How biogas slurry irrigation replacing chemical fertilizers affects farmland greenhouse gas emissions—in-depth exploration with a meta-analysis

Applying biogas slurry to replace chemical fertilizer is crucial for agricultural sustainable development, yet comprehensive and systematic analyses of its impact on greenhouse gas emissions are scarce. A meta-analysis through 152 groups of data from 32 literatures was conducted in this study to evaluate the impact of replacing chemical fertilizer with biogas slurry on greenhouse gas emissions and global warming potential. Overall, this practice led to an increase in the global warming potential. Specifically, in soils with poor properties, biogas slurry can not only improve soil but also reduce greenhouse gas emissions. When the N application rate ≥ 230 kg hm -2 , greenhouse gas emissions are reduced. Additionally, grasses had the greatest effect on the exacerbation of global warming, while cereals had the least effect under the application of biogas slurry instead of chemical fertilizer. Biogas slurry from pig manure has the weakest impact on increasing the global warming potential. Especially when the chemical fertilizer type is urea, the replacement effect is better. Replacing 70%-100% of chemical fertilizer with biogas slurry can reduce greenhouse gas emissions, while complete replacement instead exacerbates. When the fertilization frequency of biogas slurry ≥ 3 times, the global warming potential can also be reduced. To effectively minimize greenhouse gas emissions, the soils where biogas slurry replaces chemical fertilizer should be selected from low-fertility acidic soils (e.g., pH ≤3.33 and organic matter content ≤17.5 g kg -1 ) based on the results of this study alone, and better effects can be achieved when the N application rate is greater than 270 kg hm -2 .