Microbial Community Structure And Activity In Paddy Soils And Corn Soil Aggregates Under Different Fertilization Regimes

Soil microorganisms are important to biogeochemical cycles,maintain soil fertility,inhibit plant soilborne plant diseases,and ultimately increase the crop productivity.The soil microbial community structure and function are important indicators for soil quality and productivity.Rice and corn are the major food crops in China.Fertilization is an important way to increase crop yield and has been widely applied.Exploring the response of soil microbial community structure and activity to different fertilization regimes has great significance for understanding soil geochemical cycle,guiding reasonable fertilization,maintaining soil fertility and increasing crop yield and quality.We explore the effects of long-term chemical fertilization(CF)and with straw application(SA)on soil microbial community structure(indicated by phospholipid fatty acid)and activity(community-level physiological profiles and soil enzymatic activity)at two different type rice soils(loam and silty clay)in rapeseed-rice rotation system.The main results as follow:1)Straw application treatment was beneficial to the accumulation of nutrient matter and significantly increased the contents of total carbon,total nitrogen and available potassium;2)Straw application remarkably increased the soil microbial biomass.Straw application treatment observably stimulated the growth of arbuscular mycorrhizal fungi in Jinzhou silty clay and the growth of gram positive in Wuxue loam.The contents of available potassium,total carbon and total nitrogen and temperature were major environmental factors to affect the microbial community composition in two type paddy soils;3)The utilization rates of the main carbon source in Jinzhou soils were higher than that in Wuxue soils.Soil microbial community-level physiological profiles suggested that different responses patterns to rice growth were found in straw application and chemical fertilization soils;4)The invertase and arylsulfatase activities were higher in Jinzhou soil,while urease activities were higher in Wuxue soils.Straw application significantly increased soil invertase and urease activities.Soil physicochemical factors were the main factors regulating soil enzyme activity.In core-wheat rotation system,we analyzed the distribution and activity of soil microbial community and the composition and network of bacterial and fungal community(high throughput sequencing)in three aggregate-size fractions(Macroaggregate: 2000-250 μm;Microaggregate: 250-53 μm;Silt + clay: <53μm)at Hebei sampling site soil under different fertilization regimes(Control;chemical fertilization;chemical fertilization with straw application;chemical and organic fertilization with straw application).The main results as follow:5)The contents of nutrient increased and the ratio of carbon to nitrogen decreased with increasing size of soil aggregates.The contents of nutrient in straw application treatment soil aggregates,especially in macroaggregates,remarkably higher than control and chemical fertilization treatments;6)The activities of β-glucosidase and N-acetyl glucosaminase in macroaggregates and microaggregtes were stronger than that in silt+clay.The activities of phosphatase have no significant differences among three aggregate-size fractions.Straw application treatment prominently increased the activities of β-glucosidase but decreased that of phosphatase;7)The biomass increased with increasing size of soil aggregates and straw application.The larger aggregate-size fractions were more beneficial to fungi growth.The relative abundances of copiotroph α-Proteobacteria and β-Proteobacteria were higher in larger fractions,while that of Firmicutes,Gemmatimonadetes and Crenarchaeota were opposite.Straw application treatment stimulated the growth of Actinomycetes.The relative abundances of Ascomycota decreased but that of Zygomycota increased in silt+clay;8)Both fertilizations and aggregate-size fractions significantly affected the compositions of bacterial and fungal community,but the effect of aggregate size was stronger.The changes in bacterial and fungal community were mainly controlled by the contents of carbon and nitrogen;9)The networks sizes of bacterial and fungal community were similar among three aggregate-size fractions,but the complexity increased with increasing aggregate size.There were more bacteria-bacteria interactions in larger aggregate-size fractions.We also explored the effects of four fertilization regimes(Control;chemical fertilization;organic fertilization;chemical and organic fertilization)on bacterial and fungal community compositions within different aggregate-size fractions(Macroaggregate;microaggregate;silt + clay)at Heilongjiang sampling site.The main results as follow:10)The compositions of fungal and bacterial community were significantly different across particle-size fractions and dramatically changed by long-term chemical fertilizer with/without manure additions;11)There were more Ascomycota but less Zygomycota in larger fractions.The applications of chemical fertilizers increased the relative abundances of α-Proteobacteria and Gemmatimonadetes,but decreased that of Acidobacteria;12)The fungal community was preferentially affected by soil aggregate size classes,but the bacterial community was mainly affected by fertilization managements.The changes in the compositions of fungal community were more correlated with soil carbon and nitrogen,while bacterial community was more related to soil phosphorus.Our results suggest that straw application could significantly increase the microbial biomass and activities in paddy soils and upland soil aggregates.The differences in soil environment are the main factors controlling the microbial community structure and activity.Different fertilization regimes remarkably change the microbial community structure and activity,but the changes are site-specific.