ABSTRACT
The effects of irrigation frequency, plant density and nitrogen fertilization on the productivity, mean weight, length and diameter of yam (Dioscorea cayennensis L.) tubers were evaluated. The experiment was conducted in João Pessoa, Paraíba State, Brazil, in a Red-Yellow Podzolic soil of sandy texture, during 1988-89 and 1989-90. Three irrigation frequencies corresponding to 40-60, 60-80 and 80-100% of available water for plants, two plant densities (10.417 and 15.625 plants.ha-1) and four nitrogen levels (0, 50, 100 and 150kg.ha-1) in split-split plot were tested. The irrigation water was applied from the beginning of the vegetative phase (90 days after planting) until the end of flowering (2l0 days after planting). The plant density influenced significatively the yam productivity and the density of 15.625 plants.ha-1 presented the best results. Maximum yield and mean weight of yam tubers were obtained with approximately 90kg.ha-1 of nitrogen. The water level corresponding to 70% of available water for plants, gave satisfactory results of vegetative development and productivity.
Key words:
Dioscorea cayennensis; available water; water level; spacing