Fodder and tuber yields, and fodder quality of sweet potato cultivars at different maturity stages in the West African humid forest and savanna zones

A 2-year study was conducted in the West African humid forest and southern Guinea savanna zones to determine fodder and tuber yields, fodder crude protein (CP) and neutral detergent fibre concentrations, and dry matter (DM) degradation characteristics of 18 sweet potato (Ipomoea batatas) cultivars harvested at 8, 12, 16, and 20 weeks after planting (WAP). Significant (P<0.05) differences were found in fodder and tuber yields, and fodder CP and DM degradation characteristics among cultivars. Fodder yields showed both linear and non-linear trends, whilst tuber yields increased linearly in response to increasing WAP. The average CP, degradable fraction, rate of degradation, and effective degradability were relatively higher when the fodder was harvested at 12 WAP than at 20 WAP. In terms of fodder and tuber yields, and fodder quality attributes, cultivars TIS-8470, TIS-8164, TIS-87/0087, and TIS-82/0070.OP.120 could be classified to have high potential for both fodder and tuber production in both zones, whilst cultivars TIS-2534, GR-1-9-5, and TIS-82/0270.OP.13 showed low potential. The promising cultivars could be harvested between 12 and 16 WAP in the savanna zone, and 20 WAP in the humid forest zone to maximize yields of tuber and quality of fodder.