Screening And Identification Of Phosphate Solubilizing Fungi And Development And Application Of Bacterial Fertilizer

In view of the low utilization rate of medium and low-grade phosphate rock resources,the lack of phosphorus in most cultivated soil,the low utilization rate and easy solidification of traditional fertilizer,and the destruction of cultivated soil ecological environment,it is urgent to find a new type of fertilizer with low cost,environmental protection and sustainable utilization.phosphate solubilizing bacteria fertilizer can improve the utilization rate of low-grade phosphate rock powder and traditional phosphate fertilizer,reduce the cost,on the other hand,it can dissociate the solidified phosphorus from the soil,improve the soil environment and protect the environment.In this study,three phosphate solubilizing fungi JL7、JL17 and JL32 were screened from soil samples collected from Tongren tobacco planting base in Guizhou Province,high altitude areas in Qinghai Province(near alpine grassland and Salt Lake),tropical rain forest in Wuzhishan mountain in Hainan Province,and saline alkali soil in southern Shanxi Province.The results showed that the phosphate solubilizing capacity of three phosphate solubilizing fungi in inorganic phosphorus liquid medium was264.13 mg/L,214.37 mg/L and 243.43 mg/L respectively.The colony morphology and micromorphological characteristics of JL7,JL17 and JL32 were observed,and their molecular biology,physiology and biochemistry were identified.The results showed that the three fungi JL7,JL17 and JL32 were Aspergillus fumigatiaffinis,Alternaria chlamydospora and Penicillium chrysogenum.Through single factor experiment and orthogonal experiment,the optimum conditions for JL7,JL17 and JL32 fungi to dissociate low-grade phosphate rock were explored.Under the optimum conditions,the highest phosphorus solubilizing capacity of JL7,JL17 and JL32 fungi were 967.4 mg/kg,814.5 mg/kg and 857.9 mg/kg,respectively.A pot experiment of tobacco was carried out with the fungal fertilizer made from JL7,JL17 and JL32 and the mixed fertilizer made from phosphate rock powder dissociated by three fungi.The results showed that both the bacterial fertilizer and the mixed fertilizer could significantly promote the growth of tobacco seedlings.The contents of P,K and N in soil were increased,and the contents of P,K and N in soil were increaseeed by 10.7%～26.3%,2.6%～10.3% and 6.9%～15.8% respectively;the contents of P,K and N in soil were increased by 25.4%～51.3%,1.8%～5.9% and 5.2%～9.6%respectively.At the same time,bacterial fertilizer and mixed fertilizer can also reduce soil p H.The mechanism of fungal dissociation of low-grade phosphate rock was explored by measuring the surface morphology changes of phosphate rock before and after dissociation,the relationship between the amount of phosphate and p H changes,the types of organic acids and the activity of phosphatase.Scanning electron microscope(SEM)was used to observe the surface morphology of phosphate rock powder before and after fungus dissociation.It was found that the surface roughness of phosphate rock powder before fungus dissociation was low and the structure was dense;after fungus dissociation,the surface roughness was greatly increased,the surface structure was destroyed and became loose,resulting in many pores.The results showed that the p H value of the dissociation solution of JL7,JL17 and JL32 was the lowest,which decreased to 2.9,4.1 and 3.0 respectively.It was calculated that the amount of phosphate solubilized was negatively correlated with p H,and the correlation coefficients were-0.819,-0.619 and-0.620 respectively.The organic acids secreted by the three fungi were determined by HPLC,including oxalic acid,acetic acid,fumaric acid and propionic acid.