Distribution of Different Forms of Potassium in Benchmark Soil Series under Rice-Wheat Cropping System in Punjab

摘要

Rice-wheat cropping system (RWCS)removes large quantity of potassium from soils leading to negative K balances.The present investigation was undertaken to estimate the distribution of different forms of K in major benchmark series under RWCS in Punjab.Two profiles were exposed from each of the four benchmark series viz.Gurdaspur,Naura,Ladowal and Nabha and one from Dhar series which extensively fall under RWCS,and samples were collected from different horizons.Fifty surface soil samples (0-15 cm)were also collected from different sites of these benchmark series.In surface soil samples,water soluble K was highest in Nabha followed by Ladowal,Naura,Gurdaspur and Dhar series.Available K and boiling nitric acid K contents were highest in Ladowal and lowest in Dhar and Gurdaspur series.Water soluble K and available K contents decreased with increasing soil depth in all the soil series.The 1M HNO_3 and total K contents did not show specific distribution trend with depth.Based on linear coefficient of correlation total,HNO_3 and available contents of K showed significant positive correlation with clay and silt contents.