Effects Of Straw Incorporation On Greenhouse Gas Emission From Soil Aggregates Of Different Size

Agricultural ecosystem is an important source of greenhouse gas emissions.Straw return is an important agricultural practice,which can avoid wasting of nutrients and environmental pollution caused by straw burning.At the same time,straw can provide abundant nutrients,stimulating soil microbial activities,modifying the mineralization of soil organic matter.Soil aggregates can protect organic matter physically.Different size aggregates may have different properties and they may protect organic matter differently.Therefore,the mineralization of organic matter in different size aggregates may be different after adding straw,which will further affect the soil C and N cycle,thus affecting the greenhouse gas production and emissions.The effects of straw incorporation on greenhouse gas emissions from different size aggregates are not clear yet.In order to explore the effect of straw incorporation on greenhouse gas emissions from different size aggregates in sandy loam soil,in this study we collected soil from Jingzhou and designed indoor incubation experiment of different size aggregates with straw incorporation.The main research were as follows:?1?Adding straw increased emission flux and cumulative emissions of CO₂ and N₂O significantly?except 0.25-1mm?,and had no significant effect on CH₄ emissions.?2?There was no significant difference in CO₂ emission flux in treatments without straw.After adding straw,the CO₂ average emission flux and cumulative emissions of<0.25 mm,1-2 mm,0.25-1 mm and bulk soil decreased successively.The CO₂ cumulative emission of <0.25 mm size aggregate had increased by 11 times after adding straw,while 0.25-1 mm size aggregate had increased by 7 times after adding straw.The N₂O average emission flux without straw of 0.25-1 mm,1-2 mm,bulk soil and<0.25 mm decreased successively,and N₂O cumulative emission without straw of 1-2mm,0.25-1 mm,bulk soil and <0.25 mm decreased successively.After adding straw,the N₂O average emission flux and cumulative emission of 1-2 mm,bulk soil,<0.25 mm and0.25-1 mm decreased successively.Among them,the N₂O emission flux and cumulative emission of 0.25-1 mm size aggregate had decreased significantly after adding straw,while the other three had increased after adding straw.CH₄ emission from different size aggregates had no significant difference.?3?The activities of oxidase and hydrolase,the contents of soil dissolved organic carbon and mineral nitrogen was different in different size aggregates,while they had different changes after adding straw.In all soil properties,cellobiohydrolase?CB?,leucine aminopeptidase?LAP?,?-N-acetylglucosaminidase?NAG?,phenol oxidase?pox?,DOCand NO₃^--N could influence emission of CH₄,CO₂ and N₂O most,which could account for 80.3% of greenhouse gas emissions.DOC and NO₃^--N could account for 32.3% of greenhouse gas emissions,and CB,LAP,NAG and pox could explain 53.8% of greenhouse gas emissions.Both LAP and DOC had positive contribution to three gases emission.