Effects Of Corn Straw Deep Incorporation With Different Years On Organic Carbon And Microbial Community Structure In Black Soil

In recent years,the disposal of crop straw waste and the degradation of black soil are two major problems facing our country.Returning straw to the field has become one of the important agricultural measures for the improvement of black soil.Soil organic carbon(SOC)plays an extremely important role in soil fertility,structure and carbon sink as a global carbon cycle.Soil microorganisms also play an irreplaceable role in maintaining soil health and quality.Bury the cron straw at a depth of(20-40 cm)in the subsurface layer of the soil,break the bottom of the plow,extending from the previous surface fertilization to sub-surface fertilization.It is not only conducive to the accumulation of organic matter in the subsurface layer that has been in a"starved"state for a long time,but also combines the use of straw as a resource with soil fertility,which can achieve soil carbon sequestration and CO₂ emission reduction.Therefore,studying the influence mechanism of corn straw deep incorporation with different years on SOC and microbial community structure in black soil is of great significance for revealing the biological mechanism of soil carbon sequestration and fertilization by returning straw to the field.In this study,the field location experiment method was used to study the effects of corn straw deep incorporation with different years(1 year,3 years,5 years)on the SOC and microbial community structure in a black soil.The main research results are as follows:(1)With the increase of corn straw deep incorporation years,the SOC content of the surface layer(0-20 cm)and subsurface layer of the soil first decreased and then increased.Compared with the control(CK)treatment without the corn straw deep incorporation,the SOC content of the soil surface and subsurface layer was significantly reduced when the corn straw deep incorporation for 1 year.With the increase of corn straw deep incorporation years,the SOC content significantly increased,when the corn straw deep incorporation for 5 years.The SOC content of the soil surface and sub-surface layer significantly increased by 18.88%and 24.92%respectively to the corn straw deep incorporation for 5 years compared with the corn straw deep incorporation for 1 year,and 8.94%and 7.87%compared with CK.(2)Corn straw deep incorporation with different years also significantly affect the aggregate composition of the soil surface and subsurface layers.Corn straw deep incorporation for 1,3 and 5 years significantly increases the content of 2?0.25 mm large aggregates in the surface and subsurface layers of the soil by 20.65%?31.32%,12.94%?20.19%and8.28%?16.76%,respectively.The effect of corn straw deep incorporation for 1 year is the most significant.With the increase of corn straw deep incorporation years,the increase of large aggregates of 2?0.25 mm gradually decreased,but the content of large aggregates of 2?0.25 mm in the surface and subsurface layers was still significantly higher than that of CK when the corn straw deep incorporation for 5 years.(3)The SOC content of the aggregates of each particle size was significantly reduced after the corn straw deep incorporation for 1 year,but with the increase of corn straw deep incorporation years,the SOC content of the aggregates of each particle size increased significantly.When the corn straw deep incorporation for 5 years,the SOC content of aggregates in the subsurface layer of the soil was significantly higher than that of CK by7.02%?8.33%,the SOC content of 0.25?0.053 mm microaggregates and<0.053 mm powder+clay particles in the soil surface layer was significantly higher than that of CK,and there was no significant difference of>2 and 2?0.25 mm large aggregates with CK treatments.The corn straw deep incorporation for 5 years is more conducive to the accumulation of SOC.(4)Corn straw deep incorporation with different years significantly affect the humus composition of surface and subsurface soils.With the increase of corn straw deep incorporation years,the water-soluble organic carbon(WSOC)content of the soil surface and subsurface layer increased first and then decreased.Corn straw deep incorporation for 1 year significantly increased the WSOC content of the soil surface and subsurface layer.Comparing different soil layers,the WSOC content of the subsurface soil layer is higher than that of the surface layer.With the increase of corn straw deep incorporation years,the carbon content of humic substances in the surface and subsurface layers of humic acid(HA),fulvic acid(FA)and humin(HM)all decreased first and then increased.Compared with CK,corn straw deep incorporation for 1 year significantly reduces the carbon content of HA,FA and HM in the surface and subsurface layers of the soil.After that,with the increase of corn straw deep incorporation years,the carbon content of each component of the humus in the surface and subsurface layers of the soil continues to increase.When the corn straw deep incorporation for 5 years,the HA,FA and HM contents in the surface layer of the soil are significantly higher than that of CK treatment by13.51%,17.72%and 9.73%,respectively,and the contents of HA,FA and HM in the subsurface layer are higher than that of CK treatment by 18.31%,10.91%and 7.07%,respectively.With the increase of corn straw deep incorporation years,the hue coefficients(?lg K)of HA and FA of the surface and subsurface layers gradually decrease when the corn straw deep incorporation for 1 year.When the corn straw deep incorporation for 5 years,the?lg K values of HA and FA in the surface and subsurface layers of the soil are still significantly higher than that of CK,it shows that the corn straw deep incorporation with different years also simplifies the molecular structure of HA and FA in the surface and subsurface layers of the soil.Comparing different soil layers,the degree of humification of HA and FA in the subsurface layer of black soil is higher than that of the surface layer.(5)Corn straw deep incorporation with different years have a significant impact on the fungal community structure.With the increase of corn straw deep incorporation years,the diversity and richness of soil fungi showed a trend of first decreasing and then increasing.The corn straw deep incorporation for 3 and 5 years significantly increased the diversity and richness of the fungal community.The effect on soil fungal community structure varies greatly due to the different years of corn straw deep incorporation.The abundance of Basidiomycota as an important executor of straw degradation increased significantly after the corn straw deep incorporation for 1 year.The abundance of Ascomycota and Zygomycota of corn straw deep incorporation for 3 and 5 years has increased significantly because of their strong ability to decompose cellulose and refractory organic matter.At the genus level,the relative abundance of straw-degrading fungi such as Mortierella,unclassified?f??Chaetomiaceae,and Fusarium has been increased,among which Mortierella and unclassified?f??Chaetomiaceae are biological control fungi.Soil environmental factors have a significant impact on the structure of soil fungal community.(6)Corn straw deep incorporation with different years have a significant impact on the structure of bacterial community.Corn straw deep incorporation with different years increased the diversity and richness of bacteria,and with the increase of corn straw deep incorporation years,it showed a trend of first increasing and then decreasing.Corn straw deep incorporation with different years increases the relative abundance of Chloroflexi and reduces the relative abundance of Firmicutes.Acidobacteria,which has a positive effect on increasing SOC,significantly increase.The relative abundance of Sphingomonas has decreased.On the whole,the impact on soil bacterial community structure varies greatly due to different years of corn straw deep incorporation.Soil environmental factors have a significant impact on the structure of soil bacterial community.In summary,Corn straw deep incorporation with different years promoted the formation of large aggregates of 2?0.25 mm in the soil.Corn straw deep incorporation for 3 years and 5 years increased the SOC content of the soil and its aggregates at all levels,and improved the physical properties of soil aggregates on SOC.It is conducive to the accumulation and stability of SOC.The corn straw deep incorporation for 3 and 5 years has significantly increased the carbon content of HA,FA and HM in the various components of the soil surface and subsurface humic substances,simplifying the molecular structure of HA and FA,and renewing soil humic substances,which is conducive to improve soil quality and fertility.Corn straw deep incorporation for 3 and 5 years increased the richness and diversity of soil fungi,and the corn straw deep incorporation with different years could increase the richness and diversity of soil bacteria.Corn straw deep incorporation stimulates the increase in the abundance of straw-degrading bacteria,most of which are beneficial bacteria,which have a positive effect on the improvement of soil organic carbon.On the whole,the microbial community structure was optimized under the condition of corn straw deep incorporation.Corn straw deep incorporation has a positive effect on promoting soil organic matter and nutrient cycling,realizing carbon sequestration and improving soil fertility.