Controlled-release phosphate fertilizer improves soil fertility and soybean productivity by regulating soil microbial diversity and composition and increasing enzyme activities

Phosphorus (P) is one of the most important macronutrients for soybean growth. The extensive application of conventional chemical P fertilizers has contributed to soybean yield increase but, at the same time, has also led to P buildup in soil and subsequent loss to the environment. Controlled-release P fertilizers (CRP) can improve crop P absorption and yield. However, it remains unclear how CRP application regulates soybean productivity by affecting soil microbial communities and soil enzyme activities. In this study, a two-year field experiment was conducted to investigate soybean productivity and assess the contributions of soil microorganisms and soil enzymes to soybean productivity, in the different P fertilization treatments, which included 100 % triple superphosphate (TSP), 80 % CRP-20 % TSP, and 60 % CRP-40 % TSP at three application rates each (90, 75, and 60 kg P ha-1). The results showed that compared with 100 % TSP, CRP application significantly improved soybean yield and P use efficiency (PUE) by 1.7 %-10.1 % and 1.1-12.8 percentage points in 2023, and 3.7 %- 12.9 % and 4.9-22.5 percentage points in 2024, respectively. Of all treatments, 80 % CRP-20 % TSP at 75 kg ha-1 (MHCP treatment) resulted in the highest soybean yield and PUE. Meanwhile, a higher proportion of CRP was more favorable for soil microbial diversity, P- and N-cycling enzyme activities, and a stable soil pH. MHCP treatment also obtained the highest microbial diversity and relative abundances of beneficial microorganisms, such as Bradyrhizobium, Lysobacter, Sphingomonas, and Flavisolibacter, thereby promoting soil enzyme activities, soil fertility, and soybean growth. In conclusion, CRP combined with TSP at an appropriate proportion and application rate can significantly improve soybean yield and PUE. This study provides an important scientific basis for the management and optimization of P fertilization in soybean production in China.