Soil potassium release as indices of potassium supplying power of coastal soils of West Bengal

An exhaustive pot experiment was conducted to assess the potassium supplying power of four coastal soils of West Bengal by comparing the different test values of soil K indices estimated by different chemical extraction procedures with plant indices viz., total dry matter yield and plant K uptake. The soils having wide variations of physical and chemical properties and forms of K were subjected to intensive cropping with two cycles of a crop rotation consisting of three successive crops viz., paddy greengram -sunflower in two consecutive years. Results showed that plant dry matter yield and cumulative K uptake had highly significant positive correlations with available K (NH₄OAc-K), nonexchangeable K (HNO₃-K), step K, constant rate K (CR-K), cumulative release K, planar K (KO) and equilibrium activity ratio of K (AR_e^OK) and significant negative correlations with non-specific sites K and Gibb's free energy change. Based on the magnitude of the correlation coefficient values between soil K indices and plant indices, various soil K parameters were arranged in the sequence of KO > CR-K > cumulative K release > AR_e^OK > NH₄OAc-K > step K > HNO₃-K. These suggest that any of the soil K parameters might serve as a good index of long-term K supplying power of the coastal soils.