ABSTRACT

Three field experiments each in two cropping seasons were conducted at the National Root Crops Research Institute (NRCRI), Umudike in southeastern Nigeria, between 2016 and 2017. The objectives ofthe study were to determine the effect of sett size and spacing on the growth and yield of Yandu white yam (Dioscorea rotundata) cultivar; to determine the effect of stake height and NPK fertilizer levels on Yandu white yam (Dioscorea rotundata) cultivar and to determine the effect of stake height and NPK (15:15:15) fertilizer on growth and yield of trifoliate yam (Dioscorea dumentorum). The three experiments were each laid out as factorial in randomized complete block design (RCBD). For each experiment, replication was thrice. Results showed that the wider spacing of Ixlm increased vine length at 3MAP in 2017 while the closer spacings of 1 x 0.25m and 1 x 0.5m increased leaf area index, tuber weight and tuber yield of the Yandu white yam cultivar mini-setts on average. The smaller 35 and 45g setts increased vine length while the larger 55 and 65g setts increased photosynthetic efficiency. The smaller 35g sett had the highest tuber yield (12.9t/ha), although the larger 55g setts gave similar results (13.lt/ha). Stakes of 2m or 3m height enhanced Yandu white yam cultivar vine length, leaf area index, photosynthetic efficiency and tuber weight on average. As mean across two seasons, staking did not significantly affect tuber yield, despite the higher yield with no staking in 2017. NPK fertilizer application did not significantly influence vine length, leaf area index, photosynthetic efficiency, tuber weight and tuber yield, but application of 200kg/ha NPK increased number oftubers per plant in 2017. NPK fertilizer did not influence trifoliate yam leaf area index, photosynthetic efficiency and tuber weight but application of a higher fertilizer rate of 450 or 600kg/ha increased vine length at 3 MAP in 2017 while 300kg/ha NPK increased number of tubers per plant in 2016. On average, application of the lower NPK fertilizer of 150kg/ha produced optimum tuber yield. The use of Im stake increased trifoliate yam vine length but staking had no effect on leaf area index, photosynthetic efficiency, number oftubers per plant, tuber weight and tuber yield.