Effects Of Organic Materials Amendment On Soil Organic Carbon And Bacteria Community Varied With Aggregate Fractions In Sandy Soil

It is a hot issue to improve soil fertility and farmland productivity according to organic matter incorporation in circular agriculture and science and technology project for grain production.However,the incorporation way and mechanism of improving soil fertility needs further study.In this research,a positioned filed experiment with three organic matter incorporation such as pig manure,biogas residues and biochar was designed with a same nitrogen application amount,straw incorporation was selected as control.Changes of soil organic carbon pool,soil aggregate and bacterial community were analyzed to clarify the effects and mechanism of different organic materials amendment on soil improvement of low-yield sandy soil,and provide theoretical and practical basis for low and middle-yield soil fertilizing.The experiment began in October 2012 at China Agricultural University Wuqiao Experimental Station.The main conclusions in 2014-2016 are as follows:(1)The four organic material amendments incorporated to the field could promote the accumulation of soil organic carbon,in which the effects of biochar was the best Compared with the initial value,the accumulation of soil organic carbon increased by 126.03%,134.59%,114.04%and 467.12%under straw,biogas residues,pig manure and biochar incorporation in maize season of 2016;the SOC content of biochar was significantly higher than that of straw in 2014 to 2016(P?0.05);POC content in 0-20 cm soil of biochar was significantly higher than straw(P?0.05)during 2014 to 2016.MBC content of soil under biochar decreased by 2.9%-35.5%compared with straw in 2014-2016.There was no significant differences between pig manure and straw(P?0.05).The SOC content of biogas residue was 3.0%-19.8%and 4.7%-41.8%higher than that of the straw at 0-10 cm and 10-20 cm,respectively.(2)Compared with straw,biogas residue,pig manure and biochar increased 2-8 mm aggregate associated C than that of straw,but MWD in straw was higher than that of biogas residue,pig manure and biochar.In 2016,compared with the straw incorporation,the biogas residue mainly improved the 2-8 and 0.25-2 mm,pig manure improved 2-8 mm and biochar improved 2-8 mm,0.25-2,0.053-0.25 and<0.053 mm particle size bound carbon respectively.Compared with the initial value,the MWD in 0-10 cm soil increased by 305.26%,194.74%,205.26%and 142.11%under straw,biogas residues,pig manure and biochar incorporation while in 10-20 cm it increased by 158.82%,76.47%,105.88%and 47.06%respectively in maize season of 2016.In general,the trends of MWD in different treatments were straw>biogas residue,pig manure>biochar.(3)Different organic amendments altered the structure of soil bacterial community.The reason was associated with the impact of organic amendments on the difference in soil SOC content and pH under various amendments.The effect of different organic materials on bacterial a-diversity was not significant.The abundance of Proteobacteria under the biochar amendment was significantly lower than that under the straw amendment(P?0.05).The abundance of Acidobacteria under biochar,biogas residue,and pig manure amendments were reduced remarkably by 65.0%,34.9%and 40.7%as compared with straw amendment,respectively.Regression analysis showed that soil SOC content was significantly corrected with PCoAl and PCoA2,in the meanwhile,soil pH was significantly corrected with PCoA1.(4)Different organic amendments altered the diversity and structure of bacterial community under various soil aggregates,and the major reasons for change were the change of soil TOC and SOC content due to the various organic amendments.Biogas residue and pig manure and compared to straw,residue and pig manure improved bacterial a-diversity in 0.053-0.25 mm of 0-10 cm layer.Biochar treatment increased Chao index and decreased Shannon index in 0.053-0.25 mm and<0.053 mm aggregates.Biogas residue increased the abundance of Nitrospirae and decreased the abundance of Actinobacteria in four aggregates when compared to straw.In this study,the effect of four kinds of organic materials amendment on soil DOC,SOC,pH and AK were the main factors which caused the change of soil microbial community.Overall,there was no significant difference between biogas residue and straw on soil organic carbon,but increased the bacterial a-diversity in 0.053-0.25 mm fraction,and enhanced the abundance of Nitrospirae in four aggregates.Although biochar amendment promoted the accumulation of soil organic carbon,but the carbon in biochar was mainly inert carbon,which had negative effect on the improvement of physical and biochemical indexesr.Therefore,the effect of biogas residue amendment is best from the soil carbon sequestration and soil ecological health views in the North China Plain alkaline sandy soil.