Investigating the ideal mixture of soil and organic compound with Bacillus sp. and Trichoderma asperellum inoculations for optimal growth and nutrient content of banana seedlings

Abstract Organic compounds from the compost of agricultural waste have been increasingly used in the formulation of substrates for fruit seedlings production. Microorganisms can enhance the beneficial effects of fertilizers on the plant, but reports on the use of endophytic strains to promote banana plant growth are rare. The goal of this study was to investigate the ideal mixture of soil and organic compound with Bacillus sp. and Trichoderma asperellum inoculations for optimal growth and nutrient content of banana seedlings. A Greenhouse experiment was arranged in a factorial scheme (3 × 2 × 2)+3, five times replicated, with the following factors: (a) substrates consisting of three organic compound and soil ratios – 20:80, 40:60, 60:40 (v/v); (b) Bacillus sp. inoculation – with [B+] and without [B-]; and (c) Trichoderma asperellum inoculation – with [T+] and without [T-]. Additionally, the following controls for substrates consisting of soil free of organic compound (0:100) were also considered: [B+T-], [B-T+], and [B-T-]. After 100 days from planting, plant height (H), pseudostem diameter (D), H/D ratio, number of leaves, total leaf area, root volume, shoot and root dry mass, net photosynthesis, and contents of chlorophyll, carotenoid, nitrogen (N), phosphorus (P) and potassium (K) were evaluated. Results showed that the substrate 40:60 with Bacillus sp. or Trichoderma asperellum inoculation provides the best morphophysiological quality to banana seedlings. The strains also showed potential to promote plant growth in different ways, either by helping phosphate solubilization or by favoring auxins and hydrolytic enzymes synthesis.