Cropping system regulates the optimal organic substitution ratio via soil-plant nitrogen and phosphorus transformation and utilization.

INTRODUCTION: The optimal of organic fertilizer for substituting chemical fertilizer in a specific planting system is unclear. This study aimed to clarify how organic substitution regulates nitrogen (N) and phosphorus (P) transformation and utilization in the soil-wheat system under different cropping systems. METHODS: This study investigated three organic fertilizer substitution (0%, 25%, 50%) on N and P transformation and utilization in the soil-wheat environment under maize-wheat (MW), peanut-wheat (PW), and soybean-wheat (SW) cropping systems. Indicators related to rhizosphere soil N (N-acq) and P-acquiring (P-acq) enzyme activities, wheat root N and P metabolism enzyme activities, N and P nutrient accumulation and utilization, and yield. RESULTS: Organic substitution reduced the N-acq enzyme activity in the rhizosphere soil (2.50%-35.32%) and the mineral N (Nmin) content, but increased the P-acq enzyme activity (0.81% to 18.15%) and the available P (AP) content (0.68%-31.51%). It also enhanced the N (NR, GS, GDH, GOGAT) and P metabolism (ACP) enzymes in wheat roots, thereby promoting the accumulation of N and P. Under the MW, the 25% substitution rate performed best root N and P metabolism enzyme activities, N and P-use efficiency (NUE, PUE), and grain N and P accumulation. Meanwhile, under the SW and PW, the 50% substitution rate was superior. DISCUSSION: The key drivers of yield formation were N related parameters under the MW and P related parameters under the SW and PW. Present study, 25% organic substitution is suitable for the MW cropping system, while 50% suits SW and PW cropping systems.