Microbial community in a soilless cultivation system with organic fertilization, biofertilizers and cover crop...

The growing global demand for sustainable agriculture has driven interest in biofertilizers and organic inputs as alternatives to conventional fertilization methods to counteract environmental contamination and soil deterioration. This study evaluated whether the combined use of vermicompost tea (VT), plant growth-promoting microorganisms (PGPMs), and rotational cover cropping with Mucuna pruriens could enhance the composition, activity, and functional diversity of rhizospheric microbial communities in organic soilless melon cultivation (Cucumis melo L. var. reticulatus) using vermicompost and coconut fibre substrates. Five PGPMs treatments were applied at different crop stages, including plant growth-promoting rhizobacteria (PGPR), arbuscular mycorrhizal fungi (AMF), Trichoderma (TRICH), and a combined treatment (MIX). VT batches contained high levels of nitrogen fixing bacteria (5.3-6.0 log CFU mL^-1) and phosphate solubilisers (4.6-5.2 log CFU mL^-1), contributing to microbial enrichment. PGPR and MIX treatments maintained higher total bacterial counts (>7.8 log CFU mL^-1) throughout the cycle, while AMF and TRICH increased fungal loads (>6.0 log CFU mL^-1). After the cover crop, PGPR and MIX also preserved functional microbiota levels. Enzymatic activities varied among treatments, with TRICH and MIX enhancing dehydrogenase, β-glucosidase, and acid phosphatase activities, peaking at fruit harvest. Metataxonomic analysis showed higher microbial richness in treated rhizosphere, with Proteobacteria (44.3 %) and Ascomycota (30.5 %) as dominant phyla. The legume cover crop supported microbial activity post-harvest under summer conditions. These findings underscore the value of integrating PGPMs, organic matter inputs, and cover crops in soilless horticultural systems to promote microbial health, sustainability, and productivity.