长期秸秆还田对稻虾共作系统稻季甲烷排放的影响

Effect of long-term straw returning on methane emissions in rice season of rice-crayfish coculture

稻田甲烷排放是农业甲烷排放的主要来源。稻虾共作是稻田生态种养应用面积最大的一种模式,秸秆还田是稻虾共作模式一种重要农事操作。为研究长期稻虾共作和秸秆还田对稻虾共作系统稻季甲烷排放影响及其机理,本试验于2015年设稻虾共作秸秆还田(RC-S)、稻虾共作秸秆不还田(RC-NS)、水稻单作秸秆还田(RM-S)、水稻单作秸秆不还田(RM-NS)共4种处理,对7年后稻田稻季甲烷排放、土壤碳库指标及功能微生物(mcrA和pmoA)进行测定与分析。研究结果表明:稻虾共作模式显著降低甲烷排放,比水稻单作稻季甲烷累计排放降低1.42%~26.44%;而秸秆还田稻季甲烷排放显著增加15.18%~54.36%。4个处理甲烷累计排放量依次为RM-S>RC-S>RM-NS>RC-NS。通径分析结果显示:总有机碳(TOC)、微生物量碳(MBC)、可溶性有机碳(DOC)、产甲烷菌(mcrA)对甲烷排放的直接作用是促进的,而易氧化有机碳(ROC)、甲烷氧化菌(pmoA)对甲烷排放的直接作用是抑制的。研究结果表明,稻虾共作甲烷减排机理在于土壤ROC含量增加和产甲烷菌功能基因mcrA丰度的下降,秸秆还田甲烷排放增加主要是因为土壤ROC含量的降低以及土壤DOC含量和产甲烷菌mcrA基因丰度的增加。可见,稻虾共作缓解了秸秆还田所引起的甲烷增排效应。

Comprehensive planting and breeding in rice fields make full use of resources.A typical green rice cultivation method involving rice and aquatic animals is utilized since they are mutually beneficial.Methane emissions from paddy fields are the main source of agricultural methane emissions,and rice-crayfish co-culture is a model with the largest application area for the ecological cultivation of paddy fields.Straw return is important in rice crayfish models.Rice-crayfish co-cultures affect the physical and chemical properties of paddy soils by changing field engineering and straw organic matter input,thereby affecting methane emissions.To study the effect and mechanism of long-term straw returning on methane emission from rice-crayfish coculture in the rice season,four treatments were designed in 2015:rice-crayfish coculture and straw returning(RC-S),rice-crayfish coculture and straw removing(RC-NS),rice-monoculture and straw returning(RM-S),and rice-monoculture and straw removing(RM-NS).Methane emission,and the soil carbon pool index and functional microorganisms were monitored after 7 years.The results showed that,compared to the rice monoculture,the methane emissions of the rice-crayfish coculture were significantly reduced by 1.42%−26.44%;however,the meth-ane emissions of straw return significantly increased by 15.18%−54.36%.Path analysis showed that the direct effects of total organic carbon(TOC),microbial biomass carbon(MBC),dissolved organic carbon(DOC),and methanogenic bacteria(mcrA)on methane emissions were positively promoted,while the direct effects of easily-oxidizable organic carbon(ROC)and methanotrophic bacteria(pmoA)were negatively inhibited.Our research results show that the methane emission reduction mechanism of rice-crayfish coculture lies in increasing the ROC content in the soil and decreasing the abundance of the functional gene mcrA of methanogenic bacteria;however,straw return can increase methane emissions by reducing the ROC content and mcrA gene abundance and increasing the DOC content.Therefore,rice-crayfish coculture can alleviate the methane emission effect caused by straw returning to the field.This study provides data support for rice-crayfish coculture to reduce emissions and increase efficiency.