| At present,the apple replant disease?ARD?in the old orchard is becoming more and more serious.Phenolic acid compounds?mainly phloridzin?are an important cause of apple replant disease.In order to alleviate the ARD,it is important to immobilize phloridzin in soil to avoid stimulating the root system of fruit trees.Biochar is a low-cost and environmentally friendly adsorbent,which has been used to adsorb many organic and inorganic pollutants with remarkable effect.Biochar can also be used as an improver to improve the soil.Therefore,biochar is selected to adsorb phloridzin and combine with pot experiment to test the application effect.The main research contents and results are as follow:1.Biochar BC300,BC400 and BC500 were prepared at different temperature?300?,400? and 500??and characterized?FT-IR,XRD,SEM?,and phloridzin solution was adsorbed at different solid-liquid ratio for different time.BC300 has more functional groups and more stable structure,and the best removal efficiency of phloridzin was 70.50%when the solid-liquid ratio of 6 g·L-11 for 24 h.2.Phloridzin and biochar with different pyrolysis temperature were applied to the pot experiment of Malus hupehensis Rehd.seedlings.There were eight treatments:CK?CK?,phloridzin?T1?,BC300?T2?,BC400?T3?,BC500?T4?,BC300+phloridzin?T5?,BC400+phloridzin?T6?,BC500+phloridzin?T7?.Among them,phloridzin treatment significantly inhibited the growth of seedlings,the plant height,fresh weight and ground diameter were 90.62%,71.20%and 77.31%of the CK,respectively.The activities of antioxidant enzymes,soil mezymes and the number of soil microorganisms were also significantly reduced.The BC300 could alleviate the effects of phloridzin,compared with phloridzin treatment,the biomass of BC300+phloridzin?T5?was significantly increased,the activities of SOD,POD and CAT were increased by 39.94%,171.00%and 237.82%,respectively,and the MDA content decreased by 36.71%.BC300+phloridzin treatment significantly reduced the phloridzin content in soil,increased the enzymes activity,the number of culturable microorganisms and Fusarium gene copies in soil,in which the number of fungi was 50.48%of phloridzin treatment.BC300 had the best effect on the seedlings growth and the alleviated the effect of phloridzin.In conclusion,BC300 worked best on reduction of phloridzin,then we selected BC300 for the next modification,adsorption and pot experiment.3.Chitosan was selected to modify BC300 to obtain chitosan modified apple branch biochar CBC300,and the biochar was characterized?FT-IR,XRD,SEM and BET?before and after modification.After modification,more functional groups and adsorption sites were added to the biochar.Under the best experimental conditions,the removal efficiency of phloridzin by CBC300 was 90.76%.When the initial pH of the solution was 9.0,the best adsorption capacity of the two biochar can be achieved(BC300 adsorption capacity is 10.62mg·g-1,CBC300 adsorption capacity is 13.80 mg·g-1).Langmuir isotherm equation and pseudo-second-order kinetics equation can better describe the adsorption of phloridzin by two kinds of biochar.4.Modificated biochar,biochar and phloridzin were applied to the pot experiment of Malus hupehensis Rehd.seedlings.There were six treatments:CK?CK?,phloridzin?G?,BC300?BC300?,CBC300?CBC300?,BC300+phloridzin?BC300G?,CBC300+phloridzin?CBC300G?.Compared with BC300 treatment,the biomass,antioxidant enzyme activity,soil enzyme activity and soil microorganism quantity of CBC300 were increased.Compared with BC300+phloridzin treatment,the biomass,antioxidant enzyme activity and soil enzyme activity of CBC300+phloridzin treatment were increased,among which the activity of urease,intertase,phosphatase and catalase increased by 23.66%,10.78%,17.24%and 3.68%,respectively.The MDA content and the number of Fusarium gene copies were decreased.The results showed that CBC300 could effectively alleviate the stress of phloridzin on seedlings,and the effect was better than BC300. |
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