Long-term application of controlled-release potassium chloride increases maize yield by affecting soil bacterial ecology, enzymatic activity and nutrient supply

Context: Soil bacterial community critical for sustaining the ecosystem is sensitive to long-term cultivation, including fertilizer applications. Although have been a lot of controlled-release potassium chloride (CRK) studies, maybe those on soil bacterial ecology related to potassium use efficiency (KUE) and yield are very limited. Objectives: We investigated how different proportions of CRK affected soil bacterial diversity and community structure, carbon/nitrogen cycle enzyme levels, soil nutrient supply, and maize (Zea mays L.) yield.Methods: An eight-year (2014-2021) field experiment using different proportions (0%, 50% and 100%) of CRK at 113 kg K2O ha-1 was conducted to determine the optimal fertilization method.Results: Increasing the percentage of CRK boosted the diversity and abundance of the bacteria (Bacillus, Gaiella, and Sphingomonas) associated with the carbon and nitrogen cycle enzymes. It also enhanced the interaction intensity between taxa, as slow nutrient release led to taxa with comparable ecological niches coexisting and collaborating to decrease functional redundancy. Increased CRK improved soil fertility significantly, enhanced the composition and function of soil bacterial colonies, and explained 82.8% of the variation in the bacterial colonies; directly increased soil nitrogen cycling enzymes content and the bacterial community relative abundance, and indirectly increased soil nutrient supply by 7.1-38.6%, maize yield by 11.7-11.8% and KUE by 8.4-13.2% points.Conclusions: The higher percentage of CRK significantly enhanced the stability of soil bacterial ecology, improved soil available potassium, ammonium, nitrate, soluble nitrogen contents, and organic matter content, and increased maize yield and KUE. Implications: Long-term CRK application is a good regime to improve maize yield and KUE by regulating soil bacterial biodiversity, carbon/nitrogen cycle enzyme activities, and soil nutrient supply.