密云县密云水库流域坡耕地养分流失特征

于2005年和2006年连续2 a对密云水库流域坡耕地进行水土流失小区试验,并完全按照当地农民习惯进行农事管理.试验结果表明:(1)降雨后坡耕地产生的地表径流量、泥沙量随坡度增大而增加,并与坡度正弦值呈一定的线性关系;(2)坡度对雨后地表径流和泥沙中养分含量影响不明显,但对泥沙养分流失量有明显影响;(3)养分流失以泥沙携带为主要途径,且通过泥沙携带途径流失的养分量占流失养分总量的比例随坡度增加而增加;(4)水库周边区域内坡耕地流失养分的主要来源为施用于坡耕地的化学肥料.(5)调整水库流域内坡耕地的种植结构、对坡耕地实施改造以截留或减少泥沙流失和控制化学肥料投入等措施对于治理流域内农业非点源污染、保护水源地水质显得尤为迫切.

Characteristics of Nutrient Loss From Sloping Fields in Miyun Reservior Watershed

Transport of nitrogen and phosphorus from sloping crop fields to waterbody causes eutrophication and non-point source pollution of the waterbody.A two-year(2005-2006) field experiment was conducted to study characteristics of nutrient loss from sloping fields in the Miyun Reservior watershed.The fields were managed in the same way as the local farmers do.Results of the experiment show that 1) the amounts of runoff and sediments therein from the sloping fields increased with the gradient of slope after rainfall,demonstrating a linear correlation;2) slope gradient did not show much effect on nutrient content of both runoff and sediments,but much on amount of nutrient lost with sediments;3) more nutrient lost with sediments than with runoff,and the proportion of nutrient lost with sediments versus total nutrient loss increased with slope gradient;4) the N,P lost from sloping fields were mainly originated from the chemical fertilizers applied by farmers;5) to control non-point source pollution and protect water quality of the water source,it is especially urgent to readjust the agricultural structure of the region,rebuild crop fields to intercept or reduce soil loss and control input of chemical fertilizers.