Author(s):

Shivaprasad Patil, Jagadeesh BR and Patil PL

Abstract: Potassium fixation of soils is an important phenomenon affecting the status of soil K and its availability to crops. It is the process in which soils converting exchangeable or water soluble potassium to fixed form in the inter lattice position of clay minerals. Potassium releasing power refers to the inherent capacity of the soil to supply K to growing plant from its natural source. The present study was undertaken to know the potassium fixation and release characteristics in the surface and sub-surface samples of Kavalur sub-watershed of Koppal district. The K release characteristics of soils were determined by employing successive extraction of soil with boiling 1N HNO₃ and the potassium fixation was studied by taking representative samples from surface and subsurface soil. The results prevailed that the highest rate of potassium fixation was observed in the AWD (1.41 cmol (p⁺) kg^-1) soil series and lowest in the GRH (0.61 cmol (p⁺) kg^-1) soil series in surface soils whereas, in sub-surface soils highest rate of fixation capacity was observed in the AWD (1.44 cmol (p⁺) kg^-1) soil series and lowest in GRH (0. 64 cmol (p⁺) kg^-1) soil series. Sub-surface soil recorded highest fixation capacity compare to surface soil. The cumulative K release from different soil series ranged from 329 to 975 mg K kg^-1 in surface soils whereas, in sub-surface soils were ranged from 328 to 1012 mg K kg^-1. The constant rate potassium (CR-K) content of soils as influenced by long term soil fertility management were ranged from 4 to 24 mg K kg^-1 in the surface soils and 4 to 20 in sub-surface soils. Total step- K of surface soils ranged from 269 to 687 mg K kg^-1 whereas, in sub-surface soils ranged from 274 to 792 mg K kg^-1.

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