Potassium release and adsorption reactions in two ferruginous (polygenetic) soils of southern India in relation to their mineralogy.
1993
Pal D.K. | Deshpande S.B. | Durge S.L.
In view of anomalous crop response to K-fertilizer treatment and for the lack of precise information on K release and adsorption reactions in ferruginous soils of southern India, the present experimental study on two such soils (Udic Rhodustalfs) was undertaken to pinpoint the role of nature and composition of soil minerals in these reactions of soils. Due to their polygenetic history the layer silicates of diverse chemical nature coexist in the different particle size fractions of the soils. As a result, the trend of K release following the repeated batch type Ba-K exchange from mica particles and the selective adsorption of K by smectite was not in full accordance with those hitherto obtained either with soil or specimen minerals. The K release from clay mica increased with the decrease in particle size while from silt mica a reverse trend was observed. Silt mica was comparatively unweathered as per XRD and SEM analyses, and it has more number of elementary layers. Thus the K release of silt mica is similar to the specimen mica. The observed selective adsorption of K by smectite, a fact in contrast to the behaviour of dioctahedral smectite of the soil clays, is however due to the presence of high charge trioctahedral smectite, an alteration product of biotite in semi-arid climate. The relevance of this study has been discussed in the context of K management in polygenetic ferruginous soils.
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