There are high losses of N and K in humid tropical climates as a result of intense precipitation. The goal of this research project was to improve the efficiency of N and K fertilizers using high cationic exchange capacity minerals (clays). There were two phases to the project. The first one consisted of an experiment conducted in a greenhouse with treatments of urea, clay, and compost and the second, a field experiment with treatments of fertilizer and clays. In the greenhouse experiment, the concentrations of NO₃⁻ and NH₄⁺ in the leachates were analyzed during 77 d. In the field experiment, the N and P concentrations in plants and biometric measurements were quantified. The treatment with urea and clays, in the greenhouse experiment, showed slow and steady release of N; however, no significant differences among treatments were found. In all samples, NO₃⁻ concentrations were higher than NH₄⁺, due to the mobility of NO₃⁻. Significant differences (p<0.05) in the length of leaves were found in the field study; however, there were no differences in the plant nutrient contents. This indicates that there is greater nutrient absorption and plant development when using clay since less fertilizer was used but the development was the same.