Effects Of Straw Returning And Nitrogen Fertilizer Application On Ricegrowth,Soil Properties And Microbial Diversity In The Early Stage

China stands as one of the nations blessed with copious straw resources globally.The rational and efficient exploitation of these straw resources holds immense significance in fostering sustainable agricultural development.Notably,the process of straw return is intricately intertwined with the pivotal role played by soil microorganisms.Soil microorganisms maintain the stability of ecosystems by regulating the biogeochemical cycling of soil nutrients.To balance the early straw decomposition,nitrogen competition between microorganisms and rice growth,this experiment used straw return with no fertilizer application（CK）and straw return with transplanting before（BF）as controls.Five basal fertilizer treatments were set up,including 100%compound fertilizer（S0）,20%carbon ammonium+80%compound fertilizer（S1）,40%carbon ammonium+60%compound fertilizer（S2）,60%carbon ammonium+40%compound fertilizer（S3）,and 80%carbon ammonium+20%compound fertilizer（S4）,to further investigate the effects of carbon ammonium and compound fertilizer ratios in basal fertilizers on soil physicochemical properties,crop growth,and soil microorganisms,The results showed that:（1）nitrogen fertilizer application significantly increased the content of ammonium nitrogen（NH₄⁺-N）and nitrate nitrogen（NO₃^--N）in the soil.In addition,as the ratio of carbon ammonium in nitrogen fertilizer application increased,the soil organic matter（SOM）content and soil p H showed a trend of initial decrease followed by an increase.The lowest soil organic matter content and p H were observed when the carbon ammonium content was 40%（S2）,while the easily oxidizable organic carbon（EOC）and dissolved organic carbon（DOC）showed the opposite trend.The highest content of easily oxidizable organic carbon and dissolved organic carbon were observed in the S2treatment.With the increase in the ratio of carbon ammonium in nitrogen fertilizer application,the aboveground fresh weight（AFW）,underground fresh weight（UFW）,root surface area（RS）,root volume（RV）,plant carbon（TC）,and nitrogen accumulation（TN）of rice plants showed an initial increase followed by a decrease trend.Among them,the S2 treatment had the highest values,which were significantly different from the other treatments.（2）nitrogen fertilizer application significantly reduced theα-diversity of bacterial and fungal communities in the soil.With the increase in the ratio of carbon ammonium in nitrogen fertilizer application,theα-diversity of ammonia-oxidizing archaea（AOA）community showed an initial increase followed by a decrease,with the highest diversity observed in the S2 treatment.The trend was opposite for the ammonia-oxidizing bacteria（AOB）community,with the lowestα-diversity observed in the S3 treatment.The S2 treatment had the highest number of exclusive operational taxonomic units（OTUs）for bacteria,while the lowest number of exclusive OTUs for fungi was observed in the S2 treatment.The S2 treatment had the highest number of exclusive OTUs for AOA,while the S3 treatment had the lowest number of exclusive OTUs for AOB.（3）Chloroflexi,Actinobacteriota,Proteobacteria and Acidobacteriota were the main components of the soil environment.Ascomycota and Basidiomycota are the dominant fungi,Thaumarchaeota is the dominant AOA community in the soil,Proteobacteria is the dominant AOB community in the soil,treatment S2 significantly improves the actinomycetes The relative abundances of Chloroflexi,Proteobacteria and Acidobacteria were reduced;the Basidiomycota of treatment S2 was lower than that of other treatments.（4）The contents of ammonium nitrogen and nitrate nitrogen in soil were related to crop growth indicators（UFW,TC,TN,AFW,RV,RS）and Actinomycetes and Basidiomycota were significantly positively correlated,soil Available K,SOM,and Olsen P were significantly positively correlated with Proteobacteria and Ascomycota,and significantly negatively correlated with rice growth indicators;Soil p H was significantly positively correlated with Chloroflexi;Thaumarchaeota was associated with soil easily oxidizable organic carbon,dissolved organic carbon,crop total carbon content,crop total nitrogen content,root volume,fresh weight of aboveground parts,root area,underground There was a significant positive correlation between soil fresh weight and soil ammonium nitrogen content,and a significant negative correlation with soil p H,nitrate nitrogen,available phosphorus,organic matter and available potassium;（5）22 bacterial genera（including NB1-J,Xanthobacteraceae,SCI-84,etc.）were negatively correlated with soil ammonium nitrogen,nitrate nitrogen and plant total nitrogen,was positively correlated with soil organic matter,available phosphorus and available potassium.Moreover,a positive correlation was observed between 10bacterial genera（Geminicoccaceae,Nocardioidaceae,Caldilineaceae,etc.）and soil parameters encompassing ammonium nitrogen,nitrate nitrogen,and indicators associated with crop growth.Conversely,these bacterial genera displayed a negative correlation with soil constituents such as organic matter,available phosphorus,and available potassium.Fungal genera（Sordariaceae,Scytalidium,Sagenomella,Cercophora,etc.）were negatively correlated with soil ammonium nitrogen and plant growth-related indicators,and positively correlated with soil available potassium;The presence of Podospora exhibited significant positive correlations with soil parameters of ammonium nitrogen,nitrate nitrogen,and plant growth-related indices.However,in contrast,it displayed negative correlations with soil attributes including organic matter content,available phosphorus,and available potassium.Thaumarchaeota was positively correlated with plant total nitrogen and total carbon,and Crenarchaeota was positively correlated with plant root surface area and soil dissolved organic carbon,but negatively correlated with soil available phosphorus and organic matter.Archaea was negatively correlated with soil ammonium nitrogen,nitrate nitrogen,dissolved organic carbon,readily oxidizable organic carbon,and plant growth-related indicators,but positively correlated with soil organic matter,available phosphorus,and available potassium.Nitrosomonadales was positively correlated with soil p H,ammonium nitrogen,nitrate nitrogen,and dissolved organic carbon,but negatively correlated with soil organic matter,available phosphorus,and available potassium;Nitrosospira It was negatively correlated with aboveground fresh weight and root volume,and positively correlated with soil available potassium.In summary,the results showed that straw returning combined with nitrogen fertilizer significantly changed the soil physical and chemical properties and rice growth,and significantly promoted the decomposition and absorption of organic matter in the soil under S2 treatment.At the same time,straw returning to the field combined with nitrogen fertilizer significantly affected the community structure of soil microorganisms,increasing the relative abundance of Actinomycetes,Thaumarchaeota and Basidiomycota,and reached the highest in S2 treatment.Correlation analysis showed that soil The contents of ammonium nitrogen and nitrate nitrogen were significantly positively correlated with crop growth indicators and the communities of actinomycetes and basidiomycota.This shows that the reasonable combination of nitrogen fertilizer S2 under straw returning to the field can balance the nutrient requirements of soil microorganisms and rice,and optimize the structure of soil microorganisms.Therefore,it is of great significance to rationally apply nitrogen fertilizer under straw returning to the field for the rational use of straw resources and the promotion of sustainable agricultural development.