Impact Of Interaction Between Biochar And Bacteria On Cabbage Growth And Isolation And Characterization Of Benificial Microbe From Biochar Ammendmented Soil

In order to understand the impact of the interaction between biochar and soil microbes on the plant growth for exploring the mechanism of biochar improving agricultural production capacity,we detected and compared the effect of different biochar and its water-soluble components on the growth of soil beneficial microorganisms under laboratory condition,and investigated the changes of soil microbial community induced by application of biochar in soil.After that both biochar and phosphorus/potassium-solubilizing microbes were applied into the sterilized soil in the pot experiment.The interaction between biochar and soil microbe promoting crop production was studied by comparing the differences between biochar and soil microbes impacting on soil physicochemical properties and plant growth.Finally one novel strain capable of producing indoleacetic acid was isolated from the biochar amended soil.It suggested that biochar could regulate the microbial community and microbial activity through a differential impact on soil microorganism in the process of biochar improving soil.Such changes are beneficial for the construction of soil environment being conducive to crop growth and increase of soil fertility to promote crop growth and improve agricultural production efficiency.1.Previous studies have revealed that biochar could induce the disturbance of a microbial community above the family level.So far,very little is known about how individual bacteria are affected by biochar at genus or species levels.In this study,effects of biochar and its water-soluble compounds on the growth of individual soil bacteria were examined.Biochar derived from different feedstock showed disproportionate impacts on bacterial growth.Corncob derived biochar could significantly stimulate the growth of most tested strains,whereas the growth of four strains,including B.pumilus ACCC04306(Agricultural Culture Collection of China,ACCC),B.licheniformis,B.cereus and K.viridis,were inhibited by addition of rice husk derived biochar.All the tested biochars greatly supported the growth of B.mucilaginosus but inhibited that of K.viridis.More importantly,different strains exhibited discrepant growth response towards the same biochar sample,even when strains belong to the same species,suggesting that the effect of biochar on bacteria growth is strain-specific.Corncob derived biochar showed the strongest adsorption on B.thuringiensis but the greatest growth promotion was observed in B.mucilaginosus,indicating that the porous structure ofbiochar is not the sole factor that influences cell growth.Due to the possible stimulation or inhibition of water-soluble compounds existing in biochar,the growth variation of tested strains decreased or increased correspondingly when the washed biochar was applied,indicating that the water-soluble compounds in fresh biochar play an important role in cell growth and such effect is also strain-dependent.Biochar application could also enhance potassium-/phosphate-solubilizing activities through promoting bacterial growth.All these results suggested that biochar might influence bacterial growth under different mechanisms.2.In order to investigate the impact of the interaction between biochar and soil microbes on soil physicochemical properties,we compared the changes in soil physicochemical properties after application of biochar and soil microorganism in soil respectively in the pot experiments.The porous structure and adsorption capacity can give biochar an ability to improve soil.Whereas in studying the effect of biochar on the soil planted with Chinese cabbage,the application of beneficial microbes in soil supplemented with biochar could result in much more increase in soil p H although biochar lonely can improve the p H value of the soil,presumably it is due to the interaction between biochar and soil microbes.When biochar and soil microorganism were simultaneously added to the soil,the content of organic matter in soil was not only higher than that in the soil without biochar,but also higher than that in the soil only with biochar,the change of which is dose-dependent in biochar addition.It was found that biochar could promote the growing activity of the related microorganisms and increase the content of N,P and K in soil,which increased by 6.8%,45.5% and 46%respectively when compared with the control experiment without biochar.Therefore,biochar can promote the growth and activity of soil microbes in the soil,leading to the improvement in soil fertility that is beneficial for agricultural production.3.It was known that crop growth is closely related to soil fertility,and previous results showed that the interaction between biochar and microorganism in soil can improve soil fertility.Therefore,we introduced biochar and soil microorganism into the soil planted with Chinese cabbage,and investigated the growth of Chinese cabbage under different soil treatments.The results suggested that the plant height of cabbage did not change significantly no matter adding biochar or soil microorganism alone or adding both biochar and soil microorganism together.However,compared with the soil without biochar,the fresh weight of Chinese cabbage grown in the soil supplemented with biochar was increased by 13.1%,while the fresh weight of cabbage grown in the soil with both biochar and microorganism wasincreased by 14.8%.Such interaction between biochar and soil microorganism resulted in an increase by 7.7% in the fresh weight of cabbage when compared with the soil with microorganism alone,which indicated that the interaction between biochar and soil microorganism could promote the cabbage growth.Moreover,such impact of the interaction between biochar and microbe on the cabbage growth is not only related to the porous structure and adsorption of biochar,but also closely related to the water-soluble compounds in biochar.It was also found that the interaction between biochar and soil microorganism could increase by 33.3% and 1.4 folds respectively in the content of N and P in Chinese cabbage in assaying the content of N,P and K,but it had no significant effect on the content of K in Chinese cabbage.Thus the interaction between biochar and soil microbes can promote the cabbage growth and stimulate the accumulation of nitrogen and phosphorus in Chinese cabbage.4.Indoleacetic acid(IAA)can act as a phytohormone to modulate plant growth and development,thus persistent search for IAA-producing microbes is underway for a potential application in promoting plant growth.In this paper,an IAA-producing bacterium was obtained from the maize rhizosphere in biochar-amending field.This strain is a Gram-negative and facultative anaerobic rod.Phenotypic examination and 16 S r RNA gene sequencing suggested that this strain is a new strain of the Enterobacter species.We designated this strain as LX3.Strain LX3 produced up to 200 mg/L of IAA in nutrient broth and promoted barley development and increased plant chlorophyll level.This suggests that strain LX3 has potential as a biofertilizer.