Earthworm fermentation products enhance the apple replant soil environment and increase the yield and quality of apple fruit

The cultivation of apples in replanted orchards is essential given limitations in land resources. However, the presence of Fusarium and phenolic acids in the replanted soil harms the soil environment, which impedes the sustainable development of the apple industry. In this study, earthworm was used as the fermentation precursor protein to optimize the fermentation conditions, and the inhibition mechanism of the fermentation product on Fusarium and its potential to repair the apple replant soil environment were explored. Laboratory experiments showed that the optimum initial pH, temperature and time of earthworm fermentation were 7, 37 °C and 10 d, respectively. The inhibition rates of earthworm fermentation products against F. oxysporum, F. solani, F. proliferatum, and F. moniliforme were 79.8%, 75.1%, 78.7% and 79.2%, respectively. The inhibition rates of spore germination on F. oxysporum, F. solani, F. proliferatum, and F. moniliforme were 83.8%, 87.3%, 83.2% and 84.8%, respectively. In the field, use 300 mL of earthworm fermentation products for each planting pits before planting. The experimental results showed that, compared with the control, the content of soil pathogenic Fusarium and phenolic acid in Wantou (W3) were decreased by 75.1% and 59.8%, respectively, after treatment with earthworm fermentation products in 2019. Soil urease, phosphatase, sucrase and catalase activities increased by 383.2%, 78.2%, 130.3% and 43.5%, respectively. The fruit weight, anthocyanin content, soluble sugar, sugar-acid ratio, total ester ratio, total ester concentration and yield increased by 80.7%, 60.6%, 25.6%, 50.3%, 19.7%, 262.4% and 193.5%, respectively, while titratable acid content decreased by 16.9%. In conclusion, earthworm fermentation products can be used as a sustainable amendment to control apple replant disease.