Potential effect of biogas slurry application to mitigate of peak N2O emission without compromising crop yield in North China Plain cropping systems

Abstract

Biogas slurry (BS) produced from anaerobic digestion of livestock manure can be benefit for crop yields and soil fertility in cropping systems as compared to sole synthetic fertilization, but its impact on nitrous oxide (N₂O) emissions is inconsistent in the literatures. The North China Plain (NCP) serves as a vital agricultural region in China, contributing approximately 40 % of the nation's total wheat and maize production. However, owing to the lack of relevant field studies, the understanding of how BS affects crop yield and N₂O emissions in NCP remains unclear. Here, we assessed the effects of BS substitution (0 % substitution, CF; 50 % substitution, 50%BS; 100 % substitution, 100%BS) on the amount and sources of N₂O emissions by monitoring N₂O fluxes combined with the isotopomer ratios of soil-derived N₂O in the NCP. The results showed that, compared with the control, CF, 50 % BS, and 100 % BS significantly increased wheat grain yield by 66.1 %–67.9 % and silage maize yield by 46.3 %–53.3 %, respectively. Compared with CF, 50%BS reduced N₂O emissions by 40.1 % in the wheat season and by 35.5 % maize season, while 100%BS reduced N₂O emissions by 31.9 % in the wheat season and by 49.2 % in the maize season. Further site preference analysis revealed that nitrification and fungal denitrification together contributed to 40.3–44.9 % of the peak N₂O emissions in CF, 50%BS, and 100%BS, with no significant differences in SP values among them. Compared with CF, 100%BS significantly reduced the copy numbers of AOB-amoA, nirK, and nirS by 65 %, 41 %, and 35 %, respectively, which may be key factors in reducing N₂O emissions. Our results showed that the partial substitution of chemical fertilizers with BS is an efficacious practice for maintaining crop yields while simultaneously reducing N₂O emissions in the NCP.