Effect of biochar amendments on the growth and development of 'Vera' crisp lettuce in four soils contaminated with cadmium

Julio Rivera1*, Jhon Reyes1, Jairo Cuervo1, María Martínez-Cordón2, and Adriana Zamudio3
Cadmium is an extremely toxic heavy metal that affects agricultural lands, concentrations above 0.2 mg kg-1 in leafyvegetables is restricted for human consumption. Biochar is a promising amendment for degraded soils with low fertilityand high levels of heavy metals contamination, since it can reduce Cd2+ levels in vegetables. However, these reductionsdepend on the nature of the soil and biochar properties. This pot experiment in greenhouse conditions evaluated theeffect of biochars amendments under Cd stress conditions on lettuce (Lactuca sativa L. var. crispa L.) plants grown infour soils: Ferralsol (FS), Andosol (AS), Umbrisol (US) and Technosol (TS). Six treatments were compared: Biocharsdoses at 3, 6, 9 and 12 t ha-1, conventional fertilization (NPK) and control absolute. Biochars were obtained by slowpyrolysis from five agricultural residues: Palm empty fruit bunches (PEFBB), palm kernel (PKB), wood waste (WWB),coffee pulp (CPB) and rose stems (RSB). The CPB amendment resulted in a fresh weight plant increase of 238% to 323% in 3 to 12 t ha-1 comparing with control treatment, while WWB induced a fresh weight decrease of 90.85%. The PKB amendment presented a 20% additional fresh weight in comparison to PEFBB in Ferralsol. These results indicate that biochar positively contributes to the water status. Application of RSB at 12 t ha-1 resulted in a decrease of 50.61% in Cd concentration and a decrease of 37.4% in Cd concentration in CPB at a 12 t ha-1, both results representing promising alternatives to remediate contaminated soils. The AS+CPB and US+RSB assays showed a significant negative correlation of leaf Cd concentration when increasing biochar doses were used indicating the mitigation of the phytotoxic effect of Cd in plants.
Keywords: Biochar, cadmium phytoabsorption, cadmium stress, Lactuca sativa, slow pyrolysis, soil remediation.
1Universidad Nacional de Colombia, Facultad de Ciencias Agrarias, Carrera 30 Calle 45-03 Ciudad Universitaria, Edificio 500, Bogotá, Colombia.*Corresponding author (jucrivera@unal.edu.co).
2Universidad Nacional de Colombia, Departamento de Química, Carrera 30 Calle 45-03 Ciudad Universitaria, Edificio 451, Bogotá, Colombia.
3Universidad de Bogotá Jorge Tadeo Lozano, Centro de Bio-Sistemas, Carretera Central del Norte 3 km al norte del puente de La Caro Chía (Cundinamarca), Colombia.