The Dual-Purpose Sweetpotato

A systemic problem faced by poor rural farmers around the world, which has the effect of exacerbating malnutrition and poverty, is one where growing human populations create increased demands on the output per unit of land for food and livestock. Intensified production systems are generally characterized by continuous cropping with few external nutrient inputs and the removal of fodder for feeding of livestock with limited recycling of nutrients and organic matter back into the soil. This essentially results in the depletion of soil nutrients and organic matter and can result in severe hardships for a great deal of rural farmers and those on whom they depend.

Recognizing the severity of this problem over 20 years ago, Dr. Carlos Leon-Velarde from the International Potato Center (CIP) realized that mixed crop-livestock systems have a crucial role to play in the bio-economical improvement of outputs for rural farmers, and that improving methods for sweetpotato cultivation could increase their ability to feed and provide nutrition for their families. Dr. Leon-Velarde and a CIP team began looking towards the sweetpotato as a potential remedial crop for these farmers because of its high productivity and low input requirements, while its usefulness for both food and feed (dual-purpose) makes it attractive in areas where land availability is declining.

This was how CIP’s work on dual-purpose sweetpotato began, and it has continued to evolve over the past 18 years. Dr. Leon-Velarde began to form a global CIP-driven team which focused on utilization rather than breeding, and as this team incorporated different management strategies of sweetpotato over the years, they began to increase the amount of foliage produced, while improving the quality of vines as an animal feed. Different cutting frequencies were tested as well as several genetic materials from the collection at CIP’s renowned Genebank, before the team managed to define an index of root to biomass to find those varieties that will maximize the production of vines while maintaining good productivity of tuberizing roots.

Sweetpotato takes approximately 150 days from planting to harvest, and if it is cropped for tubers alone, the plant will produce large amounts of roots, but leave a poor quality of fodder owing to an increment in the amount of fiber in the leaves. However, Leon-Velarde’s research reveals that if sweetpotato vines are cut 65 to 70 days after emergence, a high quality fodder can be obtained. This fodder can be stored in microsilos or given directly to livestock as feed. The roots are not affected by the cutting with the same quality crops of sweetpotato harvested as usual.

As CIP-led research into dual-purpose sweetpotato progressed, the CIP team conducted studies around Peru and the rest of the world in countries such as the Ecuador, the Dominican Republic, Vietnam, China, Indonesia, Thailand, Kenya, Uganda, and Papua New Guinea. Initially two partners were sought in each country in order to conduct tests and analyze how increased foliage could improve the bio-economic situation of farmers living in these different cultures and environments. Tests were undertaken to extract leaf proteins, which were precipitated out following boiling in hot water. This extraction was found to contain a very high concentration of proteins, which was used to feed piglets in Asia. The team then developed animal nutrition models to simulate the increment in productivity of different animal species, both ruminants and non-ruminants, as a result of using fodder obtained from dual-purpose sweetpotato cuttings.

This study started by Dr. Leon-Velarde over 18 years ago is being continued by CIP today. Research consistently demonstrates evidence to support the hypothesis that dissemination of the dual-purpose sweetpotato could help improve the livelihoods of smallholder farmers operating in mixed crop–livestock systems around the world. This research into dual-purpose sweetpotato has the potential to substantially increase the level of livelihoods of a great number of rural farmers and their families, allowing them to produce more quality fodder for animal feed and crop fertilization without harming their output yields of the sweetpotato roots.