Screening,Identification Of Indole-3-Acetic Acid Producing Strain And Its Effect On Saline-Alkali Land Improvement

Saline-alkali soil is caused by excessive accumulation of carbonate and phosphate.In saline-alkali soil,soil alkalinity and salinity rise sharply,and crop growth will be limited.Chemical fertilizers,such as calcium phosphate,urea and calcium carbonate,have been used to restore saline-alkali soil.However,the application of chemical fertilizers can reduce the number of beneficial bacteria in saline-alkali soil,further worsening the soil.In recent years,because of its characteristics of high efficiency and environmental protection by the focus of the industry,biological fertilizer application growth rapidly,but compared with chemical fertilizer there is still a certain gap,so the development of new biological fertilizer has broad prospects.In this paper,we mainly screened Indole-3-acetic acid(IAA)producing strain from saline soil,optimized the ability of the strain to produce indole-3-acetic acid,determined the functions of p H reduction,iron carrier,inorganic phosphorus solubilization,organic phosphorus solubilization,filter paper enzyme production,carboxymethyl cellulase activity related to proliferation,fermented the strain with various substrates in the optimal ratio into biofertilizer,and finally applied to potted onion and onion.Finally,it was applied to potted onion and field ferruginous onion to study the effect of biofertilizer on ferruginous onion and saline soil.The results of the study are as follows:(1)An indole-3-acetic acid producing strain,Exiguobacterium sp.A8(22.92 μg/m L),was screened by LB medium primary screening and Salkowski chromogenic solution rescreening,at optimum p H 8,optimum temperature 35℃,optimum salinity 1%,optimum carbon source maltose,optimum nitrogen source The ability of the strain to produce indole-3-acetic acid was 68.84 μg/m L at the optimum p H 8,optimum temperature 35℃,optimum salinity 1%,optimum carbon source maltose,optimum nitrogen source beef paste,and optimum carbon to nitrogen ratio 1:2.(2)It was verified that strain A8 could reduce LB liquid medium with p H 10 to p H 8.3at 24 h.The HC value(ratio of clear circle diameter to colony diameter)of iron carrier production was 1.62,the HC values of organophosphorus solubilization and inorganic phosphorus solubilization were 1.84 and 1.36,respectively,and the carboxymethylcellulase activity and filter paper enzyme activity were 1.77 U/m L and 2.99 U/m L,respectively.(3)In the pot experiment,the optimal ratio of each component of biofilm fertilizer(cow manure: wheat bran peel: straw powder: bacterial and bacterial liquid: water)was17:76:50:3:88.Under the optimal ratio,the germination rate of green onion was 71.25%.After 80 days of treatment with the optimal ratio of biofilm fertilizer,Plant height,stem diameter,stem length and root length were 58.13 cm,1.05 cm,13.63 cm and 11.3 cm,respectively.(4)In the field experiment,there were three groups(blank group CK1-no fertilizer;In the control group,CG1-cow manure 8.5 kg,wheat bran peel 38 kg,straw powder 25 kg,water 44 kg;EG1-cow manure 8.5 kg,wheat bran peel 38 kg,straw powder 25 kg,water 44 kg,bacterial solution 1.5 kg)in the experimental group.The results showed that after 100 days of adding the biological bacterial fertilizer of EG1 in the experimental group,The growth rates of plant height,stem diameter,stem length and root length of green onion were281.59%,691.43%,508.67% and 319.6%,respectively,which were 29.44%,241.43%,122.2% and 50.57% higher than that of blank group CK1.Compared with CG1 in control group,the growth rate was 29.54%,146.99%,89.13% and 21.6% higher than that in control group.Compared with CK1 in blank group and CG1 in control group,EG1 in experimental group had significantly improved plant height,stem diameter,stem length and root length.For soil nutrients and soil p H,the contents of alkali-hydrolyzed nitrogen,total phosphorus,total potassium,available phosphorus and available potassium were significantly increased after the addition of biological fertilizer of EG1 in the experimental group,and the soil p H decreased from 8.43 to 7.38.(5)Macrogenomic analysis of the inter-root soil of ferruginous onion revealed that the Chao 1 index,Faith＿pd index,and Observed＿species index of experimental group EG1 were significantly higher relative to control group CG1 and blank group CK1,and the Simpson index of experimental group EG1 was significantly lower relative to control group CG1 and blank group CK1.The species richness in the soil was greater,the species diversity was richer,the mycobiota structure of the soil in the experimental group EG1 was affected by the intervention of biofertilizer,and the dominant genera in the experimental group EG1 were Bacillus,Saccharomyces,Mycobacterium,compared with the control group CG1,blank group CK1 dominant genera were different,and PICRUSt2 analysis was used to predict the functions,and it was found that the biofertilizer of experimental group EG1 mainly had the functions of amino acid metabolism,carbohydrate metabolism and lipid metabolism,therefore,the biofertilizer of experimental group EG1 has great application prospects in the direction of saline land management.