Development And Application Of Bacterial Fertilizer For Apple Replant Disease

In this study,seven Bacillus strains QSB-6（Bacillus amyloliquefaciens）,HSB-2（Bacillus vallismortis）,XNRB-3（Bacillus licheniformis）,XC1（Bacillus velezensis）,2RS-9（Bacillus siamensis）,4R-5（Bacillus subtilis）and 9R-5（Bacillus atrophaeus）which have strong antagonistic effects on the main pathogens of apple replantation were screened by plate confrontation antagonism test.Seven strains were combined and found to be compatible with each other and could be cultured together.On the basis of optimizing fermentation conditions,bacterial fertilizer was developed and the effect of preventing and controlling apple continuous cropping obstacles was verified.Hereinafter referred to as bacterial fertilizer.The experiment consisted of five treatments:replanted soil（CK1）,replanted soil fumigated with methyl bromide（CK2）,replanted soil treated with blank microbial fertilizer carrier（T1）,replanted soil treated with Bacillus velezensis（T2）,and replanted soil treated with bacterial fertilizer（T3）.The main test results are as follows:1.The antagonistic bacteria were compounded according to a volume ratio of 1:1 to make a compound bacterial solution.Subsequently,single factor and orthogonal experiments were used to select and optimize the fermentation medium and fermentation conditions.The optimal fermentation conditions were peptone 10.00 g·L^-1,ammonium chloride 5.00 g·L^-1,maltose 20.00 g·L^-1,rotation speed 180 r/min,temperature 30℃,inoculation amount 5%,and p H 7.2.After applying bacterial fertilizer,the biomass of Malus hupehensis Rehd.Seedlings was significantly increased.In August,the plant height and ground diameter of bacterial fertilizer（T3）were increased by 1.80 times and 1.64 times respectively compared with replanted soil（CK1）.The fresh and dry weight of aboveground parts increased by 3.13 and4.07 times,respectively;the underground fresh and dry weight increased 2.93 times and 3.98times respectively.3.After applying bacterial fertilizer,the root configuration of M.hupehensis Rehd.Seedlings changed significantly.The data in August showed that total length of roots,root surface area,and the number of root tips and forks of the seedlings treated with bacterial fertilizer（T3）were 2.77,2.21,2.76 and 4.34 times of those of the replanted soil（CK1）,respectively.Compared with the continuous cropping control（CK1）,the soil treated with Bacillus velezensis（T2）and the bacterial fertilizer（T3）treatment group showed a significant increase in root enzyme activity and a significant decrease in MDA content in M.hupehensis Rehd.Seedlings.For example,the bacterial fertilizer（T3）treatment increased SOD,POD and CAT by 31.75%,173.51%and 87.79%,respectively,while MDA decreased by 38.65%.4.The bacterial fertilizer improves the main enzyme activity of the soil.The soil enzyme activity of bacterial fertilizer（T3）was the highest,followed by Bacillus velezensis（T2）.Taking the data in August as an example,the activities of invertase,urease and phosphatase of the bacterial fertilizer（T3）were 1.66 times,2.56 times and 1.75 times that of the replanted soil（CK1）,respectively.5.After applying bacterial fertilizer,the number of culturable bacteria increased significantly,the number of culturable fungi decreased.After the application of bacterial fertilizer,the relative abundance of fungal communities in soil was different.The gene copies of four Fusarium sp.decreased to varying degrees,and the decrease was 45.81%-77.94%.The relative abundance of Fusarium sp.was significantly reduced.Compared with the replanted soil（CK1）,the bacterial fertilizer（T3）decreased by 68.87%,and the effect of bacterial fertilizer（T3）on reducing the relative abundance of Fusarium sp.was better than that of replanted soil fumigated with methyl bromide（CK2）.6.The results of field tests in Laizhou,Qixia and Yiyuan showed that after applying bacterial fertilizer,the plant height,ground diameter and branch length of apple saplings increased to a certain extent,while the replanted soil（CK1）showed little difference compared with the blank microbial fertilizer carrier（T1）,which was consistent with the trend of pot experiment results.Among the different treatments,the invertase activity,urease activity and phosphatase activity of the three places were the highest in bacterial fertilizer（T3）.The number of culturable bacteria in the soil increased significantly,while the number of culturable fungi decreased.