Potassium Fixation Characteristics and Fertilizer K Requirements of IIlitic Alluvial Soils by Two-step Alternate Methods

Potassium fixation characteristics and fertilizer K requirements of illitic soils were studied by two-step alternate method including equilibration for two hours and for two months. Increasing rates of added K increased the exchangeable K levels of soils. Safls high in initial K maintained higher exchangeable K even with further K additions. Longer time of equilibration (2 months) reduced the exchangeable. K at different rates of added K over two hours of equilibration. Soils low in K, fixed 80 per cent of added K within two hours of equilibration and with increased time of equilibration (2 months), increase in K fixation was low. Soils rich in K, fixed lower amounts of added K in two hours and in two months of equilibration showed substantial increase in K fixation over two hours of equilibration. Unit fertilizer requirement for unit increase in available K was more in low K soils. These requirements were further increased in two months equilibration. Regression analysis showed that there was 19 per cent reduction in exchangeable K in two months of equilibration over two hours of equilibration.