Effects Of Combined Application Of Manure With Nitrogen Fertilizer On The Nitrogen Fractions And The Diversity Of Denitrifying Microorganisms In Greenhouse Tomato Soils

Denitrification is an important part of nitrogen cycle,and the waste of soil nitrogen fertilizer is intensified through denitrification,and the greenhouse effect is enhanced.Traditional research has mostly focused on the effects of changes in soil physical and chemical properties on denitrification intensity,functional gene abundance,and related microbial community structure under different environmental conditions.The effect of the change of nitrogen fractions caused by fertilization on denitrification was ignored.Therefore,this experiment is based on the Shenyang Agricultural University Long-term Positioning Fertilization Test as a platform,choose long-term non-fertilization?N₀?,single application of double nitrogen fertilizer?N₁?,double nitrogen fertilizer?N₂?,single application of organic fertilizer?MN₀?,organic fertilizer combined with single nitrogen fertilizer?MN₁?and organic fertilizer combined with double nitrogen fertilizer?MN₂?.By measuring the changes of soil nitrogen fractions and denitrifying microbial community structure after applying organic fertilizer and nitrogen fertilizer,the effects of long-term organic fertilizer and nitrogen fertilizer on soil nitrogen fractions and denitrifying microorganisms diversity were explored,with a view to scientifically fertilizing and improving Provide theoretical basis for nitrogen fertilizer utilization rate and greenhouse gas emission reduction.The main research results of this experiment are as follows:1.The content of soil total nitrogen?TN?in the treatment without organic fertilizer application?N₀,N₁,N₂?increased with the increase of nitrogen application,and the acidification of the soil also increased with the increase of nitrogen application,compared with N₀,the p H of N₂ is reduced by 2.11 units.The soil water content?SWC?decreased with the increase of nitrogen application,and the changing trends of available potassium?AK?,available phosphorus?AP?,and electrical conductivity?EC?decreased first and then increased.After combined application of organic fertilizers?MN₀,MN₁,MN₂?,soil TN increased significantly.And organic matter?OM?,AK,AP,and SWC all showing a trend of increasing first and then decreasing,and and the soil acidification phenomenon was alleviated.2.Nitrogen application alone did not increase the content of mineral nitrogen?Nmin?,but Nmin significantly increased after the application of organic fertilizer;the content of soil nitrate nitrogen?NO₃^--N?increased with the increase of nitrogen application,and the variation range was 12.82⁷3.92 mg/kg;the change trend of ammonium nitrogen?NH₄⁺-N?is opposite,the range of change is 83.80²14.97 mg/kg.After applying organic fertilizer,Nmin and NO₃^--N both increased with the increase of nitrogen application,while NH₄⁺-N decreased first and then increased.By comparison,NO₃^--N is the main contributing factor of potentially mineralizable nitrogen?PMN?.The proportion of potential mineralized nitrogen?PMN/TN?in the soil with single nitrogen fertilizer application is larger than that with organic fertilizer application,and the soil mineralization ability is stronger.The mineralization ability of the soil without fertilization for a long time is the weakest.3.The organic nitrogen content of the soil increased significantly after applying organic fertilizer.Comparing the proportion of acid-hydrolysis nitrogen to total nitrogen,it can be found that the proportion of unknown nitrogen?UN?in acid-hydrolysis nitrogen increases significantly after fertilization,and most fertilizers applied to the soil are stored in a stable UN form.Nitrogen fertilizer has no significant effect on the proportion of particulate organic nitrogen?PON?,the content and proportion of microbial biomass nitrogen?MBN?and soluble organic nitrogen?SON?are significantly reduced,but the content and proportion of light component organic nitrogen?LFON?significantly increased.The proportion of SON decreased significantly after fertilization,only 1.15%¹.33%,and the leaching loss of SON after applying organic fertilizer was effectively alleviated.4.Through high-throughput sequencing analysis,nir K denitrifying microorganisms are distributed in Archaea,Bacteria and Unclassified flora,and the proportion of ?-proteobacteria in proteobacteria is the largest.The dominant genus of N₂ treatment was Nitrosospira,and the dominant genus of MN₂ treatment was unclassified_fBradyrhizobiaceae.nir S is only in the Bacteria and unclassified_Unclassified,the proteobacteria in the Bacteria are only unclassified_Proteobacteria.The relative abundance of unclassified_Proteobacteria increases with the increase of nitrogen application.Nos Z is distributed in Bacteria and unclassified_Unclassified.Proteobacteria are also the main species in bacteria.unclassified_Proteobacteria account for the largest proportion in different fertilization treatments,but the relative abundance of each genus of bacteria varies significantly in different fertilization treatments.5.The diversity and richness of nos Z denitrifying microorganisms are much higher than that of nir K and nir S.Nos Z and nir K have the highest diversity and richness in N₁,nir S has the highest richness and diversity in N₀,and nitrogen application will reduce the diversity and richness of nir S,while the diversity and richness of nir K and nos Z denitrifying microorganisms degree will be suppressed only in excessive nitrogen application.nir K denitrifying microorganisms are more sensitive to fertilizer types than nos Z denitrifying microorganisms,and the community structure of soil nir S denitrifying microorganisms is simpler than nir K and nos Z.6.The denitrification intensity of organic fertilizer treatment is the largest,in order: MN₁> MN₂> MN₀.The denitrification intensity without organic fertilizer treatment is weak,and there is no significant difference.It can be seen that the application of organic fertilizer can significantly increase the soil denitrification intensity,and the application of single nitrogen fertilizer has the highest denitrification intensity,and the application of excessive nitrogen fertilizer in soil denitrification intensity is suppressed.7.Correlation analysis shows that the correlation between soil organic nitrogen components and basic physical and chemical properties is higher than mineral nitrogen components.NO₃^--N and organic nitrogen components are significantly positively correlated with basic physical and chemical properties?except p H?.NH₄⁺-N and PMN showed a significant correlation with p H,and PMN showed a significant negative correlation with p H.8.The correlation between denitrifying microorganisms and p H is strong,while the structure of nos Z denitrifying microorganisms is more closely related to SWC and OM.The correlation between nir K denitrifying microorganisms and soil nitrogen fractions is relatively close,and the correlation between nos Z and active organic nitrogen fractionts is stronger.Overall,MBN has the strongest correlation with denitrifying microorganisms.The correlation between denitrification intensity and soil organic nitrogen fractions is stronger than mineral nitrogen,and there is also a certain correlation with denitrification microorganisms.