中文摘要：

通过对川中丘陵不同施肥试验田径流、泥沙和磷素流失的观测与测定分析，研究了暴雨下平衡施肥对紫色土坡耕地水土流失与土壤磷素随径流流失的特征。结果表明：相对于无肥区和单施氮肥区，平衡施肥试验田的泥沙量减少了60％-65％，径流量减少了28％-33％，表现出显著的水土保持作用；在作物不同生育期，土壤磷素随地表径流迁移的强度依次为：成熟期〉拔节期〉抽雄期；暴雨下地表径流磷含量呈现先升高后下降的变化趋势；颗粒态磷是径流磷的主要组成部分，占总磷迁移量的54％-79％，说明泥沙吸附态迁移是紫色土坡耕地的主要迁移形式；不同施肥处理的径流磷损失存在显著差异，平衡施肥处理的总磷流失减少了52％-61％；径流量、泥沙量与径流磷迁移量显著线性相关；作物生长情况显著影响土壤磷素流失，地上部分生物量与径流磷流失量呈明显负相关。为了防止紫色土磷流失而加剧农业非点源污染，应在该区坚持以氮、磷、钾为主的平衡施肥。

英文摘要：

A field experiment was carried out in hilly area of central Siehuan Basin to study the characteristics of phosphorus loss by runoff from slope cropland in purple soil. There were 4 kinds of fertilization systems, no fertilizer （NF）, N alone （N）, N＋P （NP）, N＋P＋K （NPK）. Series water samples were collected from the different plots in each rainfall event, at the same time, flow of the surface runoff was also measured. Total phosphorus （TP）, dissolved phosphorus （DP） and particulate phosphorus （PP） were measured or calculated for the samples. The results showed as follows： compared with NF or N, the sediment yield of NP and NPK decreased by 60%-65%, the runoff decreased by 28%-33%, implying that balanced fertilization had significant effects on soil erosion. During various bearing stages of summer maize, there were obvious differences in the losses of phosphorus by runoff, with the order of maturing stage〉jointing stage〉tasseling stage. The contents of phosphorus rose in the beginning of runoff, and then decreased gradually. 54%-79% of total phosphorus were particulate phosphorus which was the major form of phosphorus loss in runoff. There were significant differences in the losses of total phosphorus under various fertilization systems, and 52%-61% of the phosphorus loss could be prevented by balanced fertilization, but there were no significant differences in the loss of dissolved phosphorous. The loss of phosphorus was positively linear correlated with the runoff or sediment yield. The biological properties significantly affected the loss of phosphorus, and there was a negative correlation between loss of phosphorus and the aboveground biomass. In order to control agrieuhural non-point source pollution, balanced fertilization should be popularized in this area.