Impact Of Microbial Inoculants On Microbial Quantity And Enzymatic Activity In Paddy Soil

The experiment was conducted to study the impact of microbial fertilizers on the quantity of different microorganisms, enzyme activity, microbial biomass and available nutrient contents in paddy soil, compared with no microbial fertilization, in Harbin, Heilongjiang, China. The results showed:(1) Both DMF(Double M microbial fertilizer) and SPA(Soil phosphorus activator) were able to increase the quantity of soil bacteria, and two kinds of fertilizer generated synergy, making the quantity of soil bacteria highest under A3P2 treatment.The application of DMF reduced the number of fungi, but the application of SPA increased the quantity of fungi in soil with the maximum number of soil fungi under P2 treatment. The combination of the two kinds of microbial fertilizers increased the number of fungi but SPA had more significant effect when used alone.DMF increased the quantity of soil actinomycetes remarkably and SPA increased the number of actinomycetes also. After two kinds of microbial fertilizers combined together, they increased the number of soil actinomycetes, with the largest number of soil actinomycetes under treatment of A3P2.(2) Applying DMF increased urease activity over the growing season except at the mature stage with the highest urease activity under treatment A3. The application of SPA could increase the urease activity but the effect was not as significantly as DMF.Both DMF and SPA were able to increase the sucrase activity in soil with the best effect under treatment A1 and P1. The effect of applying SPA was more significant than applying DMF. The combination of two kinds of fertilizers had the greatest influence on invertase activity under treatment A3P2.Three kinds of fertilizations had limited effects on soil acid phosphatase activity at tillering, heading and heading stages, but the effect was significant at the mature stage. And as the microbial fertilizer application rate increased, the soil acid phosphatase activity was enhanced. The influence of SPA was more significant than that of DMF, which was more significant than that of the combination of the two kinds of microbial fertilizers.(3) Both DMF and SPA could increase microbial biomass C, and DMF had most significant effect at mature stage, with the quantity of soil bacteria highest under A3 treatment. SPA increased microbial biomass C at heading and mature stages with the maximum microbial biomass C under P2 treatment, and the effect of applying DMF was more obvious. Two kinds of microbial fertilizers used together had the optimum result under A3P1 treatment.Applying DMF could increase microbial biomass N with the largest effect under A3 treatment, however SPA could increase more microbial biomass N than DMF. The combination of two kinds of microbial fertilizers increased biomass N and reached the best result under A3P2 treatment.(4) Applying DMF could improve soil alkali-hydrolysable N content, the maximum was on A3 at heading stage, but it got its maximum under A2 treatment at other three stages. The application of SPA also increased soil alkali-hydrolysable N content at tillering and heading stages under P1 treatment Two microbial fertilizer combination produced synergies, which improved their effect each other.DMF achieved the highest content of soil available P under A1, but the optimal fertilizer treatment was A2 at heading stage. The combination of two kinds of microbial fertilizers had more effect on soil available P content than they were used separately.DMF could significantly increase soil available K content and the optimum fertilization rate was A1 treatment. SPA could not improve soil available K content significantly and the combination of two kinds of fertilizers had lower soil available K content than DMF applied alone.