Forms of Aluminium in Soils of East Khasi Hills, Meghalaya

Soil samples collected from different altitudes (100—1900m above m.s.l.) and topo-sequence of East Khasi Hills of Meghalaya were analysed for water soluble, exchangeable Al as well as that bound to organic and amorphous soil constituents and total aluminium. The amounts of all the forms of Al, except the total, were greater in soils of higher altitudes than those in the lower ones. Exchangeable Al occupied 0.4 to 40.3% of the cation exchange capacity. Al extracted with IN KCl became almost constant after 24 h contact with soil. In general, Al bound to organic and amorphous constituents were more in soils of higher altitudes. Soil pH was negatively and significantly correlated with water soluble, exchangeable, KCl extractable Al forms and also with per cent aluminium saturation. Al bound to organic amorphous soil constituents are correlated positively with soil organic carbon.