Reducing ammonia emissions and nitrate leaching in wheat-maize systems by substituting chemical fertilizers with...

Ammonia (NH₃) emissions and nitrate (NO₃ ^-) leaching from crop fields are major contributors to non-point source environmental pollution.

To optimize the resource utilization of pig manure and reduce gaseous and liquid nitrogen losses in wheat-maize rotation systems, five treatments were investigated, including 15% (OF₁₅), 30% (OF₃₀), and 45% (OF₄₅) substitution of chemical fertilizer nitrogen with pig manure as well as a no-nitrogen control (CK) and local farmer's fertilization method (CF). Ventilation-type NH₃ capturing devices and NO₃ ^- leaching lysimeters were used to systematically investigate the nitrogen (N) dynamics in the wheat-maize rotation systems from 2022 to 2024.

The pig manure substitution ratio had profound impacts on NH₃ emissions, NO₃ ^- leaching, and crop yields. When the substitution ratio of pig manure was 30%, wheat produced the highest average yield at 9,181 kg ha^-1, with 0.256 g kg^-1 lower NH₃ emissions per unit of grain output compared to chemical fertilization alone. Similarly, the maize yield was 10,897 kg ha^-1, with 0.17 lower NH₃ emissions per unit of grain.

Comprehensive analysis suggests that 30% pig manure substitution ratio in OF₃₀ will be optimal to achieve environmental and yield benefits simultaneously.