Abstract
In Puerto Rico yam (Dioscorea spp.) is usually planted in thoroughly tilled soils of the mountain region. An experiment was established in an Ultisol (aquic tropudults), a Vertisol (udic chromusterts) and an Oxisol tropeptic haplorthox) to study the effect of tillage and fertilizer rates on yield of the Binugas yam (Dioscorea alata L.). Three tillage treatments (conventional, deep and minimum) were compared to no-till; and three fertilizer levels (0, 1X and 2X the recommended level) were evaluated. The highest yields were observed in the conventionally tilled plots but differences among tillage treatments were significant only in the Ultisol and Vertisol soils. At these sites, yields under no-tillage were significantly lower than those under conventional tillage. No yield response to tillage was observed in the Oxisol, possibly because of the good physical condition of this soil. Response to fertilizer treatments was observed only in the Oxisol, a soil of low native fertility.