Contradictory instruments undermine the implementation of agricultural nutrient management policy mixes

Optimizing agricultural nitrogen (N) and phosphorus (P) nutrient application and crop structure regulation are common ways to control non‐point pollution. However, comprehensive effects of nutrient surplus and farmers’ revenue remain poorly understood. We applied fixed‐effect models using data from farm surveys to examine policy mixes in Eryuan County, China, on N and P pollution from cropland. The results showed that 73.8% of the surveyed farmers changed their crop choices, while the share of farmers using synthetic fertilizers reduced by 40.0% and those using organic fertilizers increased by 16.1% following the policy implementation. Consequently, N surplus was dramatically decreased by 72.5%, while P surplus remains largely unchanged. Analyzing the individual contributions of the two policy instruments revealed contradictory effects that led to inefficient P mitigation. Specifically, regulating crop choice was responsible for 89.7% and 402.3% of the reduction in N and P surplus, respectively, while controlling nutrient input (CNI) contributed only 10.3% to N surplus reduction but led to a 302.3% increase in P surplus. This indicates that excessive manure substitution (CNI) can result in pollution swapping between N and P. Moreover, farmers’ net revenues declined by 70.4% due to shifts in crop structure. In conclusion, this study addressed the contradictory effects within policy mixes and the potential trade‐offs between environmental gains and economic benefits, offering valuable insights for designing more effective nutrient management policies worldwide.