Effects Of Different Irrigation And Fertilization Managements On Nitrogen Cycle Functional Microbes In Greenhouse Vegetable Soils

Greenhouse vegetable soil is an important source of N₂O emissions,mainly caused by microbial nitrification and denitrification processes.Different irrigation and fertilizer management systems lead to changes in the physicochemical property of the greenhouse vegetable soil,which affect the nitrifying and denitrifying microorganism in the soil.In order to study the changes of nitrifying and denitrifying bacteria structure and the impact on N₂O emissions in different irrigation and fertilizer management systems,find a scientific irrigation and fertilization managements for greenhouse vegetable production.Four kinds of irrigation and fertilizer management systems were set up in the Experimental Base of the Chinese Academy of Agricultural Sciences,namely;Control treatment?CK?,habit treatment of farmers?FP?,drip irrigation and fertilizer treatment?FPD?,optimized drip irrigation and fertilizer treatment?OFPD?.The physicochemical properties of organic carbon,ammonium nitrogen and nitrate nitrogen in soil were measured.Ammonia-oxidizing bacteria?AOB?and ammonia-oxidizing archaea?AOA?,nirS and nirK denitrifying bacteria community compositions in soil were studied,using high-throughput sequencing.The number of AOB and AOA were determined used quantitative PCR.The relationship between microbial community structure and environmental factors were also analyzed based on statistical methods.The study obtained the following results;?1?The OFPD soil had highest concentration of nutrients?organic carbon,phosphorus,potassium,ammonia nitrogen,nitrate nitrogen?,and N₂O emission was4.94±1.69 kg·N/ha,it higher than CK and FP,but lower than FPD.Part of the organic fertilizer instead of chemical fertilizer reduced the N₂O emission.Drip irrigation reduces nitrogen leaching and conserves a large amount of soil nitrogen.Under the same amount of nitrogen fertilizer input,N₂O emissions increase.?2?The nitrification potential trend was OFPD>FPD>FP>CK.As nitrification potential increased,N₂O emissions increased.Part of the organic fertilizer instead of chemical fertilizer and drip irrigation significantly increased the nitrification potential in the soil,while N₂O emissions were lower than FPD,which may be related to organic fertilizer application and increased soil nitrate nitrogen residue.?3?Soil pH and phosphorus content had significant effects on the community structure of AOB?P<0.05?.Nitrosospira was the dominant genus?33.3%-50.7%?,in OFPD was highest.Phosphorus and organic carbon had significant effects on the community structure of AOA?P<0.05?.Nitrosopumilus was the dominant genus?17.7%-39.6%?,in CK was the highest.Therefore,fertilizer and drip irrigation significantly increased the abundance of Nitrosospira in AOB,while the abundance of Nitrosopumilus was reduced and Nitrososphaera was increased in AOA.The N2O emissions had a significant effected on the structure changes of AOB and AOA?P<0.05?.?4?Number of AOA in the four managements was higher than AOB.Analysis found that fertilizer significantly increased the number of AOB whereas drip irrigation increased AOA.As the number of AOB increased,N2O emissions increased.?5?Rhodanobacter was the dominant genus in CK,FP,and FPD,while in OFPD,it was Pseudomonas.Fertilizer and drip irrigation significantly changed the community structure of nirS denitrifying bacteria in the soil.Rhizobium was the dominant genus?2.6%-10.6%?and fertilizer drip irrigation increased Rhizobium abundance.N2O emission was positively correlated with the diversity of nirK denitrifying bacteria?R=0.6034 P=0.0452?,but not with the diversity of nirS denitrifying bacteria.In summary,different irrigation and fertilizer management patterns lead to changes in community structure of AOB,AOA,nirS and nirK denitrifying bacteria and changes in the amount of AOB and AOA,which have a significant impact on N₂O emissions.The application of some organic fertilizers instead of chemical fertilizers has relatively low N₂O emission and high soil nutrient content,which is a relatively scientific management model.