Physiological and Economic Implications of Leaf Harvesting on Vegetative Growth and Cormel Yield of Cocoyam {Xanthosoma sagittifolium)

摘要

Cocoyam leaves contain a lot of minerals, vitamins, thiamine and proteins and are used as nutritious spinach in Ghana. The underground cormels which are the major economic part provide easily digestible starch and are often used as substitute for yamsand plantains when these become scarce in the dry season. The objectives of the investigation was to determine the effect of leaf harvest on plant growth and cormel yield of cocoyam and also to determine the appropriate age or stage of crop developmentto start leaf harvest and frequency of harvesting that will result in optimum cormel yield. The stages or times harvesting of leaves began were 12, 16 and 20 Weeks After Planting (WAP) and the frequency of harvesting were 2, 3 and 4 weekly intervals. Delayed harvesting at 20 WAP produced significantly (p<0.05) more fresh cormels than 12 WAP. Leaf harvest beginning from 20 WAP produced higher cormel yield than early harvesting at 12 and 16 WAP by 39 and 11%, respectively. Corm yield differences between the three harvesting times were not significant. Cormel and corm yield differences between frequencies of leaf harvest were also not significant. There were significant positive correlation between plant height, leaf area, number of leaves and cormel yield. The Marginal Rate of Return (MRR) of changing from harvesting at 20 WAP at 4 weekly intervals to 3 weekly intervals and subsequently to 16 WAP at 2 weekly intervals were 424 and 521%, respectively. These MRR are above the minimum acceptable rate of return and therefore the two options are more likely to be accepted by farmers.