Nutrient fluxes in the Shenchong Basin, Deqing County, South China

In the severely eroded granitic areas of south China, the hillslopes are the source areas of, and the valleys are the sinks for, nutrients, water and sediments. Overall, the amount of nutrient loss is limited, since the nutrient pool in the upland soils is small. Nutrient losses are generally higher on cultivated fields than on barren or wooded slopes. A substantial proportion of the nutrients is transported in the solid phase. Because of the selective process of deposition with regard to particle size, nutrients are relatively more enriched in the soils and around the wetlands than on the alluvial fans. Soils developed on the alluvial fans are highly acidic and deficient in available nitrogen and phosphorus. The hydrochemical environment in the wetlands favours the dissolution of iron-bearing clay minerals in the subsurface water. High levels of iron and acidity may complex nutrients present in the soil and inhibit plant growth. Agricultural activities in the area thus require revegetation of the hillslopes and soil amelioration in the lowlands through fertilizer application and soil structure improvement.