The Effects And Mechanism Of Biofertilizer On Mitigation The Ammonia Volatilization From The Alkaline Soil

Biofertilizer is a new type of environmentally friendly fertilizer,which is broadly used in agricultural system to promote plant growth and as biocontrol agents.The biofertilizer is usually made from the lant growth promoting rhizobacteria and plant growth promoting fungi,which are two important microbial florae in the soil.The soil alkaline is usually correlated with the ammonia volatilization.Therefore,in this study,the effects of three different biofertilizer and traditional fertilizer on the ammonia volatilization from alkaline soil(pH 8.37-8.43,with higher ammonia volatilization than other areas)in northern China were investigated.The mechanisms of the biofertilizer regulating the ammonia volatilization were also investigated in terms of soil pH,plant absorption and nitrification.Two types of biofertilizer were applied to the alkaline soil,bacterial biofertilizer(Bacillus amyloliquefaciens and Bacillus polymyxa)and fungal biofertilizer(Trichoderma viride).By comparing the difference between the two different biofertilizer,the effects of different biofertilizer on ammonia volatilization can be shown.In addition,the effects of biofertilizer on soil microbial population and microbial structure were analyzed too using quantitative PCR and high throughput sequencing.Based on the collective results,following conclusions can be drawn:(1)The ammonia volatilization patterns in all treatments were similar.Ammonia volatilization appeared within a few days after fertilization.The rate of ammonia volatilization shown a dynamic change over the experimental period.Compared to urea(CK)treatment,ammonia volatilization in biofertilizer treatments occurred first after fertilization,along with the occurrence of maximum ammonia volatilization.Also,the period of ammonia volatilization lasted longer in the CK than that in the biofertilizer treatments.Additionally,the results showed that viable Trichoderma viride biofertilizer decreased ammonia volatilization by 42.21%compared with conventional fertilizer(CK,urea),while Bacillus amyloliquefaciens and Bacillus polymyxa decreased ammonia volatilization by 20.28%and 13.81%,respectively.(2)Soil pH,plant absorption and nitrification play important roles in soil ammonia volatilization.In this study,the mechanism of biofertilizer to reduce soil ammonia volatilization were investigated accordingly.The biofertilizer decreased the soil pH during the period of maximum ammonia volatilization,where soil pH was significantly lower in biofertilizer treatment than those of other treatments.Additionally,the biofertilizer promoted the absorption of fertilizer nitrogen by the sweet sorghum,which increased the utilization rate of fertilizer.Subsequently,the biofertilizer enhanced the nitrification by increasing the abundance of functional genes of ammonium-oxidizing archaea(AOA)and ammonium-oxidizing bacteria(AOB)rather than changing the functional bacterial community composition.(3)After the application of biofertilizer,soil microbial population and structure composition were altered.The application of Trichoderma viride biofertilizer not only increased the microbial population in soil,but also the diversity of microbial composition.Although,the application of Bacillus amyloliquefaciens and Bacillus polymyxa also increased the microbial population too,the bacterial diversity decreased.This collective results showed that types of biofertilizer may affect the microbial community in different ways.