TRANSFORMATIONS IN PLANT-AVAILABLE FORMS OF IRON AND MANGANESE AS INFLUENCED BY MANURING AND CROPPING UNDER IRRIGATION

Vertisols from field plots fertilized continuously with P, K, FYM [farmyard manure] alone and in combination at the rate of 60 kg P2O5, 30 kg K2O and 1.5 ton FYM/ha were tested for different forms of Fe and Mn as a consequence of continuous cropping with sorghum and wheat. The transformations that occurred in different forms of plant-available Fe were greater than those of Mn. Exchangeable and easily reducible Fe contents were markedly influenced by treatments. In Mn, transformations of easily reducible to exchangeable forms were conspicuous.