Yam (Dioscorea spp.) production in Puerto Rico is located in the central mountainous zone, but there is interest in expanding production to the southern semi-arid zone, where mechanization is possible, where irrigation is available and where soil pH is neutral or alkaline. Two experiments were performed during 2000 (Experiment I) and 2001 (Experiment II) in a soil corresponding to the Pozo Blanco (Fine-loamy, mixed, superactive, isohypertermic Aridic Calciustolls) series with high exchangeable potassium and magnesium contents and with a good capacity to supply nitrogen. Yam (D. alata cv. Diamante and D. rotundata cv. Guinea Negro) response to the application of nitrogen, potassium, magnesium and micronutrients was evaluated. In Experiment I, yam (cv. Diamante) yields were severely affected by an uncharacterized tuber-root rot, and marketable production varied from 5,961 to 10,742 kg/ha. In Experiment II, the disease incidence was less than in Experiment I.The application of micronutrients increased yields by as much as 100%. There was a trend for greater marketable tuber production with the application of micronutrients and 75-12-250 kg/ha (N-P-K) for cv. Diamante (18,787 kg/ha), and for cv. Guinea Negro (10,492 kg/ha), with the application of micronutrients and 75-12-0 kg/ha (N-P-K). The results suggest that with good seed-quality, micronutrient foliar applications, and moderate application rates of nitrogen and potassium, adequate yam production can be achieved in these soils.