Abstract

Distribution of different forms of zinc in seven profiles of base unsaturated soils of Karnataka and their relation to soil characters were studied. The results showed that more than 82.7 per cent of total zinc occurred as residual zinc, whereas exchangeable zine occurred only 1.1 per cent of total zine content. Soils contained exchangeable Zn from 0.04 to 2.3 µg g', organically bound Zn from 0.07 to 6.44 ug g', manganese oxide bound from 0.1 to 4.3 ug gl amorphous iron oxide bound Zn from 0.5 to 7.7 Hg g, crystalline iron oxide bound from 0.5 to 8.2 µg g', residual zinc from 9 to 109 ug g'. Although the exchangeable pool was very low in all the soils when compared to other fractions, still it is very important from the plant availability point of view. Amorphous iron oxide bound form of zinc is the seat for zinc adsorption because of its high specific surface area. Crystalline iron oxide bound form of zinc dominated when compared to exchangeable, organically bound, manganese oxide bound and amorphous iron oxide bound zinc fractions.

Keywords: Zinc fractions, Exchangeable, Organically bound, Manganese oxide bound, Amorphous and crystalline oxide bound, Residual, Total zinc.