Leaf yield and nutritive value of Bungu (<i>Ceratotheca sesamoides</i> endl.) and black sesame (<i>Sesamum radiatum</i> Linn.) as influenced by age at harvest in The Southern Guinea Savanna Ecological Zone of Nigeria

Abstract

Overall yield and the nutritive value of harvested leaves of bungu and black sesame at weekly interval were determined. The objective was to provide useful information for market gardeners and consumers. Field experimental plots, each 1 x 2 m in size, were laid out using 2 x 4 factorial structure in split-plot design with four replications and data collected at 7, 8, 9, and 10 weeks after planting (WAP). Detached plant leaves were subjected to proximate analysis in the laboratory. Means of two years’ results indicated that leaf and shoot yields per plant, and leaf-to-shoot ratio in the crop species were similar, but leaf and shoot yields per unit area of land were higher in black sesame (1.64kg and 5.35kg, respectively) than in bungu (0.97kg and 3.38kg, respectively). Generally, as age increased from 7 to 9 weeks, number and total length of branches, as well as number of leaves per plant also increased, and thereafter the increases were no longer significant. Leaf area per plant and leaf area index in the two crop species were similar between 7 and 9 weeks of age and thereafter declined. Based on the average of two years’ results, the highest leaf and shoot yields per plant (5.48g and 18.73g, respectively) and per m² of land (1.49kg and 5.16kg, respectively) were obtained at 9 weeks of age. In terms of the nutritive value of the leaves, the levels of crude protein and total ash in black sesame and bungu leaves, respectively, were significantly higher at 7 weeks after planting (protein: 33.68%, 34.65%; ash: 10.75%, 13.00%) than at 8 weeks (protein: 28.55%, 28.50%; ash: 8.88%, 10.88%), 9 weeks (protein: 28.33%, 28.18%; ash: 8.88%, 10.00%), and 10 weeks (protein: 28.83%, 26.08%; ash: 9.00%, 10.63%). Considering both the quantity and nutritive value of leaf yield, 8 - 9 weeks after planting the crop appears to be the optimum age to harvest the leaves of the crop species for culinary use.