Secondary and micronutrient status of cassava growing soils of Kerala

Abstract

Among the tropical tuber crops, cassava is recognized as the secondary staple for Keralites. Researh work carried out so far clearly revealed the significance of balanced application of manures and fertilizers including secondary nutrientsviz., Mg and micronutrients viz., Zn and B in improving yield and quality of cassava tubers as well as maintaining soil productivity. But under farmers's field situation, either under or over application of nutrients is very common resulting in impoverishment of soil health as well as wastage of monetary resources. In order to address this problem to an extent, as a prelude to formulating fertilizer schedule for primary, secondary and micronutrients based on soil test data, a rapid appraisal of the soil nutrient status including the secondary and micronutrients of the nine major cassava growing districts of Kerala was undertaken. The study indicated poor availability of both Ca and Mg in these soils with soils of Palakkad having comparatively better Ca and Mg contents as 45 and 75% respectively of the surveyed area above their respective critical levels. But the status of all the four micronutrients viz., Fe, Cu, Mn and Zn was satisfactory. The soils in the surveyed districts were sufficient in micronutrients especially Fe, Cu and Mn. The soils of Ernakulam district were deficient in Zn where 60% of the surveyed area was having Zn status below its critical level. Considering the specific secondary and micronutrient requirement of cassava, the present study revealed that the soils of the surveyed districts had low to medium Ca, Mn and Zn, low to high Mg, medium Fe and medium to high Cu in the uplands and lowland soils