Effect of Trichoderma fertilizer applied after disinfected with KMnO₄ on the soil microbial environment and replantation of Malus hupehensis Rehd.

Objectives  To provide the basis for preventing and controlling apple replanting disease, the Malus hupehensis Rehd., which was planted in pot with a Trichoderma fertilizer applied after disinfection with KMnO₄, was tested on the effects of the replanted soil environment and seeding growth.

Methods The pot experiment had 4 treatments, i.e. CK (old orchard soil), T1 (applied Trichoderma fertilizer), T2 (disinfected old orchard soil with KMnO₄), and T3 (Trichoderma fertilizer applied after disinfected with KMnO₄). All pots were filled up with the same soil from a 27 years old apple orchard. The biomass, antioxidant enzymes, photosynthetic parameters and soil microorganisms were determined using a real-time quantitative (q-PCR) and terminal restriction fragment length polymorphism (T-RFLP) methods.

Results Compared with the old orchard soil control (CK), the biomass amounts of M. hupehensis Rehd. seedlings were improved in the Trichoderma fertilizer (T1), disinfected old orchard soil (T2) and Trichoderma fertilizer applied after disinfection (T3), and the T3 treatment had the most significant promotion effect. The results of September showed: compared with T1 treatment, the plant height, ground diameter, fresh weight and dry weight of the T3 treatment were increased by 34.0%, 30.9%, 34.9% and 33.7%. Compared with T2 treatment, those indices were improved by 22.5%, 23.0%, 21.7% and 17.3%. Meanwhile, the root activity and the antioxidant enzymes including superoxide dismutase(SOD), peroxidase(POD), catalase(CAT) of the T3 treatment were significantly increased compared with T1 and T2 treatment. In addition, T3 treatment also optimized the soil microbial environment to a maximum extent. The absolute quantitates of Fusarium oxysporum and Fusarium proliferatum were reduced by 69.7%, 64.4% compared with the old orchard soil (CK), which were reduced by 50.0%, 49.7% in T1 treatment and 29.8%, 29.3% in T2 treatment. Principal component analysis of T-RFLP (PCA) showed that the Trichoderma fertilizer applied after disinfection (T3) significantly changed soil fungal community structure and especially reduced the apple replant disease (ARD).

Conclusions The treatment with Trichoderma fertilizer applied after disinfection by KMnO₄ significantly changed the soil fungal community structure, improved antioxidant enzymes activity, reduced amount of Fusarium oxysporum and Fusarium proliferatum, and promoted the growth of M. hupeheusis Rehd.