Potassium Release Parameters and their Relation with Yield of Rice Based Cropping Systems in Bapatla District, India

An investigation was carried out to study the different potassium release parameters in rice based cropping systems (viz. Rice-Pulse, Rice-Groundnut, Rice-Maize and Rice-Sorghum cropping systems) of Bapatla district of Andhra Pradesh and their relation with rice yield and rice equivalent yield of different cropping systems. Step-K values in Rice-Pulse, Rice-Groundnut, Rice-Maize and Rice-Sorghum cropping systems was in the range of 505-1266, 414 -884, 742-1296 and 776-1369 mg kg-1 with the mean values of 954, 563, 965 and 1067 mg kg-1, respectively. Constant-K values in Rice-Pulse, Rice-Groundnut, Rice-Maize and Rice-Sorghum cropping systems was in the range of 17-28, 11-22, 17-25and 14-27mg kg-1 with the mean values of 23, 17, 21 and 20 mg kg-1, respectively. Cumulative-K values in Rice-Pulse, Rice-Groundnut, Rice-Maize and Rice-Sorghum cropping systems was in the range of 607-1466, 480-1038, 889-1496 and 930-1585 mg kg-1 with the mean values of 1119, 672, 1123 and 1223 mg kg-1, respectively. The highest potassium release parameters such as step-K and cumulative K observed in rice-sorghum cropping system and the lowest in rice-groundnut cropping system. Lower amounts of cumulative K were observed in all soils except in soils of Kodiparru and Ananthavaram villages under present investigation. Lower cumulative K and continuous cropping would lead to depletion of soil K reserves and result in K deficiency. Among the K release i.e cum- K and step K obtained with boiling 1N HNO3 showed maximum positive and significant correlation with rice yield and rice equivalent yield while, constant K showed minimum correlation.