Composting of fresh vegetable residues and its application in lettuce cultivation

ABSTRACT A considerable part of fresh plant-based food has been discarded as waste, although it could be used to make organic compost for growing plants, retaining nutrient that would be discarded without any control in the environment. The aim of this study was to produce an organic compost using fresh vegetable food discarded from restaurants and mowed grass and to evaluate it for production of lettuce. The compost was produced and mixed with the commercial substrate Tropstrato HT Hortaliças® to occupy 0, 5, 10, 15, 20 or 25% of the volume of the mixture, which was used to grow Imperial and Imperial Roxa cultivars in the first experiment, and Camila and Red Star lettuce cultivars in the second one. The experiments were conducted under protected environment, organized in a 6x2 factorial scheme, following completely randomized design with three replicates. Chemical analyses of the substrate and compost and measurements of plant size and mass were carried out. The addition of compost caused an increase in all measurements of the plant traits, with the maximum estimated increase ranging from 1.7 to 9.0 times that estimated for the absence of compost in the plant growth substrate. Maximum estimated values for size and mass were observed with compost concentrations ranging from 20.1 to 26.7% of the mixture volume. The production of organic compost and its mixture with a commercial substrate proved to be an alternative for lettuce production, giving a better destination to the organic residues and promoting a reduction in the use of industrial inputs.