Substrate biofortification in combination with foliar sprays of plant growth promoting bacteria and humic substances boosts production of organic tomatoes

Global demand for organic produce has increased by ca. 20% annually as consumers express increasing concerns over pesticide residues in their food. Organic tomato farming under tropical conditions is limited, and studies of production for industrial processing are relatively rare. In this study, we aimed to evaluate a new biotechnological tool with the potential to accelerate the conversion from conventional to organic industrial tomato production by combining the benefits of (i) the plant growth-promoting bacteria (PGPB) Herbaspirillum seropedicae and (ii) humates. This novel biofertilizer was first applied in plant growth substrate to stimulate seedling growth under greenhouse conditions; subsequently, it was used as a foliar spray following the transplantation of greenhouse seedlings to field conditions. The benefits of vermicompost plus PGPB and humate were evident in both seedling growth and development. Fruit biomass increased significantly relative to control plants after changes in plant metabolism during early growth stages. After transplantation to the field, foliar spraying of PGPB and humates enhanced nitrate uptake and nitrate reductase activity; it also stimulated the secondary metabolic phenylalanine ammonia lyase pathway. This new generation of biological products based on vermicompost, soluble organic matter and selected beneficial microorganisms provides opportunities for effectively increasing biological inputs to sustainable food, fiber and energy production. (C) 2014 Elsevier B.V. All rights reserved.