Assessment of organic substrates derived from marine and food waste for the growth of tomato plants

The cultivation of Tomato (Solanum lycopersicum L.) involves large extensions of soil or greenhouses, which in recent decades has been reduced due to problems such as erosion. An alternative that has been found to maintain crop yields is the use of culture media and hydroponic systems. Taking into account the problem with the amount of marine and food residues, as well as the rising demand for alternative crop substrates to achieve sustainable and ecological agriculture, the objective of this study was to evaluate different growing substrates obtained from the valorization of residues suitable for the development of tomato. For this purpose, a physicochemical characterization (pH, electrical conductivity, porosity, bulk density, organic matter content, and elemental analysis) of the following substrates was carried out: i) 50% peat+50% vermiculite as the control treatment, ii) 50% compost+50% vermiculite, and iii) 50% Posidonia oceanica+50% vermiculite. Subsequently, the development of tomato plants was carried out for 21 days in a greenhouse, and morphological and nutritional parameters were evaluated. Regarding the physical parameters, it should be noted that the Posidonia oceanica plants showed slower growth and a stem length of 30 cm, shorter than the 43 cm of the control and the 45 cm of the peat. However, in terms of nutrition, Posidonia oceanica showed the best values in terms of chlorophyll concentration. The concentration was higher in the samples developed in Posidonia oceanica, reaching a value of 45 mg/kg, followed by the compost (30 mg/kg) and the control (25 mg/kg). Finally, it was observed that Posidonia oceanica was the substrate with the highest percentage of the macronutrients Ca, Mg, K, and Na, as well as in the micronutrients Fe, Cu, Zn, B, and Si. Both the compost from food wastes and Posidonia oceanica treatments were demonstrated to be suitable components for use as agricultural substrates.