Forms of Silicon in Rice Soils of Kerala, India

Abstract

Aim: The plant-available silicon (PAS) content is highly influenced by different forms/fractions of silicon (Si) in which it exists in the soil. The solubility of these forms varies and affects the Si concentration in soil solution. Quantification of Si pools in soils is needed for a better understanding of biogeochemical processes that govern Si dynamics in soils, the magnitude of Si release, and Si-cycling between soil and plant systems. In this context, an attempt was made to elucidate the status and distribution of Si pools in major rice-growing soils of Kerala.
 Methodology: The soil samples were collected from five different locations representing the major rice growing tracts (Kuttand, Kole, Pokkali, sandy and lateritic soils) of Kerala, India. The processed soil samples were analyzed to estimate various physicochemical properties. Then, using standard procedure, different fractions of Si in these soils were estimated and their correlation with physico-chemical properties of soils were worked out.
 Results: The forms of Si estimated in these soils were mobile Si, adsorbed Si, organic Si, amorphous Si, and residual Si. The percentage distributions of Si pools in these soils were mainly in the order; of residual Si > amorphous Si > occluded Si > organic Si > mobile Si > adsorbed Si. Mobile and adsorbed Si were the smallest fractions and amorphous Si was the largest fraction in these soils.
 Conclusion: Mobile and occluded Si were found to be the major contributors of PAS in major rice soils of Kerala.