Potassium release behaviour and fixation potential of Vertisol under continuous sorghum-wheat cropping sequence

Potassium (K) mining is a major concern in declining K status of Vertisols in Central India due to significant nutrient demands and imbalanced fertilization under intensive cropping systems. Crop productivity and the sustainability of cropping systems can be directly impacted by declining K status. Potassium release and fixation is an important process influencing K availability to plants. The purpose of this study was to examine how 29 years of manuring and the application of inorganic fertilizers affected the potassium release and fixation potential in the Vertisol of Central India. Seven nutrient management treatments which included various combinations of fertilizer and farm yard manure (FYM) as well as absolute control were replicated in randomized block design three times. Surface soil samples were collected after 29 years of cropping in order to investigate the potassium fixing and release potential. Application of NPK+FYM resulted in a significant increase in soil organic carbon, available nitrogen, phosphorus, and potassium. In the last 29 years, the treatment of absolute control had the highest K fixation (80.8%), while NPK + FYM had the lowest K fixation (63.8%) with higher cumulative K release (502 mg kg -1 ). The lowest standard error values indicate that the reaction rates were reasonably well described by the first-order and parabolic diffusion equation. Wheat yield showed a strong correlation with the exchangeable K and the release rate constant of first-order equation and parabolic diffusion. Thus, it can be concluded that, the FYM with fertilizers could be used as a potential controlled release nutrient combinations in intensive sorghum-wheat cropping sequence to address precise fertilizer use, K mining and balancing in Vertisol.