Influence of soil texture on potassium availability, fixation and uptake by rice in laterite soils

Abstract

The present investigation was carried out m order to assess the influence of various proportions of clay on the potassium dynamics in s oil on application o f potassium fertiliser and its effect on the uptake o f nutrients by rice Sixty surface samples were collected from the major rice growing areas of Thrissur district Based on their particle size analysis and organic carbon content, twenty samples were selected for studying the various physico-chemical characteristics related to the potassium availability In order to find out the transformations of applied potassium, a laboratory incubation experiment was carried out in five selected soils for a period of three months Mineralogy of the fine sand fraction was also carried out in these soils A pot culture experiment was carried out in four selected soils to determine the uptake of nutrients. The soils collected from the three locations showed wide variations in their clay content and majority o f them were grouped under the textural classes, sandy loam and sandy clay loam The single value constants were showing variations depending on the clay content and organic carbon The content and uptake o f N, P, and K was found to increase with increasing levels o f K application Calcium did not show significant difference with applied K and in the case of Mg a decreasing trend was observed The water-soluble and ammonium acetate extractable K were decreasing with advancement o f the crop growth and these fractions were found to be maximum correlated with the dry matter weight at i the flowering and tillering stages respectively Nitric acid soluble fraction was found to contribute towards the later stages of crop growth Maximum correlation was obtained for the gram yield and straw yield with this fraction Even though the positive effect of potassium application on the yield of paddy is very conspicuous, the response varied with the textural composition In more clayey soils more o f potassium fertilisers hast to be recommended to get maximum response as revealed m the present study