Soil Microbial Biomass And Diversity Under Long-term Different Fertilization Utilizations

Long-term effects of different fertilization treatments on microbial biomass and diversity were investigated in an upland soil derived from quaternary red clay in the Red Soil Experimental Station of the Chinese Academy of Agricultural Sciences by microbial plate counting,soil microbial biomass analysis,and 16s-r DNA V3 region PCR-DGGE analysis.The results are shown as follows.1.The single application of nitrogen fertilizer(N) increased the number of cultivable fungi,compared to no fertilizer treatment(CK) and other imbalanced fertilization treatments.The number of soil bacteria of NPKS(N,P and K fertilizers plus straw incorporated) treatment was larger than that of NPK application,but to a certain extent,NPKS treatment reduced the number of soil cultivable fungi.The number of cultivable microorganisms was significantly larger in all treatments with organic fertilizer(pig manure,for short:M) than those in the treatments without organic fertilizer.The number of cultivable microorganisms in the wasteland(H) was larger than CK and all the treatments with alone inorganic fertilizer,no significant difference with all the treatments with M.The number of soil bacteria in the treatments with organic and inorganic fertilizers was larger than that with alone organic fertilizers or with alone inorganic fertilizers,but the number of fungi was less than single application of organic fertilizer(M) and larger than alone application of inorganic fertilizers,the number of actinomycetes was larger than alone application of inorganic fertilizers and no significant difference with M.The number of soil microorganisms in the treatment of wheat-soybean-sweat potato rotation receiving NPKM(NPKMR) was larger than the application of N,P,K fertilizers plus organic fertilizer(NPKM) with wheat-maize rotation.From the above results,the combined application of organic and inorganic fertilizers was better than other treatments for soil microorganisms.2.The number of denitrifying bacteria,aerobic cellulose-decomposing microorganisms and aerobic nitrogen-fixing microorganisms was larger in the treatments fertilized with M than those in the treatments without M fertilization.The treatments with imbalanced inorganic fertilizer input N,NP,NK and PK inhibited the growth of denitrifying bacteria,aerobic cellulose-decomposing microorganisms and aerobic nitrogen-fixing microorganisms,compared to CK.The treatment with fertilizer input NPKS decreased the number of three types of physiological flora (denitrifying bacteria,aerobic cellulose-decomposing microorganisms and aerobic nitrogen-fixing microorganisms),compared to NPK treatment.The number of three types of physiological flora was generally larger in the wasteland(H) than that in arable soils.The number of denitrifying bacteria was largest in single nitrogen fertilizer treatment(N).3.Soil microbial biomass C in all different treatments was 34.4-792.6μg/g,and soil microbial biomass N was 19.4-78.4μg/g.Microbial biomass C in the treatment with fertilizer input N,and microbial biomass N in the treatment with fertilizer input NK was lowest in all treatments.Microbial biomass in the waste land was highest among all the treatments.Microbial biomass was higher in the treatments with fertilized M than those in the treatments with inorganic fertilizer and CK.Microbial biomass was higher in the treatments with fertilized P than those in the treatments without P fertilizers.4.The value of soil microbes Shannon index was highest in the incremental organic and inorganic fertilizers incorporated(1.5NPK plus 1.5M) treatment,but the N treatment had the lowest value.Compared with CK,the treatment of long-term imbalanced input inorganic fertilizers reduced the value of soil microbes Shannon index.The value of Shannon index was higher in the treatments with fertilized M than those in the treatments with alone inorganic fertilizer.Long-term single application of both inorganic fertilizers and organic fertilizers would reduce diversity of bacterial community in the soil.There were no significant differences between the treatment of NPKS and the treatment with NPK.The application of P and K fertilizers would be helpful to increase the richness of soil microorganisms.In conclusion,all the treatments in this study showed a significant differences in the number of soil microorganisms,microbial biomass and microbial community diversity.Both the application of inorganic fertilizers and organic fertilizers increased soil microbial biomass.The treatments with M fertilizer also increased the richness of soil microorganisms.In contrast,the application of inorganic fertilizers reduced the richness of soil microorganisms.The application with a combination of organic and inorganic fertilizers is conductive to the stability of soil microbial community structure.