Martínez, M.B. and Lugo-López, M.A. 1953. Tillage tests: II, the beneficial effect of subsoil fertilization on sugarcane yields. The Journal of Agriculture of the University of Puerto Rico. 37, 1 (Jan. 1953), 35–43. DOI:https://doi.org/10.46429/jaupr.v37i1.12775.