INTERNATIONAL POTATO CENTER: WORLD SWEETPOTATO ATLAS
RWANDA
HISTORY AND OVERVIEW
The sweetpotato, Ipomoea batatas, preceded the potato, Solanum tuberosum, in its diffusion beyond the Americas, where it was widely grown in pre-Columbian times. Columbus brought sweetpotato with him on his return to Spain from his first voyage in 1492, eighty years before the potato reached Europe. By the 1520s, Portuguese mariners were carrying sweetpotato to ports and territories throughout Africa and Asia, a diffusion later continued by other Europeans (Huntington). The subsequent historical record of sweetpotato's introduction to Africa is somewhat unclear since the term "potato" was derived from "batata" (the Carib term for sweetpotato), so that documents of this period could be referring to either crop.
Sweetpotato soon became a significant crop in Rwanda following its introduction via Uganda in the early nineteenth century (Tardif-Douglin 1991, p. 1). Sweetpotato has been widely adopted in Rwanda, as in many relatively humid areas of Africa, due to its high yield (relative to land, labor, and time), its capacity to grow in poor soils, and its high content of carbohydrates and vitamins. Sweetpotato and beans provide the common diet of Rwandans, beans for most people being the essential source of protein, as meat is a rare luxury for most (Lenné 1991, p. 20).
Sweetpotato production has grown at a very rapid rate over the past several decades. From 1966 to 1983, the annual rate of increase in area cultivated was reported by the Food and Agriculture Organization (FAO) at seven percent, while production grew by an average annual increase of nine percent (Lenné 1991, p. 20).
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Sweetpotato Production in Rwanda
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For a note on these charts, please click here
As important as sweetpotato has been for Rwanda, production data might underestimate the extent of the crop for several reasons:
- Cultivation is widespread and small-scale, grown by most farming households on small plots of land;
- Commercial marketing of sweetpotato, a primary source of production data in many countries, has been very limited in Rwanda;
- Since sweetpotato can be left in the ground until needed, possibly for several months, there is no specific "harvest season" when yields can be estimated.
Sweetpotato has also been critically important to Rwanda's recovery from events of 1994, when a campaign of genocide (in many respects distinct from an intermittent civil war) primarily directed by the Hutu population against the Tutsi minority resulted in the death of at least 500,000 people. Roughly another two million people were displaced, either within Rwanda or to neighboring countries.
Agriculture was drastically affected, both in the short and longer terms. Overall harvest losses of all crops during this period were estimated as high as sixty percent (Scowcroft 1997, p. 31), but the disruption also affected the capacity of farmers to resume cultivation once some measure of security had been restored. Agricultural research was very drastically affected, as most of Rwanda's research scientists were either killed or driven into exile, and many facilities were destroyed.
Both sweetpotato and potato have played a major role in helping refugees maintain food security in the years after the genocide, and in helping Rwanda begin a recovery. In Kivu, across the border in the Democratic Republic of Congo (formerly Zaire), farmers intensified production of both crops, with the assistance of seed stocks received via CIP and other agricultural research centers.
According to data reported by the FAO, agricultural production has been recovering since the 1994 genocide, primarily via higher average yields of a higher concentration on non-cereal crops, especially plantain and root and tuber crops (especially sweetpotato, potato, and cassava), as indicated by the graph below.
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Production of Major Crops: Rwanda 1961 - 2004
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(All data provided by FAO, reported by weight harvested)
Sweetpotato is also being developed as a means to address one of the most serious health and nutrition problems of sub-Saharan Africa, Vitamin A deficiency. Lack of Vitamin A can weaken the immune system, leaving an individual more susceptible to deadly diseases such as measles, malaria, and diarrhea. Vitamin A deficiency is also a leading cause of visual impairment and a major risk factor for pregnant and lactating women.
The International Potato Center (CIP) is a major partner of Vitamin A for Africa (VITAA), a project intended to develop and distribute throughout several countries in sub-Saharan Africa a new series of sweetpotato cultivars which are rich in betacarotenes, used by the body to synthesize Vitamin A, and with high dry matter content and other agronomic characteristics sought by farmers (Bachou, 2002). The VITAA project is an example of biofortification, intended to develop crop varieties with increased mineral and vitamin content to enhance nutritional standards. Rwanda, given its current and potential production of sweetpotato and its nutritional needs, could likewise benefit from this initiative.
For more information, please see:
GEOGRAPHY AND PRODUCTION ZONES
Physical Geography and Climate
Rwanda is part of the Great Lakes Highland region, which also includes most of Burundi, the Kivu area of the Democratic Republic of Congo, as well as western Uganda and Tanzania bordering Lake Victoria (Tardif-Douglin 1991, p. 15). Characterized by high plateaus, long rains and short dry seasons, this region is capable of supporting intensive agriculture, and is the most densely populated extensively rural region of Africa. Rwanda can also be described as land scarce; most land considered arable is being cultivated, often very intensively.
Rwanda is a very small country; at 26,000 square kilometers, it is roughly the size of the US state of Maryland, or Connecticut and Rhode Island combined (ibid.). However, for its size the country harbors tremendous ecological diversity. Altitudes range from about 1,000 to 4,500 meters above sea level (masl), and annual rainfall varies from about 800 to 1,600 millimeters (Sperling 1997, p. 19).
Three agroclimatic regions can be defined by differences in altitude, topography, temperature and rainfall, generally across an east to west gradient, as (Tardif-Douglin 1991, p. 33):
- Low elevation zone, from roughly 800 to 1,400 masl, which characterizes much of eastern Rwanda. Cassava and peanuts are the crops best adapted to the low rainfall and high temperatures of the region, but sweetpotato and most other crops are not widely cultivated, and population density is relatively low;
- Middle elevation zone, from roughly 1,400 to 1,800 masl, best suited to most crops grown in Rwanda, ([e.g] sweetpotato, coffee, bananas, beans, and sorghum) and supporting the highest population density;
- High elevation zone, above 1,800 masl, where major crops include maize, potatoes, peas, and tea. Population density can be high in some areas, but is generally limited by the rugged terrain.
- Several maps of more specific classifications — for example by soil types, agro-ecological zones, and land use — are available from the European Digital Archive of Soil Maps, Rwanda
. Most images are digitized from paper maps, of variable clarity.
Regional Distribution of Sweetpotato Production
Sweetpotato is grown in all agroclimatic regions of Rwanda, but most heavily in the mid elevation areas, with the appropriately named Central Plateau and Granitic Ridge areas being the most important. One fifth of all Central Plateau cropland is used for sweetpotato, and yields, estimated eight tons per hectare in 1991, are much higher than the national average. Here, sweetpotato accounts for nearly a third of the calories produced by agricultural crops. (Tardif-Douglin 1991, p. 37).
Conditions in this part of Rwanda are ideal for sweetpotato in several ways (ibid.):
- Sandy loam soils relatively high in humus, light textured enough to allow root formation, and sufficiently heavy to provide structure;
- Well distributed rainfall, in the range of 750 to 1,250 millimeters (mm) with a short to moderate length dry season (roughly 60 to 95 days in the western half of the country, as opposed to 105 to 115 days in the east);
- Moderate temperatures, with extreme highs in the range of 25º to 30º C, hotter than areas of higher altitude where potato becomes a more dominant crop, but cooler than areas of lower altitude where cassava usually maintains a relative advantage.
Sweetpotato cultivation correlates not only with agroclimatic conditions, but also demographic factors. Throughout Rwanda, there has been a strong positive correlation between population density and the relative importance of sweetpotato cultivation. Although such a correlation does not indicate a priori evidence of causation, Tardif-Douglin (1991, p. 41) suggests that population density, and resulting land shortage, provides the stimulus for farmers to shift production away from lower-yielding grains toward higher yielding roots, tubers, and plantains.
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Sweetpotato Distribution in Rwanda
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For more detailed information about data sources and interpretation, please click here.
PRODUCTION SYSTEMS AND CONSTRAINTS
Cultivation
With a climate capable of supporting intensive agriculture and altitudes too high for malaria and tsetse fly infestations, most of contemporary Rwanda was densely populated even prior to the arrival of Europeans in the nineteenth century. Newly introduced crops, improvements in public health, and stable borders all contributed to a population growth rate averaging around three percent through the Belgian colonial era, lasting until independence in 1962. By 1990, Rwanda's average population density was over 290 people per square kilometer (or approximately 760 per square mile), in some areas of higher agricultural potential over twice that density. For example, in Katama, in the northwest, per capita availability of agricultural land had been reduced by 1993 to approximately 580 square meters, or one seventh of an acre (Diamond 2005, p. 321). Since sweetpotato cultivation is associated with the most densely populated areas of Rwanda, cultivation is typically on very small holdings, where one tenth to one third of the available area is devoted to sweetpotato cultivation at any time (Tardif-Douglin 1991, p. 47).
Sweetpotato is cultivated vegetatively via vines, usually from a crop just harvested by the same household. The crop is usually grown in pure stands, though sometimes in a mixed cropping system, typically with beans and maize. When mixed with other crops, sweetpotato is usually of lesser importance, often grown to maintain a regular supply of vines for subsequent planting. There is a small market in planting materials, but this is an option that most people try to avoid (ibid.).
The Agricultural Calendar
Under the conditions where sweetpotato is grown in Rwanda, the crop is flexible, and thus can be cultivated as other crops permit. This description is most characteristic of the Central Plateau, as noted above the area of greatest sweetpotato concentration.
The season of the short rains, beginning in September and lasting through November, is generally when the most important crops of maize and beans are planted, to be harvested during the subsequent short dry season, which usually lasts a little over one month. (This term can be misleading, since for the Central Plateau, the short dry season is a period of diminished rain, though not usually "dry.") The "long rains" start to become heavier in January, generally peaking in April or May. Sorghum is closely associated with this season since its long maturity does not allow it to be harvested during the short rains. A second crop of maize, beans, and other minor cereal and legume crops are often sown at this time. The long dry season, the period of least rain generally lasting from June through August, coincides with the harvest of sorghum and secondary crops of beans and maize (Tardif-Douglin 1991, p. 43).
Sweetpotato can be planted and harvested throughout the year, typically in hillside fields between September and January, and again between September and January. Households with access to flooded bottomlands can plant during the long dry season to ensure a regular supply throughout the year. In this case, the timing of operations is determined not so much by the calendar as by the need to maintain a coordinated use of both hillside and bottomland plantings, so that vines harvested from one site can be used as planting material for the other (Tardif-Douglin 1991, p. 45).
Occurrence and Control of Sweetpotato Diseases and Pests
Little information is available regarding specific pathogens or pests affecting sweetpotato in Rwanda. Sweet Potato Virus Disease Complex (SPVDC), also reported at Sweet Potato Virus Disease (SPVD), was reported as the most serious disease constraint in 1989 (Ndamage 1989, cited in Lenné 1991). SPVDC is caused by the co-infection of Sweet Potato Chlorotic Fleck Virus (SPCFV), a Carlavirus transmitted by an as yet unknown vector, and Sweetpotato Feathery Mottle Virus (SPFMV), transmitted by aphids. The duration of SPVDC in Rwanda is not precisely known, but it has been reported in Uganda at least since the 1930s, where it is also a serious constraint. Symptoms include small, distorted leaves which are often narrow and crinkled, and general stunting of plants (Kreuze et. al. 2000). Also reported in 1989 (Lenné 1991) as a serious disease constraint was Alternaria stem blight, a fungal infection probably caused by Alternaria solani.
Serious pests include sweet potato weevils (Cylas spp.) and the sweet potato butterfly (Acraea acerata), which in larval form can defoliate sweetpotato during the dry season. Weevils are described in more detail in this section of the Uganda chapter of the atlas.
VARIETIES AND SEED SYSTEMS
Sweetpotato was probably introduced to Rwanda via Uganda, where hundreds of locally occurring varieties have been identified. (Please see this section of the Uganda chapter.) It is likely that the range of varieties in Rwanda is not as great, though a comprehensive survey has apparently never been done.
The war and genocide, and subsequent migrations of millions of people, have undoubtedly had an effect on the persistence of local sweetpotato varieties, as planting material in the form of vegetative vines are very vulnerable commodities. The issue has apparently not yet been studied for sweetpotato, but has been investigated for beans (Phaseolus vulgaris L.) and potato (Solanum tuberosum). Louise Sperling (1997) found that seed stocks of beans survived in many cases better than many had feared, but that losses of potato seed tubers were very high, reflecting in part the dependence of farmers on external institutions. Variety loss of potato was not great, simply because there isn't much diversity of potato varieties, but lack of tuber seed was a major constraint to farmers attempting to reestablish crops. Finally, refugees were away from their homes typically for months, as opposed to years where war has lasted for long periods elsewhere in Africa. This could be an important factor to Rwanda's recovery, since local farmers possess local knowledge, especially important in a place as ecologically diverse as Rwanda.
The Rwandan national agricultural research institute, Institut des Sciences Agronomiques du Rwanda (ISAR) had maintained a sweetpotato improvement program prior to 1994. Surveys of farmers' fields had resulted in a collection of 315 varieties which ISAR evaluated and used in a breeding program, intended primarily to develop varieties which are high yielding, high in dry matter, early maturing, resistant to most diseases and pests, and overall well adapted to agroclimatic conditions of Rwanda. The rapid multiplication system, intended to provide Rwandan farmers a reliable source of planting material of promising varieties, was cited as a successful program which could provide a model for other countries facing similar constraints (Lenné 1991, p. 84).
CONSUMPTION, STORAGE, AND MARKETING
Consumption
Total production of sweetpotato in Rwanda was estimated at 868,204 metric tons in 2003 (FAOSTAT). The total population that year was estimated at 8,387,000 people. Both figures should be treated with caution; many people are still moving across borders, and sweetpotato production is difficult to estimate even under favorable circumstances. However, if these figures are roughly correct, then per capita sweetpotato production, hence consumption, stands at approximately 100 kilograms, not surprisingly one of the highest consumption rates in the world.
The Rwandan Government estimated in the late 1980s that sweetpotato comprised thirteen percent of the food value of the diet of rural people who then made up the vast majority of Rwanda's population, but only four percent of the food value consumed by their urban counterparts (Tardif-Douglin 1991, p. 45). At that time, the urban population of Rwanda was very low, approximately five percent of the total, but proportionately gaining. Extending that trend, but to a large extent as a consequence of the genocide, the 2003 population is estimated around eighteen percent urban (FAOSTAT). It is not known if urban Rwandans are consuming sweetpotato at a higher rate than they were twenty years ago.
Household income is also a major factor of consumption, as sweetpotato is most important in the diets of people of modest or poor means. Rural households seem to demonstrate a low "income" elasticity for sweetpotato; as incomes rise, sweetpotato's share of the diet decreases. Potatoes, on the other hand, are regarded as a prestigious food demonstrating high income elasticity (op. cit., p. 56). The poor majority of Rwanda's population might well be consuming sweetpotato at an annual per capita rate even considerably higher than 100 kilograms.
Storage
Since sweetpotato is available quite consistently throughout the year, storage has not been a major issue, although it is not unusual for farmers to practice "piecemeal harvesting," whereby roots are left in the ground until needed, possibly for several months past maturity. Constraints on this practice include damage from disease and pests, especially weevils, and the opportunity cost of taking land out of production which could be used for another planting, either of sweetpotato or another crop. This latter factor is especially important in a country where land has been very scarce.
Marketing
In 1991, when David Gregory Tardif-Douglin studied the commercial sweetpotato markets of Rwanda, he found them to be generally minimal in volume and locally constrained, but with potential to develop as the population became more urbanized. Given the tremendous disruptions that have occurred since then, the current status of the marketing system is unknown.
Prior to the genocide, Institut des Sciences Agronomiques du Rwanda (ISAR) had worked in collaboration with several international non-governmental organizations (NGOs) and international agricultural research centers (IARCs) on various research initiatives, such as higher yielding and locally adapted crop varieties and integrated pest management techniques (Buruchara et. al. 2002, p. 289). The vast majority of scientists and other staff who worked at ISAR and the Ministry of Agriculture were either killed or fled into exile. A priority of the recovery effort has been to train new staff, but given the importance of local knowledge and experience to effective agricultural research and development, the effort will take many years.
Rwanda is a member of the Regional Potato and Sweetpotato Improvement Network in Eastern and Central Africa (PRAPACE), which developed out of PRAPAC, a network established in 1982 by the national research institutions of Burundi, Rwanda and the Democratic Republic of Congo to coordinate their potato programs. Currently PRAPACE collaborates with potato and sweetpotato programs of ten countries, the other nine being: Burundi, Democratic Republic of Congo, Eritrea, Ethiopia, Kenya, Madagascar, Sudan, Tanzania, and Uganda. All are members of the Association for Strengthening Agricultural Research in Eastern and Central Africa (ASARECA). The International Potato Center (CIP) provides support in the forms of improved germplasm, scientific information, training, and administrative assistance. The United States Agency for International Development (USAID) funds the network.
The Famine Early Warning System (FEWS) posts FEWSNET, with occasional reports of food security status in several countries, including Rwanda (in English and French).
CONTRIBUTORS
Kelly Theisen is the principal contributor to the initial (2006) Rwanda chapter of the Sweetpotato Atlas.
REFERENCES
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Diamond, Jared. 2005. Collapse: How Societies Choose to Fail or Succeed. Viking Press. New York.
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Human Rights Watch. Leave None to Tell the Story: Genocide in Rwanda.
Huntington Library Plant Trivia Timeline.
Kreuze, [J.F], [R.F] Karyeija, [R.F] Gibson, [J.P.T] Valkonen. 2000. Comparisons of coat protein gene sequences show that East African isolates of Sweet Potato Feathery Mottle Virus form a genetically distinct group. Archives of Virology 145:567-574.
Lenné, Jillian. 1991. Diseases and Pests of Sweet Potato: Southeast Asia, the Pacific, and East Africa. Natural Resources Institute Bulletin No. 46. NRI. Kent, United Kingdom.
Ndamage, G. 1989. Twenty-five Years of Research into Sweet Potato from 1962 - 1987. In: Root Crops and Low-Input Agriculture. Proceedings of the Third Eastern and Southern Africa Regional Workshop on Root and Tuber Crops. Malawi, 1987. IITA. Ibadan, Nigeria.
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Sperling, Louise. 1997. The Effects of the Rwandan War on Crop Production and Varietal Diversity: A Comparison of Two Crops. Overseas Development Institute (ODI) Network Paper.
Tanganik, M.; P. Phezo; [P.T] Ewell; [N.B] Lutaladio; [G.J] Scott. 1999. The Role of Potato and Sweetpotato in Disaster Relief: The Case of Rwandan Refugees in South Kivu, Democratic Republic of the Congo (ex-Zaire), 1994-96. CIP Program Report 1997-98.
Tardiff-Douglin, [D.G] 1991. The Marketing of Sweet Potato in Rwanda: Commercializing a Perishable Crop Under Adverse Conditions. [Ph.D] Thesis, Cornell University. Ithaca, New York.