| In order to explore the effects of tillage and straw return on soil bacteria and the mechanism of bacteria on soil organic carbon and water content,and find the most suitable combination of tillage and straw return,the effects of tillage and straw return on soil bacterial diversity and water use were studied in the long-term positioning experimental field of Agricultural Experiment Station of Shandong Agricultural University.In the experiment,two tillage methods were set up,namely,subsoiling and no-till,and straw was set at two levels,namely,straw returning to field(STs),straw not returning to field(ST0),no-till straw returning to field(NTs),and no-till straw not returning to field(NT0).The results are as follows:(1)Compared with no-till,subsoiling reduced soil bulk density,improved porosity,increased soil organic carbon and total nitrogen content,and decreased C/N and bacterial carbon in wheat season and increased C/N and bacterial carbon in maize season.Compared with nonreturning straw,the organic carbon content of surface soil increased by 18.58% and 19.15% in wheat and maize seasons,respectively.Straw returning increased surface total nitrogen content by 17.64% in wheat season and 23.80% in maize season.(2)The β-glucosidase activity in the subsoiling trench was lower than that between the two trenches.The β-glucosidase activity of NTs in maize season was higher than that of NT0,the fibrinose hydrolase activity of subsoiling straw returning ditch was higher than that between the two ditchs,and the fibrinose hydrolase activity of subsoiling straw returning ditch was higher than that between the two ditchs.Compared with no-till,subsoiling increased the catalase activity and urease activity in the deep layer of wheat season,regardless of straw returning to the field.Under the same tillage conditions,the straw returning treatment increased the catalase activity in 0-60 cm soil layer and the urease activity in surface soil,and the STs treatment increased the catalase activity and urease activity during the wheat season.(3)The dominant phyla of soil bacteria were Proteobacteria,Acidobacteria,Bacteroidetes,Verrucomicrobia and Actinobacte at the filling stage of wheat and maize ria,and the relative abundance of actinomycetes in wheat ranked the third.Compared with no-till,subsoiling increased the relative abundance of Acidobacteria,and the relative abundance of Blastomonas and Firmicutes in wheat season,and decreased the relative abundance of verrucobacteria,actinomyces in wheat season and Bacteroides in maize season.It increased the richness of soil bacteria and the richness and diversity of bacterial community in 0-20 cm soil layer of maize season.Under the same tillage conditions,compared with no-till,straw returning increased the relative abundance of Proteobacteria and Green Bayobacteria,and increased the diversity of soil bacteria in the filling stage of wheat season.Acidobacteria in the hot spot area of wheat was higher than that in the cold spot area,Proteobacteria in the hot spot area of maize was higher than that in the cold spot area.The relative abundances of Gp4 and Gp6 were higher between the two trenches of subsoiling straw returning than those of subsoiling straw returning,and the relative abundances of Gp3 and Gp1 were higher between the two trenches of subsoiling straw not returning than those of subsoiling straw not returning.(4)There was a significant correlation between soil bacteria and soil urease activity in wheat season.Soil bacteria promoted urease activity,increased nitrogen decomposition ability,reduced C/N,limited microbial reproduction,reduced enzyme activity,reduced organic carbon decomposition rate,and was conducive to organic carbon accumulation.There was a significant correlation between SOC and soil bacteria in the maize season,and soil bacteria increased enzyme activity,increased soil nutrient content,promoted microbial reproduction,and promoted the production of microbial biomass carbon.There is a significant correlation between SOC and water content,as SOC provides nutrients for bacteria,enhances enzyme activities and cementing substances,promotes aggregate formation,improves soil structure and affects soil moisture.(5)Subsoiling improved soil structure,conducive to root tying,increased the number of wheat ears,maize kernel number,increased wheat yield and maize yield,and increased the water use efficiency,in wheat season by 17.58%,and the WUE in maize season by 23.90%.Under the same tillage method,the 1000-grain weight of wheat and maize was increased by6.51% and 4.38%,respectively.The water content of deep soil and water use efficiency of maize season were improved.NTs increased water content and water storage,and the water use efficiency of STs was significantly higher than that of other treatments.In conclusion,compared with other treatments,subsoiling straw returning(STs)increased soil organic carbon content,increased maize residue carbon and surface soil catalase,increased ear number and kernel number in wheat season,increased 1000-grain weight in wheat season and maize season,and improved crop yield and water use efficiency.Therefore,subsoiling straw returning(STs)is the best combination under the experimental conditions. |
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