From 2007-2009, HarvestPlus and its partners conducted a biofortification program to distribute provitamin-A-rich orange sweet potato (OSP) to more than 24,000 households in Mozambique and Uganda. The goal was to determine if disseminating OSP could be an effective strategy for reducing the prevalence of vitamin A deficiency (VAD) by increasing vitamin A in local diets, especially for young children and women. Previous smaller-scale studies had shown that OSP could be an effective strategy for increasing vitamin A levels in children (von Jaarsveld et al. 2005; Low et al. 2007). This project sought to demonstrate if this strategy could be effective at a larger scale, across two countries. The project provided OSP vines to farmers as well as information about the nutritional benefits vitamin A, how to grow OSP, and how to prepare and market it. Researchers from IFPRI, HarvestPlus and CIP evaluated the impact and cost-effectiveness of the project. That evaluation found that, after two years, the project had established an adoption rate of OSP of 61-68 percent and had increased the quantity of vitamin A consumed by women and children in project households by more than two thirds (Hotz et al. 2011). Moreover, in the Uganda project areas, the rate of mild VAD fell by 9.5 percent as a result of the intervention.

Recently, collaborators from IFPRI, University of California at Davis and Nutridemics received funding from 3ie to extend the OSP study in Uganda to measure the sustainability of the intervention over time and to examine the role of social networks in fostering diffusion of OSP from the original project sites to new areas. The main research questions for this current study on “sustainability of impact” include: (i) What is the impact of the intervention eight seasons after OSP vines were originally distributed, and how have impacts changed since the conclusion of the project in season 4? (ii) How has the OSP technology diffused to other households, both within and across communities, and what factors promote expanded diffusion? (iii) How do social networks contribute to diffusion of OSP and nutrition knowledge to other households and new communities? and (iv) What does the new information about long-term outcomes, program-provided information and diffusion say about the cost-effectiveness of the original intervention?

In 2011, this team of collaborators conducted a new household survey round in the original project sites and in neighboring communities to measure the sustainability of the project and diffusion of the OSP crop and related nutrition messages. Analysis of this survey is ongoing. This project will provide rare experimental evidence of the dynamics of adoption and diffusion of an agricultural technology two years after the project has ended, and will measure the role of social networks in promoting crop diffusion and improving the cost-effectiveness of the intervention.