Abstract:In the karst area of the Danjiangkou reservoir area, the nitrogen (N), phosphorus (P) and potassium (K) nutrient loss and the sediment particle size distribution characteristics of slope erosion in five vegetation cover types (arbor forest land (C1), sparse forest land (C2), farmland (C3), grassland (C4), shrub grassland (C5)) under natural rainfall conditions were observed to discuss the relationship between sediment nutrient loss and particle size distribution. The results showed that:(1) The sediment of erosion was dominated by silt (2~50 μm) and sand (50~2 000 μm). There were significant differences in the sorting of clay (0~2 μm) particles between different vegetation cover types (P<0.05). The contents of fine particles (0~20 μm) in the eroded sediment decreased with the increase of rainfall intensities. The 0~2 μm particle concentrations were concentrated in 3.08~6.62. The 2~20 μm particle concentrations were concentrated in 2.48~3.58. The 20~50 μm particle concentrations were concentrated in 1.04~1.62. The 50~100 μm particle concentrations were concentrated in 0.61~0.88. The 100~2 000 μm particle concentrations were concentrated in 0.43~1.15. The 0~20 μm particle enrichment of C4 was the largest, and the 0~20 μm particle enrichment of C3 was relatively small. (2) Among the available nutrients, the loss of available K (AK) was much higher than those of available N (AN) and P (AP). The concentrations of total P (TP) and AK of C4 were significantly higher than those of C1, C2, C3 and C5 (P<0.05). The total nutrients loss in C3 was the largest, and C1, C2, C4 and C5 had the significant effect on reducing nutrient loss. The effect of C2 on controlling nutrient loss was the most obvious. The total N (TN) concentrations were concentrated at 0.56~1.25, the NH4+-N at 1.08~1.17, the NO3--N at 0.94~1.50, and the TP at 1.41~1.96, the AP at 5.00~8.77, the AK at 1.79~3.05. The N and P enrichment were relatively low in C3, and relatively large in C2 and C4. (3) The contents of TN, TP, AP and AK in erosion sediment were positively correlated with the contents of 0~2, 2~20 and 20~50 μm, and the correlation with 0~2 μm was significant (P<0.05). The nutrient concentrations increased as the fine particle content increased.