Abstract
Two experiments were established 1 May through 1 December 1991 and 1992 to determine the monthly nutrient uptake and dry matter production of the 'Gunung' yam (Dioscorea alata) grown on an Ultisol. During the first year the plants were fertilized with 0; 667; 1,333; 2,000 and 2,667 kg/ha of a 15-5- 15-5 (N, P2O5, K2O and MgO) fertilizer supplemented with a minor element mixture. No fertilizer was applied the second year. Biomass harvests were conducted at 2, 3, 4, 5, 6 and 7 months after planting. At each harvest, the plants were dug-up and separated into leaf-laminas, vine and petioles, roots and tubers. Fresh and oven-dry weights of the plant components were determined and samples from each were analyzed for N, P, K, Ca and Mg. Regardless of the year, tuber dry matter yield was not significantly affected by the fertilizer treatment. Maximum nutrient uptakes were 214 kg/ha of N, 19 kg/ha of P, 223 kg/ha of K, 95 kg/ha of Ca and 9 kg/ha of Mg. Nitrogen, K and Ca uptake peaks occurred about five months after planting. Maximum dry matter production was 11,303 kg/ha, 8,672 kg/ha of which was tuber dry weight. The dry matter production peak occurred at the completion of the 7-month cropping cycle. The plants utilized 24.7 kg/ha of N, 2.2 kg/ha of P, 25.7 kg/ha of K, 11.0 kg/ha of Ca and 1.0 kg/ha of Mg, for every 1,000 kg/ha of edible dry matter produced.