Fractions of Phosphorus from Some Acid Hill Soils of North-West India

Phosphorus fractions of the surface layers of some acid hill soils of north-west India revealed that these soils werefairly rich in total P reserve (average 493 ppm). The mineral, organic and residual P, on an average, constituted about 49.6, 46.6 and 33.6 per cent of total P.

The dominance of reductant soluble P in these soils is probably the cause of negligible or no responses to P application in rice crop under low lying situations. The relative sequence of P fractions indicated that majority of the soils amples (about 92%) were in advanced stage of weathering whereas the remaining were weakly weathered. Among soil properties only clay fraction significantly influenced the total P and Fe-P. As regards the role of different forms, of Al, Fe and Ca in the formation of inorganic P fractions; total and extractable Alwere significantly associated with the formation of Al-P whereas amorphous and total Fe explained the maximum variation in Fe-P fraction. Forms of Ca did not show any correlation with Ca-P fraction. However, the major variation in R-S-P was accounted for, by the variation in extractable and amorphous Fe.