Effects of Long-Term Organic Fertilization on Productivity, Stability, and Nitrogen Use Efficiency in Rotation...

This study investigated how different organic fertilization practices affect productivity, stability, and nitrogen use efficiency in the rotation systems of the Hetao Irrigation District. The research was based on a long-term field experiment (2015-2025), with a chemical fertilizer-only treatment as the control (CK). Four organic fertilization treatments were evaluated: farmyard manure application (CM), straw incorporation (CS), green manure cultivation and incorporation (CG), and a combined green manure plus straw treatment (CGS). Based on three consecutive years of observations (2023-2025), the impacts of these treatments on crop yield, yield composition and stability, plant nitrogen accumulation and allocation, and nitrogen use efficiency were systematically analyzed. Both CM and CS significantly increased maize equivalent yield (MEY) compared with the other treatments, by 33.68-66.04% and 16.05-24.21%, respectively. CM's productivity advantage was primarily driven by higher biomass accumulation, whereas CS's advantage was largely due to improvements in the harvest index. In terms of stability, CM exhibited the lowest coefficient of variation (CV), indicating the highest static stability, while CS showed a regression coefficient (b_i) close to 1, indicating stronger dynamic stability. CM also significantly enhanced total plant nitrogen accumulation, nitrogen recovery efficiency (NRE), and nitrogen use efficiency (NUE), while optimizing nitrogen allocation to grain. CS significantly improved nitrogen internal efficiency (NIE), promoting more efficient conversion of absorbed nitrogen into grain yield. CG and CGS did not show clear advantages across productivity, stability, or most nitrogen use efficiency-related indices. Overall, in the Hetao Irrigation District, farmyard manure application is an effective strategy for achieving both high and stable yields, whereas straw incorporation offers stronger environmental adaptability. Both practices represent practical and effective approaches for improving the sustainability of rotation systems.