Abstract
An experiment to study the effect of several rates and sources of N on the yield of Guinea Negro yam (D. rotundata) was planted in a Corozal clay (Aquic Tropodults) at the Corozal Substation in the humid region of Puerto Rico. The experiment consisted of 10 treatments replicated five times in a partially balanced incomplete block design. Treatments included sulphur-coated urea (SCU 36% N), ammonium sulphate (20.5% N) and urea (46% N) as the N sources at 224, 336 and 448 kg/ha. All plots except the control received 49, 372, and 90 kg/ha of P, K, and Mg, respectively, 2 and 5 months after planting. No significant differences were observed among treatments. An average of 46.24 t/ha was recorded, a yield which is considered good. Data from this study indicate that under the existing conditions, there was no need to apply different N sources and quantities. This soil initially has sufficient quantities of available nutrients for good yam production.