Transformation Of Wheat Straw Carbon In Low Fertility Soil And Its Effect On Soil Microbial Community Structure

Recently,due to irrational use of arable land by humans,soil organic carbon content has decreased,adversely affecting high yields and stable yields.To increase soil organic carbon content and avoid environmental pollution caused by straw incineration,the state has advocated straw return to the fields.At present,many scholars have carried out a series of studies on the return of straw to the soil.However,in the low fertility soil,the research on the transformation and distribution of straw-derived carbon in soils and its effect on soil microbial communities are limited.Therefore,this study selected low-yield soils with different fertilization levels,and the wheat straw as the research objects.In order to explore the relationship between straw carbon and soil carbon pools,the distribution of ¹³C-wheat straw in the different soil organic carbon pools was analyzed by using the stable isotope tracer techniques.In addition,the high-throughput sequencing and BIOLOG analysis technology were applied to determine the effect of straw-derived carbon conversion process on the soil microbial community structure and activity.Combined with the soil physicochemical properties,ecological statistical analysis methods were used to figure out the main controlling factors impacting the soil microbial community strucutre.The main conclusions obtained in the study are as follows:?1?After wheat straw was added to low fertility soils with different fertilization levels,the SOC content increased by 28.90%-33.30%,of which the contribution of straw carbon to SOC was 34.07%-45.20%,with the highest rate in the soil without fertilizer?38.49%-45.20%?.After 7 d addition of wheat straw,the?¹³C-SOC rapidly increased,which was the rapid transformation stage of straw-derived carbon.From 7 to 14 d,the?¹³C-SOC slowly increased to the maximum and entered the slow conversion stage of straw-derived carbon;after 14-30 d,?¹³C-SOC Slight decline,but?¹³C-POC continued to increase,indicating that the process of straw carbon conversion to POC was increased;30 days later,straw-derived carbon conversion basically entered the stagnation phase.?2?Within 7 d after wheat straw addition,straw-derived carbon quickly entered the soil organic carbon pool,which was more easily distributed into the soil MBC?13.69%to14.69%?,followed by POC?2.93%-4.06%?and DOC?1.24%1.99%?.With the decomposition of straw,the proportion of straw carbon transformed into soil active and moderate organic carbon pools decreased.At the end of the experiment?180 days?,the ratio of straw carbon conversion to each organic carbon pool was POC?4.68%to 7.72%?,MBC?4.00%to 5.37%?,and DOC?0.12%to 0.16%?;different fertilization levels.Under the straw,there was no significant difference in the content of soil organic carbon pools after straw addition,but there was a big difference in the conversion and distribution of straw carbon.but there was a great difference in the conversion and distribution of straw carbon.The soil?¹³C-SOC,?¹³C-MBC and?¹³C-POC values in the non-fertilization or low fertilization treatment groups were significantly higher than the high fertilization levels,indicating that the addition of straw has a relatively higher contribution to the increase of organic carbon pools in low fertilization soils.?3?After the straw was added,the soil pH decreased significantly,with the lowest p H in the soil with high fertilization.Straw addition also significantly increased the content of soil TN,AN,AP and AK.The contents of TN and AN in soil increased greater in the soil without fertilizer application.The contents of AP and AK in soils were less affected by the fertilization level with straw added.?4?The dominant bacteria in the test soil were detected as Firmicutes,Proteobacteria,Actinobacteria,Chloroflexi,Acidobacteria,and Bacteroidetes.?Bacillus?,Planctomycetes?phytophyte?,Gemmatimonadetes?Glassia spp.?,among which bacteria belonging to Proteobacteria,Acidobacteria,Bacteroidetes,and Chloroflexi might be correlated with the straw-derived carbon transformation process.The dominant fungi detected in the testing soil were Ascomycota?Ascomycota?,Zygomycota,Basidiomycota,Basidiomycota,Ascomycota and Zygomycota,which might be mainly involved in the straw-derived carbon conversion.Straw addition can significantly increase the carbon source metabolic activity of low-fertilizer soil microorganisms,mainly for carboxylic acids,amino acids and polymer,with the highest diversity obtained on day of 14 after straw addition.?5?Straw addition significantly changed the soil physicochemical properties,whichimpacted the soil microbial community structure greatly.Redundancy analysis results showed that soil organic matter,alkaline N,available K,and pH were significant factors influencing the soil bacterial community structure during straw-derived carbon conversion,and soil organic matter,alkaline N and available K were significant factors affecting thesoil fungal community structure.