Study On The Growth Promoting Effect Of Phosphorus And Potassium Dissolving Aspergillus Niger On Soybean

Phosphorus and potassium are essential nutrients for plant growth,but most phosphorus and potassium are unusable by plants.Phosphorus and potassium dissolving microorganism can convert insoluble phosphorus and potassium into soluble phosphorus and potassium,so as to promote plant growth.They play a vital role in the transformation of insoluble and soluble phosphorus and potassium in agricultural ecosystem,environmental protection and ecological material circulation.In order to screen the fungi with the function of dissolving phosphorus and potassium,and explore the influencing factors and growth promoting effect of the function of dissolving phosphorus and potassium,this study took the phosphorus dissolving fungi as the research object,used the improved phosphorus dissolving and potassium dissolving medium to screen and domesticate the phosphorus dissolving and potassium dissolving microorganism,and optimized the medium through single factor experiment and response surface methodology.In order to explore the effect of phosphorus solubilizing and potassium solubilizing fungus Aspergillus niger Z8 on Soybean Seed Germination and seedling growth,the changes of soybean seed and seedling biomass,leaf enzyme activity,soil enzyme activity and soil microbial quantity were measured.The results are as follows:(1)Five phosphorus solubilizing fungi were screened by potassium solubilizing medium.Among them,Aspergillus niger Z8 had the highest phosphorus solubilization and potassium solubilization,which were 324.90 mg/L and 76.17 mg/L respectively.(2)The results of single factor experiment showed that the optimal medium components of Aspergillus niger Z8 were glucose as carbon source,(NH₄)₂SO₄ as nitrogen source,Mg Cl₂·6H₂O as inorganic salt and phosphorus potassium ratio of 1:3.The optimized ratio of phosphate dissolving and potassium dissolving medium optimized by response surface methodology is:glucose 9.78 g/L,Mg Cl₂·6H₂O 4.96 g/L,(NH₄)₂SO₄1.47 g/L,Ca₃(PO₄)₂5 g/L,potassium feldspar powder 15 g/L.Under this culture condition,the amount of dissolved phosphorus was 363.17 mg/L and the amount of dissolved potassium was 104.63 mg/L,which increased by 11.87%and 37.40%compared with that before optimization.The culture conditions optimized by response surface methodology were p H7,inoculation amount of 2.5%and temperature of 30?.Through the verification experiment,the measured phosphorus dissolved amount was 388.59 mg/L and potassium dissolved amount was 105.53 mg/L.this result increased the phosphorus dissolved amount by 7.00%and potassium dissolved amount by 0.86%compared with that before condition optimization.(3)Inoculation with Aspergillus Niger had no significant effect on seed germination rate,but it could increase the biomass of soybean sprouts,and the growth promoting effect of K3 treatment group was the best.Soybean sprouts were treated with different concentrations of fungal solution.The results showed that when the concentration of fungal solution was 1.0%,the plant height,fresh weight,dry weight and root length of soybean seedlings reached the maximum,the content of photosynthetic pigment in leaves of soybean seedlings was higher,and the cell volume in root tip elongation zone was the largest.(4)The results of pot experiment showed that the inoculation of Aspergillus niger increased the plant height,root length,fresh weight,dry weight,soluble sugar and soluble protein of soybean seedlings by 19.44%?33.47%,19.95%?33.50%,26.67%?86.67%,25.00%?87.50%,31.67%?47.83%and 21.70%?35.86%.(5)Different inoculation treatments increased the contents of chlorophyll(T4>T3>T2>T1>CK),superoxide dismutase(T4>T3>T1>T2>CK),catalase(T4>T3>T2>T1>CK)and peroxidase(T4>T2>T3>T1>CK).The activities of soil enzymes were detected.The order of urease content from large to small was T4>T3>T2>T1>CK,the order of invertase content from large to small was T4>T3>T2>T1>CK,and the order of catalase content from large to small was T4>T2>T3>T1>CK.(6)The content of different types of phosphatase was different in different treatment groups.The content of acid phosphatase was T2>T1>T3>T4>CK from large to small,the content of neutral phosphatase was T2>T4>T1>T3>CK from large to small,and the content of alkaline phosphatase was T4>T3>T2>T1>CK from large to small.(7)According to the statistics of the number of soil microorganisms,inoculating Aspergillus niger Z8 can increase the number of bacteria by 6.03%?32.66%,the number of fungi by 22.22%?62.22%,and the number of actinomycetes by 0.67%?20.32%.(8)In conclusion,T4 treatment group had the best effect on soybean growth promotion.Aspergillus niger Z8 has good growth promoting function and has great potential in reducing the use of chemical fertilizer and promoting the sustainable development of agriculture.