烤烟坡耕地壤中流氮、磷浓度的动态特征

选取我国西南部抚仙湖流域典型小流域——尖山河流域为试验区,以流域主要土地利用类型——烤烟坡耕地土壤为研究对象,在天然降雨条件下,原位监测了作物整个生长期,坡耕地土壤不同坡位壤中流（0～2 m）中磷、氮的浓度垂直分布特征及其时间动态变化规律。结果表明,不同坡位各层壤中流总氮（TN）和总磷（TP）浓度变化趋势基本一致,但不同坡位壤中流中TP浓度随深度的变化呈波动递减规律,随深度的增加变异系数变小。坡位对0~50 cm的壤中流氮、磷浓度影响最大,坡下部明显大于坡中部。翻耕导致各层壤中流氮、磷浓度差异显著增大。各层氮、磷浓度与降雨量呈负相关。在2 m深处TN和TP浓度的平均值分别为6.371mg.L-1和0.024 mg.L-1,超出相邻水体（抚仙湖）中氮、磷浓度的控制要求。这一结果表明,尖山河流域土壤表层中的氮、磷含量较高,丰富的降雨-壤中流过程极易推动土壤氮、磷传输。因此,除了地表径流传输控制外,如何有效抑制壤中流中的氮、磷迁移对该区域水环境污染的治理十分关键。

Dynamics of Nitrogen and Phosphorus in Tobacco Slope Cropland Interflow

An experiment was conducted on a slope cropland in Jianshan River basin,a typical catchment in the area of Fuxian Lake,southwest China to study the vertical distribution and the movement of nitrogen and phosphorus within the soil layer 0~2 m during the tobacco growing season under the condition of rainfall.The results showed that the variation of TN and TP content at soil layers interflow in different slope posi-tion was not big.But the interflow TP concentration declined fluctuantly and the coefficient of variation became smaller as the depth increasing in different slope positions.The TN and TP content of interflow within 0~50 cm were affected mostly by slope position,which were low at the middle part slope land,enriched at lower part slope land.The farmer ploughs soil up had nitrogen and phosphorus content been different at soil layers interflow.Also,the concentration of nitrogen and phosphorus of interflow was negatively correlated with rainfall.The average concentra-tions of TN and TP at the depth of 2 m were 6.371 mg.L-1 and 0.024 mg.L-1,respectively,which was beyond the control requirements to dis-charge nitrogen and phosphorus into adjacent water body of Fuxian Lack.The studies showed that there were rich nutrients of N and P in the surface soil at Jianshan catchment.The process of soil interflow through the rainfall promoted the translocation of N and P.How to control the moving of N and P of interflow,besides the control of runoff,might be an efficient way for maintaining the water quality of Fuxian Lake.