Chemical and biological factors influencing the reduction of methane emission by biofertilizers in lowland rice: a meta-analysis

Methane (CH4) emissions from flooded paddy soils represent a major pathway of greenhouse gas release from agricultural systems. This meta-analysis evaluated the effectiveness of biofertilizers in reducing methane emissions based on 32 peer-reviewed articles that met the inclusion criteria. Data were analyzed using a Hedges’d weighted random effects model, with biofertilizers type, soil chemical properties, and environmental conditions as moderator variables. The results showed that biofertilizers significantly reduced CH4 emissions (ES = −0.784; p < 0.001) and increased grain yield (ES = 2.233; p < 0.001), especially in low-nutrient soils, neutral pH, and tropical climates with temperatures ranging from 20 °C to 30 °C. However, biofertilizers did not show significant effects on N2O emissions, NH4+ and NO3− availability, and instead tended to increase CO2 emissions and global warming potential (GWP) values, particularly in fertile soils with high organic matter content. These findings confirm that the success of biofertilizers as CH4 mitigation agents is highly dependent on environmental conditions and microbial composition. Therefore, biofertilizers application should be context-specific and carefully targeted to maximize agronomic benefits while reducing potential environmental impacts.