Effect Mechanisms Of Manure Application On Soil Fertility And Bacterial Community In Shajiang Black Soil

China is the country with the largest population,grain production,and food consumption in the world.Ensuring food security is crucial for stable development of China,and soil fertility is an important factor affecting crop yield and quality.At present,there are still amount of medium and low yield fields in China,which severely limits the potential of grain production.Improving soil fertility of medium and low yield fields is an important way to promote the production capacity of per unit area of arable land and ensure food security.Generally,agronomic management measures,such as organic fertilization input,facilitate the absorption and utilization of nutrients by crops,and improved soil fertility by provide sufficient energy and nutrients such as carbon(C),nitrogen(N),and phosphorus(P)directly.As important components of soil,microorganisms play essential roles in soil processes such as exogenous organic material degradation,material circulation and energy flow.However,there is currently limited understanding of the mechanism of organic fertilizer application on soil fertility and productivity in medium and low yield fields,and the mechanism of specific microorganisms in improving soil fertility still needs to be revealed.The Shajiang black soil was collected from Zhongke Taihe Experimental Station,which was one of the three typical medium and low yield fields in the Huanghuaihai Plain.And we conducted the following research through in-site field experiments and high-throughput amplicon sequencing of 16SrRNA genes:(1)Comparing the effects of different quantities of organic fertilizer input levels on soil fertility index and crop productivity,determining the optimal amount of organic fertilizer input for Shajiang black soil;(2)Comparing the effects of organic fertilizer substitute nitrogen fertilizer under equal nitrogen input on soil microbial traits,fertility index(SFI),and crop productivity,and exploring the microbial mechanisms of different proportions of combined organic-inorganic fertilizer affecting soil fertility;(3)Verifying the function of specific microorganisms and their mechanisms affecting soil fertility,and preparing long-effective and convenient agricultural commercial products.The main results of this study are as follows:(1)The results of the gradient manure treatments of the in-site field experiment showed that all organic fertilizer treatments significantly improved SFI by 15.62%～38.47%,in which FTM and TTM have the largest SFI,which were improved significantly compared to CK and CF.The factor analysis results of SFI showed that the concentrations of AP,available potassium(AK)and SOC were the main factors affecting SFI.Meanwhile,the yields of wheat and maize under TTM and FTM were the largest among the five treatments,and were significantly higher than those of CK.Considering soil fertility and economic factors,the TTM treatment is the recommended fertilization amount in Shajiang black soil.(2)The results of the combined organic-inorganic fertilizer treatments of the in-site field experiment showed that the paticipation of manure significantly improved crop yield and SFI.Abiotic factors such as soil AP and SOC concentrations and SFI,and biotic factors such as the relative abundance of Micromonosporaceae and soil bacterial community composition were the main factors affecting maize yield.Two pathways of combined manure-fertilizer treatments affecting maize yield were revealed:i)combined manure-fertilizer application improved soil AP and SOC concentrations,reduced soil C:N ratio,altered soil bacterial community composition,enhanced SFI,and then promoted maize yield;ii)combined organic-inorganic fertilizer treatments increased SOC concentration and changed bacterial community diversity,enhanced the relative abundance of Micromonosporaceae and Xanthomanadaceae,and then promoted maize yield.The results indicated that manure input is an important fertilization regime to improve the soil fertility and productivity of Shajiang black soil.The input of manure can effectively increase soil nutrient concentration,thereby promoting crop yield,while specific beneficial bacteria play a potential role in this process.(3)The results of the incubation experiment showed that medium and high concentration combined bacterial agents significantly increased the degradation rate of maize stalk and reduced soil metabolic entropy,indicating that medium concentration combined bacterial agent treatment has the best C fixation ability.The pot experiment indicated that BF treatments significantly increased wheat grain yield and aboveground biomass,and significantly improved the N uptake and use efficiency,as well as the apparent N recovery of wheat when comparing to CF.subsequently,a series of immobilized microspheres of soil improving bacterial agent were prepared,and the results showed that 160 days after the immobilized microspheres were prepared,the bacterial survival rate inside the microspheres ranged from 8.28%to 18.30%,which was greatly improved comparing to liquid TG1 and TG2 agents(0.21%and 0.53%).The pot experiment with immobilized microspheres in maize season echoed that soil AP and SOC concentrations were the main factors affecting SFI and the bactetial community of Shajiang black soil,and abiotic factors such as soil AP and SOC concentrations,SFI,C:N ratio,and biotic factors such as the relative abundance of Gemmatimonadaceae were the main factors affecting maize yield.To sum up,the specific soil improving bacterial agent can promote soil C sequestration and crop nutrient absorptions,and the maize pot expriment examined the feasibility of soil improving bacterial agents in agricultural production and verified the conclusions obtained in in-site experiments.In conclusion,combined organic-inorganic fertilizer altered soil bacterial community composition and activated specific beneficial bacterial function by regulating concentrations of soil AP and SOC as well as the C:N ratio,ultimately enchancing SFI and crop yield in Shajiang black soil.