Studies on Potassium Releasing Pattern in Various Textural Types of Alluvial Soils of Assam by the Method of Exhaustive Cropping

The potassium intenstity values of three alluvial soils under exhaustive cropping with rye grass (Lolium perenne) decreased progressively during the initial cropping period, when dry matter yield, K uptake and K concentration in harvested material increased. Thereafter, the intensity values tended to increase to their original levels for a period when dry matter yield, K uptake and K concentration of harvests decreased gradually. During the later cropping period, these parameters declined slightly until soils reached exhaustion levels. The intensity values at the exhaustion levels were found to be nearly same for all the three soils. K intensity values were not significantly correlated with dry matter yield. The estimated uptake of nonexchangeable potassium during exhaustive cropping varied between 0.90 to 2.74 mg K/100 g soil, the lowest and highest uptake coinciding with the shortest and longest periods of cropping at which exhaustion signs were exhibited.