Microbial Mechanism Of Biochar Alleviating The Apple Replant Disease And Application Of Modified Biochar

Apple replant disease(ARD)also known as replanting disease,it refers to the abnormal crop growth caused by the continuous cultivation of related or the same crops on the same soil.Generally,it is shown that the yield of crops is reduced,the quality is deteriorated and the growth and development are stunted.There are many reasons leading to ARD,including the change of microbial community structure in the soil,the accumulation of toxic substances,the aggravation of diseases and insect pests,and the deterioration of soil physical and chemical properties.The occurrence of ARD is related to soil properties,replant times and other factors,and the subsequent improper management of water and fertilizer will aggravate ARD.At present,the ARD is becoming increasingly serious.A large number of studies have shown that the change of microbial community structure is the significant cause of the apple replant disease.Therefore,it is of great significance to change the soil microbial community structure to reduce ARD.This experiment is carried out on the basis of the experiment of this research group.The main research contents and results are as follows:1.Biochar at different temperatures was applied to the soil treated with Phlorizin to explore the effect of biochar on soil microbial mechanism.A total of 8 treatments were set in the experiment: Control(CK),phlorizin treatment(P),300 biochar treatment(300B),400 biochar treatment(400B),500 biochar treatment(500B),300 biochar + phlorizin treatment(300BP),400 biochar + phlorizin treatment(400BP),500 biochar + phlorizin treatment(500BP).The results showed that the total number of bacterial and fungal species in the soil treated by 300 B was less,the diversity of bacteria were lower,and the diversity of fungi were higher.This suggested the presence of a large number of dominant bacteria,they increase the metabolic activity of the carbon source,improve the soil environment,enhance the stress resistance of plants,and promote the healthy growth of crops.The increase in the abundance of these dominant microflora is mainly due to the changes in the soil environment after the addition of biochar into the replant soil.That is,adding 300 B to the soil is the best treatment effect.Therefore,300 B was modified and applied in the pot experiment.2.The modified biochar 300 CB was obtained after the modification of 300 B with chitosan.replant soil was treated with biochar(300B),modified biochar(300CB)and methyl bromide.they were used in pot experiment,and the Malus hupehensis Rehd.seedlings were used as materials.A total of 4 treatments were set,the results showed that compared with300 B treatment,the soil microbial quantity,biomass,leaf antioxidant enzyme activity,soil enzyme activity and soil nutrients were increased in 300 CB treatment,while the content of MDA and phenolic acids were decreased.Compared with the replant soil control,the plant height,ground diameter,fresh weight and dry weight after 300 CB treatment increased by53.1 %,20.4 %,78.9 % and 79.2 %,respectively;SOD activity increased by 31.1 %;MDA content significantly decreased by 24.2 %;The number of bacteria and actinomycetes increased by 34.8 % and 65.8 %,respectively;while the number of fungi decreased by35.8 %;The urease activity,sucrase activity,phosphatase activity and catalase activity were increased by 93.1 %,40.4 %,22.1 % and 71.3 % respectively;The contents of available phosphorus,nitrate nitrogen,available potassium,ammonium nitrogen and organic matter increased by 114.0 %,91.9 %,32.5 %,78.5 % and 159.4 %,respectively.The content of phloretin was reduced by 40 %.In conclusion,300 CB can effectively alleviate the apple replant disease,and its effect is better than 300 B.