Use of a Biostimulant Obtained from Slaughterhouse Sludge in a Greenhouse Tomato Crop

Currently, the use of biostimulants is widespread in sustainable agriculture because they represent an alternative to chemical fertilizers. In this manuscript, we investigate the response of a greenhouse tomato crop grown in pots to a biostimulant obtained from slaughterhouse sludge applied continuously to the substrate under which the tomato crop was grown or applied directly via the foliar route. Two doses of biostimulant (0.7 and 1.4 g L−1), applied four times throughout the crop growth period (120 days), were used. During this period, the height of the plants, number of flowers and number of fruits obtained were measured. After 90 days of the growth period, the nutrient contents in leaves as well as the chlorophyll a and b contents were analyzed. For fruits, nutrient and lycopene contents were determined, and the equatorial diameter and average fresh and dry weight were measured. The results indicate a higher content of nutrients and chlorophyll a and b in the leaves of plants treated with the highest dose of biostimulant and applied continuously to the substrate. This higher content of photosynthesis pigments in the plant is possibly responsible for a greater absorption of N by the plant and, consequently, for better growth.