AbstractA cassava trial including 20 cultivars was conducted to assess the suitability of Guyana's marginal Anira peat No. 20 and Inki clay No. 100 for this crop during a 12-mo growing period. Germplasm material was obtained from Brazil, Colombia, Mexico, Puerto Rico, and Guyana. Cultivars Tacana and Iracema (Brazil) ranked above all others on both soils, producing 28 t/ha fresh roots on the Anira peat and 24 t/ha on the Inki clay. All introduced cultivars outyielded their local counterparts. The highest yielding native cultivar, Badwoman, produced 12 and 10 t/ha of fresh roots on the Anira peat and Inki clay, respectively. Cultivar M Col 673 had the highest root dry matter content, about 40% for both soils. Edible fresh matter content (ratio of peeled to unpeeled root) averaged 0.85 and was essentially the same for all cultivars. A highly significant relationship was obtained between total plant weight and root yields on both soils (r = 0.92 and 0.94). and between harvest index and root yields (r = 0.64 and 0.81). The number of stems per cutting and stem diameter at harvest were not related to yield. However, number of edible roots per plant was highly correlated with yield (r = 0.69 and 0.54). Root thickness was also related to yield (r = 0.92 and 0.95) on both soils. Under field conditions, all cultivars stored well for 5 days before primary deterioration began.
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