MISHRA, V.N.DNYANESH RAMKRUSHNA, BHANDARKARPATIL, S.K.DAS, G.K.LAKHERA, M.L.2018-02-222018-02-222004http://krishikosh.egranth.ac.in/handle/1/5810041222Crop responses to potassium application in Vertisol were studied in ricewheat cropping system, at Instructional Farm in the Department of soil Science, IGAU, Raipur (C.G.). The objectives of the experiment were (i) to study the crop responses to fertilizer K application in rice-wheat cropping system (ii) to estimate the content and uptake of potassium by rice and wheat. (iii) to evaluate the different K fractions in Vertisol as influenced by rice-wheat cropping system. (iv) to monitor the potassium balance after two successive cropping season. (v) to study the fixation of potassium in Vertisol as influenced by K fertilization at surface and subsurface soil layer. The treatments consisted of five graded levels of fertilizer K application (0, 50, 100, 150 and 200 kg K2O ha-1) in four replication using RBD. The amount of all fractions was higher in surface layer (0-15 cm) than that in sub surface layer (15-30 cm). The order of dominance of different forms of potassium in the soil were non-exchangeable K >exchangeable K>available>water soluble K. The over all changes in different forms of K due to cropping indicates a decreasing trends in available and exchangeable K fractions but water soluble and non-exchangeable K did not show such trends. The initial value for total K (water-soluble + exchangeable + non-exchangeable K) was 1944 kg/ha that increased after rice season up to 2026 kg/ha then decreased to 1927 kg/ha after wheat crop season. No crop responses were observed to K fertilization in terms of yield and K uptake of rice and wheat crops. This indicates that soil under study is sufficient to meet the K requirement of the crops. The potassium balance indicates that application of 100-150 kg K2O/ha can sustain the K fertility status of the soil. Potassium fixation study reveals that the rate of fixation is enhanced in the treatment, which did not received any fertilizer K as compared to that receiving fertilizer K (@ 200 kg K2O ha-1). While comparing K fixation in twosoil depth, indicate that subsurface soil layer had slightly higher fixation as compared to that in surface layer.enThesis