Phosphorus status of agricultural soils in northern and central Viet Nam

Abstract

Phosphorus status was assessed for the surface layers of 13 agricultural soils collected at locations differing in the parent rock, landform, and land use, in northern and central Viet Nam. Total P concentration ranged from 251 to 1,334 mg kg-1 and was most highly and significantly correlated with the organic P concentration. Percentage of organic P in total P varied considerably with the soils from 11 to 70%. Phosphorus availability was generally high for the soils derived from alluvium and sandstone and used as paddy soils, whereas the soils derived from limestone and basalt and used for upland crop cultivation were deficient in available P. Gradual change of nonoccluded Ca- and Al-bound P to nonoccluded Fe-bound P or occluded P with the progression of mineral weathering was suggested. The sediments from a river flowing through the densely populated and industrialized area in Ha Noi City contained very large amounts of total P and the major part was in an inorganic form.