Study On The Effect Of Compound Microbial Agents Promoting Improvement Of Saline-alkali Land By Rice

So far,the treatment of saline-alkali land has always perplexed domestic and foreign researchers.There is a huge saline-alkali land in our country.In the west of Jilin Province,soda saline-alkali soils are the most,which mainly lack nitrogen and phosphorus.In addition,long-term application of chemical fertilizers,pesticides and herbicides can destroy the soil properties,resulting in decline of fertility.And micro-environment,physical and chemical properties of soils and other microorganisms,will affect the survival of beneficial microorganisms.Therefore,it is urgent to explore the interaction between various kinds of microorganisms and develop some new bacterial fertilizers instead of chemical fertilizers.In this study,two strains of nitrogen-fixing bacteria were isolated from the soils and further identified.In addition,a strain of phosphate solubilizing fungi and a Cellulose-degrading bacteria obtained from the laboratory were studied for their tolerance to the salt and alkali.Then,different strains were mixed to prepare compound bacterial agent.The results of soil physical and chemical properties,rice morphology and physiological indexes in pot experiment were used to verify the synergistic effect of compound microbial agents with rice on the improvement of saline-alkali land.The main research results are as follows:Two strains of nitrogen-fixing bacteria were isolated from the soils and numbered as N13 and N14,respectively.N13 and N14 were preliminarily identified as Oligotrophomonas and Agrobacterium,through colony morphology,physiological and biochemical experiments and16 Sr DNA sequence analysis.The two strains of nitrogen-fixing bacteria grow well and have strong nitrogen-fixing ability.All the bacterial strains have alkali tolerance,among which the lowest tolerance was p H=10.Each bacterial strain has salt tolerance.Among them,Azotobacter N13 and N14 could tolerate 2000 mmol/ L Na Cl,and Cellulose degrading bacteria N "-1 could tolerate 1400 mmol/ L Na Cl.In addition,all bacterial strains could produce a small amount of IAA.The culture medium of two nitrogen-fixing bacteria was optimized by single factor experiment.The results showed that when soybean powder was used as the nitrogen source,sucrose was used as the carbon source,p H of the medium was 7,inoculation amount was 2%,and temperature was set at 40?,the number of viable bacteria of N13 was the highest.When soybean powder was used as nitrogen source,glucose as carbon source,p H of the medium was 6.5,inoculation amount was 2.5%,and temperature was 35?,the number of viable bacteria of N14 was the highest.Seed germination experiments showed that the simulated saline-alkali mixed solution could inhibit the germination rate,germination potential,bud length and root length of rice seeds,and The addition of compound bacteria agent could alleviate the saline-alkali stress and promote the growth of rice seeds.The results of pot experiment showed that the p H value of soil in the compound bacterial fertilizer group decreased by 0.92 units,and the electrical conductivity of the compound bacterial agent group decreased by 27.4%,compared with the control treatment.Furthermore,the contents of soil nutrients such as organic matter,available phosphorus and alkali-hydrolyzable nitrogen were increased,compared with the control treatment.The compound bacterial fertilizer group has the highest increase amplitude,but the rice growth was not good.Compared with the control treatment,the compound bacteria biochar group increased by 67.9%,113.8%,11.6% respectively,of which a large part of nutrients were used by rice growth.Compared with the control treatment,plant height,root length,fresh weight and dry weight of the compound bacterial biochar group increased by391.5%,215.5%,1201.1%,1201.4%,respectively.The SPAD,soluble protein,SOD and root activity of rice in the compound bacterial biochar group were compared with the control group,increased by 262.6%,138.2%,269.8% and 298.9% respectively,and the MDA of the compound bacterial biochar decreased by 35.6% at most.Thus,the developed compound bacterial agent has a certain improvement effect on soda saline-alkali soil,which is better than the bacteria sold in the market,and provides technical support for the restoration and improvement of soda saline-alkali soil.