How does rice-animal co-culture system affect rice yield and greenhouse gas? A meta-analysis.

Purpose: The introduction of aquatic animals into paddy fields is an effective strategy to improve rice yields and mitigate greenhouse gas emissions. However, it remains unclear how rice-animal co-culture systems affect methane (CH4) and nitrous oxide (N2O) emissions and rice yields, and the comprehensive drivers of management practices and pedo-climatic conditions have not been evaluated. Methods: A meta-analysis of 247 pairwise comparisons was employed to compare the CH4 and N2O emissions and rice yield between rice-animal co-culture (i.e., rice-duck, rice-fish, rice-crayfish, rice-crab, and rice-frog systems) and rice monoculture. Results: The results demonstrated that rice-animal co-culture significantly alleviated CH4 emission by 86.8%, improved rice yield by 49.2%, and had no significant effects on N2O emission relative to rice monoculture. Rice-animal co-culture was found to reduce the global warming potential by 12.9% and the greenhouse gas intensity by 4.9%. Considering rice yield improvement and greenhouse gas mitigation, the rice-duck, rice-fish, and rice-frog modes had great advantages over the rice-crayfish and rice-crab modes. Additionally, the effects of rice-animal co-culture on CH4 and N2O emissions and the rice yield were found to differ with the co-culture mode, aquatic animal density, feeding, nitrogen fertilizer rate, number of nitrogen applications, soil texture, soil pH, air temperature, and precipitation. Conclusion: Rice-animal co-culture systems have the great potential to increase agricultural productivity and alleviate environmental risks, which deserves to be acceptable and sustainable. [ABSTRACT FROM AUTHOR]