Early vine harvesting of dual-purpose sweet potato (<i>ipomoea batatas</i>) increases feeding quality and total biomass without comprising tuber production

Abstract

Sweet potato is an important food crop throughout much of sub-Saharan Africa with the important attribute as a dual-purpose crop. While tuberous crops are grown for human consumption, the sweet potato can also provide substantial vine biomass suitable for feeding animals without competing for human feed resources. Sweet potato is generally low in nutrient other than carbohydrate. The newly developed orange-fleshed varieties of sweet potato, high in beta-carotene yield large quantities of vines with very little exploration of their agronomic attributes to date. Intermediate vine harvesting (ratooning) has been promoted as a strategy to further increase the value of sweet potato as a dual-purpose human/animal feed crop. The results of this practice on yields of other types of sweet potato have been equivocal or highly variable. Production effects on three new orange-fleshed dual-purpose sweet potato (Kenspot 1, SPK 013, SPK 117) developed by the International Potato Centre (CIP), of intermediate plus final (INT) versus final only (FIN) vine harvesting were assessed in a randomized block with a split plot trial. Cultivar SPK013 produced the greatest vine, tuber and total biomass yield of the three varieties tested, but also the greatest decline in tuber yields after intermediate vine harvesting. While intermediate harvesting increased vine yield in all varieties (p<0.05), in cultivar SPK013, it caused a 58% decline in tuber yield (p<0.05). The variation in performance between cultivars assessed in this study, reflects what is seen in the general literature. What is clear from the present study is that, there is a substantial interaction between environment/cultural practice and genotype. As such, it seems impossible to generalize that Intermediate vine harvesting is beneficial for vine production in the cultivars studied. It should be borne in mind that this practice may also be associated with a substantial decline in tuber yield in some cultivars. Thus, results should not be extrapolated to other varieties without investigation.