Potassium Dynamics and Response to Applied Potassium in Paddy Paddy and Sunflower Bengalgram Cropping System Under Vertisols in TBP Command Area

Abstract

An investigation was carried out on one hundred and fifty surface and subsurface soil newlinesamples of dominant cropping system of TBP command area for physico-chemical and newlinemineralogical properties of the soils, quality and distribution of different forms of potassium, newlinepotassium reserves in textural fractions and its fixation. Field experiments were also newlineconducted to study the response of applied potassium in paddy-paddy and sunflowerbengalgram newlinesequence with farmer s participation. The soils are low in water soluble K, newlinemedium to high in exchangeable K, which ranged from 78 to 238 mg kg-1 in surface and from newline103 to 265 mg kg-1 in subsurface layers. The non exchangeable K varied between 342 to 602 newlinemg kg-1 and 374 to 631 mg kg-1 in surface and subsurface layers, respectively. The amount of newlinelattice K content in surface horizons varied from 2.90 g kg-1 to 9.88 g kg-1 and 3.25 to 11.0 g newlinekg-1 in subsurface layers of both the cropping sequence. The total content ranged between newline3.38 to 10.56 and 3.89 to 11.0 g kg-1 in surface and subsurface horizons, respectively. The newlinedifferent forms of K were positively correlated with each other in soils of paddy-paddy newlinesequence indicating its dynamic equilibrium compared to soils of sunflower-bengalgram newlinesequence where no dynamic equilibrium exists between different forms of K. The soils of newlinepaddy-paddy sequence had higher K fixation compared to soils of sunflower-bengalgram newlinesequence. The mineralogy of soils revealed the dominance of smectite in the clay fraction in newlineboth cropping sequence. The paddy, sunflower and bengalgram crops have responded to newlinepotassium application in both kharif and rabi seasons in a cropping sequence involving newlinepaddy-paddy and sunflower-bengalgram. The potassium balance sheet was negative in soils newlineof both the cropping sequences. newline