Response Of Soil Microbial Structure And Function To Fertilizer Management And Relationship With Carbon Storage

Straw return is one of the effective methods to improve the physical and chemical properties of agricultural soils,especially to increase soil carbon storage.Microorganisms are an important part of agroecosystems and are important for maintaining the structure and function of cropland ecosystems.In this paper,we investigated the effects of different fertilization management measures on soil physicochemical properties,microbial communities and their functional characteristics of cropland soils on the Loess Plateau using high-throughput sequencing technology,and explored the microbiological mechanisms affecting carbon storage in strawreturned cropland.The experiment included four treatments: unfertilized treatment(UC);straw return(WS);inorganic fertilizer(CF);and straw + inorganic fertilizer(WSCF).The following main results were obtained.(1)Compared with other treatments,the treatment with inorganic fertilizer application had a significant effect(P < 0.05)on cropland moisture,soil bulk density,available phosphorus and available potassium,and the treatment with straw return to the field had a significant effect(P < 0.05)on soil organic carbon.(2)Proteobacteria(about 40%)and Ascomycota(50%-80%)were the dominant soil microbial taxa,and fertilizer management had a greater effect on the fungal community(P = 0.001)compared to the bacterial community(P = 0.127).Available potassium(P < 0.05)and p H(P < 0.05)were the main drivers of bacterial and fungal community composition,and the Proteobacteria and Ascomycota were significantly and positively correlated with soil organic carbon storage(P < 0.05).Straw return was able to increase(51.74%-52.86%)the mutually beneficial symbiosis between microbial taxa.(3)Fertilizer management had a significant(P < 0.05)effect on the functional diversity of the soil microbial community.Actinobacteria and Proteobacteria contributed the most to each function.The significantly different functional enzymes by fertilizer management were glycoside transferases,carbohydrate-binding modules,and polysaccharide lyases.(P < 0.05).Straw return increased the abundance of functional genes for dissimilatory nitrate reduction and assimilatory nitrate reduction processes,inorganic fertilizer treatment increased the abundance of functional genes for nitrification,denitrification and nitrogen fixation,and fertilizer management decreased the abundance of functional genes for carbon fixation.(4)Fungal communities directly and significantly(P = 0.04)affected farmland carbon stocks,while bacterial communities assisted fungal communities with indirect effects.Mainly,the abundant taxa of bacteria Alphaproteobacteria(12%-14%)and Gammaproteobacteria(18%-21%)assisted the rare taxa of fungi Agaricostilbomycetes(0.11%-0.55%)and Wallemiomycetes(0%-0.06%)to influence soil carbon stocks.The results of the study provide a scientific basis for the stability of soil microbial ecosystems on the Loess Plateau agricultural land,and provide feasible research ideas for the enhancement of soil organic carbon in dryland rainfed agriculture in China.