BIOGEOCHEMISTRY OF SILICON IN DIFFERENT RICE ECOSYSTEMS OF KARNATAKA
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Date
29-12-12
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
In order to understand biogeochemistry of silicon (Si), plant available Si
(PAS) content was analysed in soils of different agro climatic zones of Karnataka
besides conducting pot and field experiments to know the efficacy of different sources
of Si and its bioavailability in rice ecosystem. Plant available Si content ranged from
1.41-82.89 mg kg-1 as extracted by calcium chloride (CCSi) and 6.69-370.24 mg kg-1
as extracted by acetic acid (AASi). Pearson’s correlation coefficient worked out for
soil analytical data revealed a significant positive correlation between PAS and soil
pH, silt, clay, cation exchange capacity and negative correlation with sand content. XRay
Diffraction analysis of the soil samples revealed the presence of quartz, feldspars,
amphibole, phyllosilicates as primary minerals and smectite, kaolinite, illite,
vermiculite as clay minerals in various proportions. AASi was positively correlated
with Al2O3, Fe2O3, MnO and TiO2 demonstrating the extractant assessed the fraction
of Si adsorbed on the surface of oxides or oxy-hydroxides and clays while, CCSi for
immediate dissolved Si. Application of diatomite @ 300 kg ha-1 significantly
increased the grain yield and numerical increase in other yield attributes in the field
experiment. Budgeting of Si in a rice ecosystem revealed that majority of the
biogeochemical cycle of Si was controlled by uptake, dissolution and contribution by
irrigation water. Bioavailability of Si for rice in acidic, neutral and alkaline soil
revealed that application of calcium silicate, diatomite and rice husk biochar
significantly increased the yield parameters. Higher Si uptake was noticed in neutral
soil followed by acidic and alkaline soil. In acidic and neutral soil, application of
calcium silicate significantly increased the nutrient status of soil whereas rice husk
biochar in alkaline soil and justifies the variability in reactivity of the sources in
different soils rather than total Si content.
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