Abstract

Potassium (K) release characteristics (PRC) of soil play a significant role in supplying available K. Information about PRC in the Western Ghats acid soils is limited. The objective of this research was to study the PRC in 20 soils collected from the western Ghats area of Karnataka under paddy land use cover by successive extraction with 0.01 M CaCl2 over a period of 24 to 336 h. The physico-chemical properties, nutrients status and desorption of potassium were also studied. The release of K was initially rapid, more than 60% of the total K released during the first 120 h. The amount of cumulative potassium release of the soils under study ranged from 368 to 475 mg K/kg. The total Step-K and constant rate-K (CR-K) contents in soils of hilly zone ranged from 292 to 461 mg K/kg and 1 to 8 mg K/kg, respectively. However, the cumulative desorption varied from 155.30 to 355.40 mg K/kg during the interval of 24 to 336 h time. The potassium desorption rate coefficient (kd) for exchangeable-K release was more in the initial stage (up to 120 h). The kd values ranged from 1.07 x 10−2 to 9.80 x 10−3. The potassium desorption rate coefficient values (kd) for non-exchangeable-K release (120–336 h) varied from 1.29 x 10−3 to 9.17 x 10−4. The result of this research showed that information obtained from K release study in laboratory and kinetic equation parameters could help to estimate the K supplying power of soil.