Abstract
In 1977 and 1978, the optimum yam population density and level of fertilization for a yam-maize mixture were investigated at Umudike, Eastern Nigeria. Six yam population densities (5.0, 7.5, 10.0, 12.5, 15.0 and 17.5 × 103 stands ha-1) and five fertilizer levels (0, 164, 328, 492 and 656 kg ha 1 of 9:4.5:18 N-P-K mixture) were used. The yam was Dioscorea rotundata cv. 'Obiaoturugo'; maize was planted at 33 000 stands ha-1. Intercropping reduced tuber yields (29%) and tuber size (20%) but improved land equivalent ratios LER (66%). Fertilizing at 656 kg ha 1 increased tuber yields (29%), tuber size (30%) and LER (36%). Increasing yam plant density from 5000 to 17 500 stands ha-1 increased tuber yields (147%), LER (87%) but reduced tuber size (22%). Recommended fertilizer rate and yam population density for yam-maize intercropping were 420-440 kg ha-1 and 12 500 stands ha-1, respectively.
