STUDIES ON POTASSIUM DYNAMICS IN RICE SOILS OF DIFFERENT AGRO-CLIMATIC ZONES OF KARNATAKA
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Date
1999-08-30
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK BANGALORE
Abstract
An investigation was earned out to study the potassium dynaimics in rice soils of
diSerent agro-climatic zones of Kamataka, The soils used in the study varied widely in
then- characteristics.The water soluble, exchangeable and non-exchangeable K contents of
soils varied from 2 to 7, 31 to 232 and 60 to 982 ppm, respectively. While, lattice and
total K contenu varied from 0.297 to 2.818 and 0.306 to 2.876 per cent, respectively. On
an average, water soluble, exchangeable, non-exchangeable and lattice K constituted O.OZ
1.02 and 96.02 per cent of total K. Coarse sand and fine sand fractions were the dominant
contributors to total K in coarse textured soils while, silt and clay were the major
contributors to total K in fine textured soils. The cold H2SO4 extractabie K was found to
be a better availability index for these soils . The higher K releasing power was noticed in
soils of Belgaum, BhadravatlHiriyur and Kathalgere. The soils of hilly and coastal zones
exhibited poor K releasing power. The smectitic black soils showed higher K supplying
power than kaolinitic red and laieritic soils and a distinct difference between K releasing
power and K supplying power of soils was brought out in this study. Green house studies
indicated that the kaolinitic soils, particularly, soils of hilly and coastal zones would
respond well to application of K at higher level (50 ppm) whereas, the smectitic black
soils may need only maintenance dose (25 ppm) of potash fertilizer.The potassium fixation
capacity of soils raided from 0.16 to 1.53 c mol (p+ kg -1 the black soils showing
higher fixation capacity than red and lateritic soils. EEtc, the K bearing mineral was present
as an associated clay mineral in all the soils except in soils of Bhadravati and Hiriyur where,
it occurred as co-dominant mineral along with Kaolinite.
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