Availability of Manganese in some Indian Soils growing Sugarcane

Manganese was determined in some soils by extracting with ammonium dihydrogen phosphate (available) and ammonium acetate (exchangeable). The efficiency of Aspergillus niger (M) in extracting soil manganese was also compared with other methods. Neutral soils showed a greater availability of manganese than those of higher pH. Generally loamy soils with pH near neutrality contained more of available and exchangeable Mn than heavy clay ones with pH more than 8.1. NH₄H₂PO₄ extracted more manganese than NH₄-acetate in all soils. Aspergillus niger method showed nearly the same amount of Mn as NH₄H₂PO₄ in soils of high pH but much less in loamy soils with neutral reaction. A. niger extracted as much or even more from subsoils than from surface layers and more efficiently than NH₄-acetate. All the soils contained manganese (NH₄H₂PO₄ extractable) above 20 ppm. Significant amounts of available manganese were observed below 15cm depth.