Author(s):

Harsha BR and Jagadeesh BR

Abstract: Potassium in soil can be allocated to three pools of availability for uptake by roots. It is dissolved in soil water, adsorbed onto particles of clay and organic matter and held within the crystal structures of feldspar and mica. These forms such as water soluble, exchangeable, non-exchangeable and lattice potassium were studied in twenty representative randomly collected maize growing soils of Haveri district, Karnataka, India. The soils varied appreciably in their physico-chemical properties depending on nature and amount of parent material. The available potassium in red soils varied from 268.80 to 483.84 kg ha^-1. The available potassium was medium to high in status. The variation in K status was due to cultural practices, application of fertilizers, organic manures and other inputs. The water soluble potassium in selected red soils of maize growing areas of Haveri district varied from 1.66 to 4.69 mg kg^-1 with a mean of 2.91 mg kg^-1. The reason for this was due to addition of water soluble potash fertilizers at surface zone. The exchangeable potassium content of red soils ranged from 44.80 to 78.40 mg kg^-1 in surface layer. The exchangeable potassium in surface layer was high because of high exchange sites offered for K fertilization and also addition of organic manures which might have enhanced the exchangeable K in solution phase. The non-exchangeable potassium of red soils ranged from 495.88 to 653.66 mg kg^-1 in surface. The increase in non-exchangeable potassium was due to adsorption and fixation of K removed from surface through leaching. The lattice potassium of red soils varied from 0.92 to 1.28 per cent. The total potassium in surface depth of red soils varied from 0.97 to 1.35 per cent. Based on degree of weathering and amount of fertilizer that has been applied, the various forms of potassium varied among the samples.

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