Deep banding of controlled-release potassium chloride increases soybean productivity by regulating microbial communities and improving potassium uptake

Abstract

While deep banding fertilization and controlled-release potassium chloride (CRK) application improve crop yields by optimizing potassium (K) spatial distribution and reducing its fixation by 2:1 clay minerals, there is still limited information on K fertilization strategies suitable for sustainable soybean production. In this study, a two-year field experiment was conducted to investigate how soybean growth, soil microbial communities, and K availability are affected by different fertilization methods (broadcast incorporation versus deep banding) and K fertilizer types (conventional potassium chloride (KCl) versus CRK). The results showed that deep banding led to 3.4 %–4.1 % and 3.3 %–4.5 % higher soybean yield and 3.0–5.7 and 2.7–6.9 percentage points higher K use efficiency (KUE) than broadcast incorporation in 2023 and 2024, respectively. Compared to conventional KCl, CRK significantly improved soybean yield and KUE by 7.4 %–8.1 % and 10.9–11.9 percentage points in 2023, and 9.7 %–11.0 % and 8.9–13.1 percentage points in 2024, respectively. Meanwhile, CRK promoted soil microbial diversity, soil K availability, and soybean physiological traits. Of all treatments, deep banding of CRK resulted in the highest microbial diversity and relative abundances of beneficial microorganisms such as Lysobacter and Sphingomonas, thereby promoting nutrient cycling, increasing soybean antioxidant enzyme activities and endogenous hormone contents, and ultimately improving soybean productivity. In conclusion, deep banding of CRK can significantly improve soybean yield and KUE. This study provides an important scientific basis for the management and optimization of K fertilization in soybean production in China.