Effects Of Fertilization On Soil Fertility And Microbial Community Structure Of Wheat And Soybean

During the last decades,the degree of agricultural intensification has continued to increase.The types and varieties of crops have been seriously reduced.The complexity of the agricultural ecosystem has been greatly reduced,and the high dependence on the use of chemical fertilizers and pesticides has seriously threatened the sustainable development of agriculture.Crop rotation is a planting method in which different crops or multiple crop combinations are planted sequentially and alternately between the years on the same field.Crop rotation achieves the purpose of maintaining soil fertility and sustainable use by increasing the crops types,especially legumes.However,domestic research on how fertilization affects soil fertility in the rotation of gramineous crops and leguminous crops is lacking.This research evaluated the impacts of long-term organic and inorganic fertilizers on soil enzyme activities,microbial community diversity and structure,seed production,and quality of winter wheat(Triticum aestivum L.)and summer soybean(Glycine max)rotation systems.First,this research studied the effect of fertilization among low fertilizer(FL),high fertilizer(FH),manure(OM),biochar(BC)and control,without fertilizer(FO)on wheat soil fertility and microbial communities.Second,the soil fertility,microbial community and soybean quality of soybean were investigated in a 27-year field study with no fertilizer control(CK)and application of nitrogen,phosphate and potassium(NPK),NPK plus straw(NPKS)and NPK plus manure(NPKM).The main research results obtained are as follows:First,organic amendment application increased total nitrogen,soil available phosphorus,and potassium compared to inorganic fertilizer and control.The activity of acid phosphatase(Ac P),?-1,4-N-acetylglucosaminidase(NAG)and phenol oxidase(Ph Ox)were generally higher in the rhizosphere than in the bulk soil.Also,organic fertilizer and biochar improved the soil acid phosphatase,phenol oxidase activity.The bulk soil and rhizosphere had the highest bacterial diversity,and the bacterial diversity was lower in wheat roots and lowest in the spikelet.Fertilization affected the relative abundance of 74 genera across 12 phyla in the above and below-ground parts of wheat.The relative abundance of Proteobacteria(Citrobacter,Pantoea,Pseudomonas,and unclassified Enterobacteriaceae)in spikelets was decreased by inorganic fertilizer,and further by manure and biochar,whereas those of Actinobacteria(Microbacterium and unclassified Microbacteriaceae)and Bacteroidetes(Hymenobacter and Chitinophagaceae)were increased.Second,the inorganic fertilizers application and the combined application of inorganic fertilizers and organic amendments(manure or straw returning to the field)improved the soil fertility,and the combined application of inorganic fertilizers and organic amendments were more effective than inorganic fertilizers alone.Compared with inorganic fertilizer,the combined application of straw and manure together with inorganic fertilizers increased soil organic matter by 34.7% and 36.24%,total nitrogen by 28.9% and 29.7%,and soybean yield by 30.8% and 29.6%,respectively.The combined application of organic and inorganic fertilizers also increased the enzyme activities of soil phenol oxidase and ?-1,4-glucosidase(BG).NPKS and NPKM significantly reduced soybean fat content by1.17% and 1.26%,respectively,without affecting soybean protein.The effects of both the inorganic fertilizers and organic amendments on the number and size of soybean nodules were not significant.Third,the long-term effects of nitrogen,phosphorus or potassium fertilizer had a significant impact on soil fertility,and the phosphorus deficiency or potassium deficiency was more obvious than nitrogen deficiency.Compared with CK,NPK and PK increased soybean yield by 22.92% and 24.22%,respectively,and increased the activity of soil acid phosphatase and phenol oxidase,but only NPK increased the ?-1,4-N-acetylglucosaminidase,?-1,4-glucosidase.Compared with CK,both NK and NPK treatments increased seed protein content by 20.16% and 20.24%,respectively.PK treatment maintained stable the content while NP treatment decreased the content.Fat contents were increased by PK,but decreased by NPK compared with CK.Fourth,there was no significant difference in bacterial and fungal diversity between bulk soil and rhizosphere.The bacterial diversity gradually decreased along the rhizosphere,root system,nodules and leaves.There was no significant difference in fungal diversity between root,nodules and leaf,whereas they were significantly lower than bulk soil and rhizosphere.Inorganic fertilizer had little effect on the abundance of bacteria,but increased the abundance of fungi.The different compartment had a significant impact on the structure of the bacterial microbial community.It gradually changed along the bulk soil,rhizosphere,root system,nodules and leaves,mainly in the relative abundance of the Thaumarchaeota,Proteobacteria and Firmicutes.The relative abundance of phylum Acidobacteria and Bacteroides gradually decreased,and fertilization had little effect on the bacterial community structure.The influence of compartment part and fertilization on fungal community structure was relatively small.In summary,the application of organic fertilizer,biochar and straw to the field improved soil biological activity,organic matter,soil fertility and crop yield.These practices enabled the wheat and soybean rotation to realize its potential increasing the stability of the agricultural ecosystem,and promote sustainable agriculture development.