In the severely eroded granitic areas of south China, the hillslopes a
re 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 slo
pes. A substantial proportion of the nutrients is transported in the s
olid 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 nitrog
en and phosphorus. The hydrochemical environment in the wetlands favou
rs the dissolution of iron-bearing clay minerals in the subsurface wat
er. High levels of iron and acidity may complex nutrients present in t
he soil and inhibit plant growth. Agricultural activities in the area
thus require revegetation of the hillslopes and soil amelioration in t
he lowlands through fertilizer application and soil structure improvem
ent.