Response of yam cultivars to staking and fertilizer application.
1989
Igwilo N.
Experiments were conducted in 1980 and 1983 to evaluate the response of yam varieties to staking and fertilizer application on a sandy loam soil located in the rain forest zone, Umudike, Nigeria. In the 1980 experiment, the variety Nwopoke (Dioscorea rotundata Poir.) was used; in 1983, 2 varieties Obia turugo (D. rotundata) and UM 680 (D. alata L.) were used. 2 levels of staking (staking vs none) and 2 levels of fertilizer treatment (0, 300 kg NPK fertilizer) were applied. The appropriate factorial combinations were arranged in a randomized complete block and replicated 3 times in 1980 and 4 times in 1983. The average seed yam weight was 300 g in 1980 and 250 g in 1983; in both years the plant population was 10,000 plants/ha. Staking increased tuber yields of the varieties in both seasons. Leaf area index (LAI) was similar in both staked and unstaked yams up to maximum LAI but thereafter unstaked plants lost their leaves and vines faster than staked plants, especially the varieties of D. rotundata. Fertilizer application increased the tuber yield of UM 680 (D. alata) in both staked and unstaked crops by increasing the LAI. Fertilizer application had no significant effect on the staked plants, Nwopoko and Obiaoturugo (D. rotundata) and reduced the yield of unstaked plants of these varieties. Varietal differences in response to staking/no staking may arise from a difference in canopy structure which, if it allows vines and leaves to contact flood water, leads to their early senescence.
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