N是径流中氮素流失的主要形态。施用无机复合肥会使径流中各形态氮素的总流失量明显提高,其中NO_3^--N流失量占TN流失量的比例上升,NH_4^+-N比例下降。径流中各形态氮素的总流失量与植被覆盖度、坡长都达到了极显著相关水平,总体来说是NO_3^--N> TN> NH_4^+-N、植被覆盖度>坡长。植被覆盖度和坡长对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TN> NO_3^--N> NH_4^+-N。

In order to investigate effects of under different vegetation coverage( 0%,15%,30%,45%,60%,75%,90%),slope lengths( 3 m,4 m,5 m) and fertilizer treatments( control( CK) and compound N-P-K fertilizer( CF)) on runoff producing processes and nitrogen loss,an artificial simulated rainfall experiment was conducted. The results showed that: With the increasing of vegetation coverage,the average loss concentrations of different forms nitrogen on different length slopes were generally increasing,and the general law of average concentrations on different length slopes was 5 m > 3 m > 4 m. The total loss of TN and NO3--N were reduced with the increasing of vegetation cover,but the law of NH4+-N was not obvious. In the case of equal slope length difference,the increase of nitrogen loss between 5 m and 4 m slope is more than 4 m and 3 m. The loss of nitrogen in runoff was dominated by soluble nitrogen,while NO3--N was the main form of nitrogen loss in runoff. The total loss of TN,NO3--N and NH4+-N in runoff was significantly increased by the application of inorganic compound fertilizer,which would increase the proportion of NO3--N to TN in runoff and decrease the ratio of NH4+-N as well.The correlation between total loss of different forms nitrogen and vegetation coverage,slope length were very significant,and the correlation followed as: NO3--N > TN > NH4+-N,vegetation coverage > slope length. The influence of vegetation coverage,slope length to the total loss of different forms nitrogen in runoff could be described as linear correlation equations,and the significance level were,in order,TN > NO3--N > NH4+-N.