Apple replant disease (ARD) is a major factor that restricted the sustainable development of apple industry. In this study

the apple plant seedling biomass

root repiration rates

soil enzyme activities and soil environments under different phosphorus levels in continues cropping soil were determined to reveal the effect of biochar combined with phosphorus fertilizer on the control of ARD and select suitable amount of phosphate fertilizer

so as to provide theoretical basis for the renewal of old orchard and the prevention and control of ARD. Pot experiments including six treatments

which were the control (CK)

methyl bromide sterilization (F)

2% biochar (B )

2% biochar + 0.5‰ phosphate fertilizer (BP0.5)

2% biochar + 1‰ phosphate fertilizer (BP1) and 2% biochar + 2‰ phosphate fertilizer (BP2)

were carried out. The biomass and root respiration rate of Malus hupehensis Rehd. seedlings

soil nutrient and soil enzyme activity were measured by conventional methods. The results showed that methyl bromide sterilization treatment increased heights

ground diameters as well as fresh and dry weights of seedlings

which were 1.6

1.5

2.9 and 2.5 times of the seedlings in the control

respectively. The root respiratory rates and activities of protective enzymes in the F treatment were all higher than those in the control or other treatments. The treatments of B and BP0.5 both significantly enhanced heights

ground diameters

fresh and dry weights of seedlings

which were 1.2

1.1

1.6

1.4 and 1.4

1.2

2.2 and 1.9 times of the seedlings in the control

respectively. The root respiration rates increased significantly in the treatments of B and BP 0.5. Biochar combined with 0.5‰ phosphate fertilizer improved the activities of SOD

POD and CAT

and decreased the content of MDA in the seedling roots. Compared with the control

biochar combined with 0.5‰ phosphate fertilizer significantly improved the content of organic matter in soil

increased the contents of nitrate nitrogen and available phosphorus

and promoted the activities of urease

sucrase and phosphatase in soil. In conclusion

compared to the single application of biochar

application biochar combined with phosphate fertilizer could improve the development of M. hupehensis seedlings under continues cropping

increase soil organic matter content

enhance soil enzyme activity. Therefore

the integrated measures of biochar and phosphate fertilizer can better prevent and control ARD.