Substitution of chemical fertilizer by biogas slurry maintain wheat yields by regulating soil properties and microbiomes

At present, there is a lack of refined management for biogas slurry after toilet reconstruction, making it difficult to achieve safe treatment and resource utilization of biogas slurry. Utilizing biogas slurry instead of chemical fertilizers is able to significantly mitigate these issues. We established five fertilization treatments to investigate the impact of biogas slurry substitution on wheat growth, soil properties, and soil microbiomes in field experiments with varying proportions of biogas slurry. Utilizing small amounts of biogas slurry as a replacement for chemical fertilizers was able to maintain soil nutrient levels while sustaining wheat yield (from 2766.76 kg/hm² to 2973.13 kg/hm²), stabilize urease and catalase activities, and improve microbial communities. Additionally, using a minor amount of biogas slurry as a substitute for fertilizer resulted in an increase in the population of potentially beneficial bacteria and a decrease in the presence of potential fungal pathogens. Random forest analysis showed that the potentially beneficial bacteria (Stenotrophomonas, Streptomyces, Arenimonas), potentially fungal pathogens (Alternaria, Lectera, Fusarium), and consumer protists (Colpoda, Paracercomonas, Sandona) are the dominant predictors of wheat yields. Structural equation modelling showed that the replacement of chemical fertilizers by biogas slurry directly and indirectly sustained crop yield by altering soil characteristics and the microbial community. Our results showed that replacing 20 % of fertilizer with biogas slurry was concurrently able to maintain crop productivity while safeguarding the environment. These results improve our comprehension of the impact of various biogas slurry substitutes and hold significant theoretical importance for advancing the utilization of biogas slurry in the future.