Effect of Continuous Cropping of Cassava with Organics and Inorganics on the Secondary and Micronutrient Elements Status of an Ultisol

Long term application of fertilizers and manures to cassava (tapioca) on an acid Ultisol decreased exchangeable calcium and magnesium in the soil. The decrease was not much marked in plots receiving superphosphate. Application of wood ash increased significantly the level of the above two cations. Foliar deficiency symptoms of calcium and magnesium appearedfrom the 10th year onwards. especially in the plots receiving Nand NK treatments. The available Zn and Cu of the soils declined under continuous cropping of cassava with fertilizer nutrients alone whereas inclusion of FYM had the reverse effect. Visual foliar symptoms of zinc was noted in N and NP treatments. Copper deficiency symptoms did not appear at any stage of the crop growth in spite of the decreased availability of Cu in soil.