Effects Of Successive Years Of Corn Straw Return On Soil Nutrients And Soil Bacterial And Fungal Community Structure

In order to speed up the resource utilization of straw,we adopt the method of continuous multi-year corn straw crushing and plowing to return the whole amount of straw to the field to improve the fertility of black soil,reduce the environmental risk and achieve the purpose of black land conservation.Straw decomposition is closely related to soil microorganisms,which are complex and diverse,and have important effects on the degradation of corn stover,organic matter decomposition and nutrient recycling in the soil.Traditional soil microbial research methods are not comprehensive enough to investigate the role of soil microbial communities on straw decay by combining amplitude sequencing technology and various soil microbial analysis methods.To address this issue,this paper investigates the effect of soil microbial community on stover decay in a tillage system with continuous years of full shredding and deep tillage of maize stover(5-9 years)and adjacent plots with continuous years of stover leaving the field,focusing on different scenarios(stover not returned to the field CK,returned to the field SR5 for 5 years,returned to the field SR7 for 7 years and returned to the field SR9 for 9 years)and key fertility periods of maize: pulling stage V12,tassel stage R1 and tassel stage R2.The soil microbiological mechanisms that improve soil physical and chemical properties and soil fertility under different scenarios(CK,SR5 for 5 years,SR7 for 7 years and SR9 for 9 years,as well as key fertility periods of maize: V12,R1 and R3 during the tassel stage),combined with modern molecular biology techniques,were used to elucidate the characteristics of soil microbial community structure in straw returned fields for many years,and to provide theoretical basis for the promotion of straw-returning technology.The main results are as following.1.Successive years of full crushing and deep turning of maize straw returned to the field improved soil fertility.Soil microbiology carbon showed the highest performance in SR7 treatment,which significantly increased by 52.21% compared with the unperturbed treatment;straw return significantly increased soil microbiologist carbon to nitrogen ratio,which increased by 85.10%,212.19% and 33.32% in SR5,SR7 and SR9 treatments,respectively,compared with the unperturbed treatment;straw return increased soil total nitrogen content,which increased by3.26% in SR5 treatment compared with the unperturbed treatment.Returning straw to the field significantly increased soil total phosphorus content,with SR5 and SR9 treatments increasing by7.15% and 4.24%,respectively,compared with the unperturbed field;returning straw to the field increased soil fast-acting phosphorus content,with SR5 treatment increasing by 23.31% compared with the unperturbed field;returning straw to the field significantly increased soil total potassium content,with SR5,SR7 and SR9 treatments increasing by 1.54%,2.15% and 6.37%,respectively,compared with the unperturbed field;returning straw to the field The soil organic matter content was increased by 16.03%,8.27% and 4.35% in the SR5,SR7 and SR9 treatments,respectively,compared with the unperturbed treatment.2.The maximum amount of corn stover crushed and tilled in successive years increased the difference of soil microbial beta diversity.Compared to unperturbed fields,returning the straw increased the number of bacterial-specific OTUs but decreased the number of fungal-specific OTUs in SR7 and SR9 treatments.Straw return increased the differences among soil microbial communities,with the greatest differences between the SR9 and unperturbed treatments.Straw return increased the response of soil bacteria to soil water content,MBN,MBC/MBN,and an,and straw return increased the response of soil fungi to soil water content,MBN,MBC/MBN,p H,SOM,TN,and an.3.Soil microbial structure was more complex in continuous years of extensive shredding and tillage of maize stover returned to the field.Compared to unperturbed fields,straw return increased the number of significantly different species,with more bacterial phyla than fungal phyla,making the soil bacterial network complex and increasing the value of topological attributes,including the number of nodes,connections,average degree and connected components.However,the complexity of the fungal network reduced,and SR5,SR7 and SR9 treated the network complexity gradually increased.4.Soil microorganisms functioned more powerfully when the corn stover was returned to the field with full shredding and tillage for consecutive years.Compared with unperturbed fields,field return enhanced aerobic ammonia oxidation,aerobic nitrite oxidation,nitrification and intracellular parasitic bacteria of the soil,increased the ritualistic function of SR5 treatment,enhanced phenomenology heterotrophic function of the return treatments in R1 and R3 periods,and increased urea decomposition function of each return treatment in R3 period.Soil fungi were dominated by saprophytic nutrient mode with a cumulative percentage of 76.72%.