Agricultural Research Case study: Reaching the end users: Vitamin A-enriched sweet potato in Uganda

25 Oct 2013

As part of the DFID Support to Agricultural Research report, Lead Commissioner John Githongo and our team visited Uganda to examine the HarvestPlus project which encouraged farmers to grow and eat Vitamin A-enriched sweet potato. The project took place over 2006-09. HarvestPlus worked with NGOs and targeted 10,000 farmers in three districts in eastern Uganda.

The project tested two different approaches, a high-intensity, two-year model (Model 1) and a lower-intensity, potentially more cost-effective approach (Model 2). In Model 1, the high-intensity agricultural advisory services and nutrition education from the first year continued into a second year. In Model 2, these activities were scaled back substantially in the second year to provide cost savings and a basis for comparing cost-effectiveness with Model 1.

The project was undertaken by HarvestPlus under its regular research programme. DFID has provided core support to HarvestPlus since 2002 and, thus, has contributed to the cost of the project.

IFPRI evaluated the impact of the project. In 2007, it conducted a baseline survey of 1,500 farmers in 84 villages. It followed this with a survey at the end of the project, two years later. It used a randomised controlled-design evaluation.[1] A qualitative study of the original households was also carried out.[2]

IFPRI’s results were positive and have been published in international scientific journals.[3] DFID used the IFPRI evidence to justify a new £30 million project with HarvestPlus (2012-15).

ICAI verification study

We conducted a survey in June 2013 to verify IFPRI’s conclusions and assess the extent to which the impact of the project has been sustained.

We randomly selected 12 of the 84 IFPRI villages and conducted focus group discussions, interviewed health officials and traders and interviewed farmers who had been in the IFPRI study. Our two teams covered six villages each and spent two days in each village in June 2013.

We corroborated many of IFPRI’s evaluation results:

  • HarvestPlus distributed Vitamin A-enriched sweet potato vines to almost all farmers in 2007. We confirmed IFPRI’s results that several farmers’ group members faced problems with the quality of the vines. Additionally, members of non-farmers’ groups reported difficulty in accessing vines and information on how to grow the new sweet potato varieties. Two years later, in 2009, 80-85% of farmers in two districts (Kamuli and Mukono) were still growing and eating the new varieties. In the third district, Bukedea, cultivation had fallen to under 40%. We confirmed that this was because farmers in Bukedea received the new sweet potato vines in the dry season. The new vines could not survive the drought and there was little left for subsequent years;
  • IFPRI indicated that 52% of Model 1 and Model 2 farmers passed cuttings from the Vitamin A-enriched sweet potatoes to other farmers within the period from July 2007 to July 2009, which increased the impact of the project. We found that between one third and one half of these farmers sold or gave away cuttings;
  • IFPRI reported increased nutritional knowledge of vitamin A sources among mothers. We found that women, representing 63% of respondents in all three districts, knew about the health and economic benefit of the Vitamin A-enriched varieties and were able to recall the names of these varieties; and
  • we confirmed IFPRI’s finding that women and children prefer the new varieties of sweet potato because they are sweeter and softer. Men prefer traditional varieties.

IFPRI also took blood samples to assess the medical impact of the Vitamin A-enriched varieties on children’s nutrition. We could not verify these findings, in the time available.[4]

Our survey took place four years after the end of the project and made it possible to assess the long-term sustainability of project benefits. We identified a number of key issues for sustainability which HarvestPlus, DFID and other implementing agencies should take into account in expanding coverage in Uganda and other countries:

  • Vitamin A-enriched sweet potato is susceptible to virus and pests. New vines need to be purchased every two to three years to maintain yield. If farmers are to continue growing these varieties, a local system is needed to ensure the supply of clean vines;
  • the new enriched varieties do not store as well as traditional varieties and need to be sold soon after harvest. Currently, market demand is insufficient and needs to be stimulated. This will require links to be established with schools and a marketing and education campaign to take place in urban areas;
  • the project could have worked closer with local government. Health service providers, the most trusted sources of nutrition information, were insufficiently involved in the project. Government health and agricultural staff are not yet sufficiently aware of the benefits for children of eating Vitamin A-enriched sweet potato; and
  • current sweet potato farming methods are degrading the productive capacity of the soil. There is a need to adopt farming methods which minimise soil disturbance and maintain soil health (such as mulching). There is also a need to diversify cropping systems to achieve sustainable increases in productivity.


For research uptake to work, researchers and development specialists need to work closely together, often for a number of years. The skills of both groups of professionals are needed, if products are to be delivered effectively to farmers and taken to scale. In this case, there was a need to involve the private sector (including local vine suppliers), as well as the public sector (including health and agricultural workers), in the process.

[1]  Farmers who had participated in Model 1 and Model 2 and those who had not been part of the project were randomly assigned to high-intensity groups, low-intensity groups and control groups, respectively.

[2] IFPRI also conducted a survey in 2011 to assess whether the positive impacts of the project were sustained. This has not been published yet.

[3] See, for example, C. Hotz  et al., A Large Scale Intervention to Introduce Beta Carotene Rich Orange Sweet Potato Was Effective in Increasing Vitamin A Intakes among Children and Women in Rural Uganda, Journal of Nutrition 142: 1871-1880, 2012 and C. Holz, Introduction of b-CaroteneRich Orange Sweet Potato in Rural Uganda Resulted in Increased Vitamin A Intakes among Children and Women and Improved Vitamin A Status among Children, Journal of Nutrition, 2012.

[4] Verifying these results would have required a longer survey with inputs from medical specialists, which was not possible in the time available.

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