Carob seed residues - a soil organic amendment

The aim of this study was to evaluate the agricultural use of carob seed residues as a soil organic amendment and/or as a substrate. The tested crop was the tomato (Lycopersicum esculentum L., cv. Realeza). Plants were grown in pot filled with carob seed residues mixed with a sandy topsoil at the following rates (t/ha): 0; 10; 20; 30; 40; 50; 60; and 100 % of carob seeds. During the experiment, plant height, number of leaves, inflorescences, ripe fruits and the transversal and longitudinal diameter were measured weekly. Soil, carob residues and soil and carob residues mixtures were chemically analysed, in order to determine the following parameters: organic matter content, pH, electrical conductivity, N, P, K, Ca, Mg, Fe, Mn, Zn, Cu, Cd, Cr, Ni and Pb contents. Cu, Cd, Ni and Pb concentrations were determined in the carob residues only just before mixing with the sandy soil. Carob seed residues alone (used as an organic substrate) treatment promoted the highest root density, plant development, as number of leaves and fruits, and the highest crop yield. Plants of the 100% carob seed residues treatment also showed the highest density of roots. The obtained results suggest that carob seed residues may be used successfully as an organic amendment and/or as a horticultural substrate.