Objectives Three kinds of microbial fertilizers, Penicillium cyclopium D12, Trichoderma harzianum and Penicillium oxalicum A1, were studied to investigate their effects on stimulating the growth of Malus hupehensis Rehd. seedlings and alleviating the soil born disease, and there by provided tools for the use of replanted apple soil.
Methods Soil was collected from an apple replanted orchard for a pot experiment, using M. hupehensis Rehd. seedlings as tested materials. The experiment included five treatments, the carrier of fertilizers (CK1), only apple replanted orchard soil (CK2), Penicillium cyclopium D12 fertilizer (T1), Trichoderma harzianum fertilizer (T2) and Penicillium oxalicum A1 fertilizer (T3). The fertilizer amount was 1.6% of the pot soil, and mixed with the soil before transplanting of seedlings. The biomass, phenolic acid content in soil, and soil microorganisms were investigated in August 2017.
Results Both the CK1 and the CK2 had no significant differences in fresh weight and dry weight. Compared with CK1 and CK2, all the treatments with the three fertilizers improved the biomass amounts of M. hupehensis Rehd. seedlings. T2 and T3 demonstrated more beneficial effects than T1 did. T2 increased the plant height, ground diameter, fresh weight and dry weigh by 53.3%, 56.0%, 40.6%, 106.3%, and T3 increased by 53.3%, 56.0%, 40.9%, 99.8%, respectively. All the three fertilizer treatments significantly improved the soil enzyme activities and bacteria population, and decreased the actinomycetes population. Compared with CK2, the neutral phosphatase activities were increased by 1.60 folds, 1.74 folds, and 1.65 folds with T1, T2 and T3 treatments, respectively; the soil bacteria population was increased by 179%, 188%, and 207%, respectively; and the gene copy number of Fusarium solani were decreased by 63.3%, 70.7%, and 73.2%, respectively. Compared with the CK2, applying the three fertilizers reduced the phenolic acid contents in soil. The contents of phlorizin and phloretin were decreased by 62.6%, 64.9%, 69.8% and 77.9%, 78.9%, 78.3%, respectively.
Conclusions The tested three microbial fertilizers show satisfactory effects in alleviating the replanted obstacles of the apple orchard soil by increasing the soil enzyme activity and bacteria population, and decreasing the gene copy number of Fusarium solani, so improving the biomass of M. hupehensis Rehd. seedlings significantly. Microbial fertilizers containing Trichoderma harzianum and Penicillium oxalicum A1 reveal better effects than Penicillium cyclopium D12.
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