STUDIES ON SILICON POOLS IN RICE SOILS OF SELECTED AGRO CLIMATIC ZONES OF KARNATAKA
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Date
2017-09-28
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
In order to study the different pools of Si in soils and their contribution to rice,
two surface soil samples were collected from each of four agro climatic zones of
Karnataka with distinct climatic features. Five major pools of silicon (Si) such as mobile
Si, adsorbed Si, organic matter bound Si, occluded Si in pedogenic oxides/hydroxides and
amorphous Si were extracted from these soils using a sequential extraction method. The
different pools of Si extracted from soils were in the order of amorphous Si > occluded Si
> organic Si > adsorbed Si and mobile Si. The mobile Si and adsorbed Si pools were the
smallest pools of Si and ranged from 14.45 to 44.60 mg kg-1 and 4.90 to 89.40 mg kg-1
,
respectively. Irrespective of the soils, amorphous Si was found to be the largest pool of Si
ranging from 8,019 to 16,667 mg kg-1. Pot culture experiment conducted using the bulk
soil samples of these zones with rice as test crop revealed that there was a significantly
higher Si content and uptake in Bellatha (southern dry zone) and Honnavile soil (southern
transition zone), respectively and lower in Brahmavara soil (coastal zone). Better
correlation and regression coefficients were recorded between Si pools, plant available Si
in soils and Si content and its uptake by rice when only three soils (one each from low,
medium and high content of plant available Si) were considered among the eight selected
soils. The occluded, mobile and adsorbed pools of Si showed significantly higher
correlation and regression with Si content and its uptake by rice and hence considered as
major contributors of Si to rice.
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