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Low-Cost Storage of Fresh Sweet Potatoes in Uganda: Lessons from Participatory and On-Station Approaches to Technology Choice and Adaptive Testing
Abstract
Studies were undertaken to identify and test low-cost storage technology for fresh sweet potatoes and subsequently to apply this technology in the northern region of Uganda. In this region the emergence of cassava mosaic disease has made the technology relevant to the rural food system due to the need to extend the availability of sweet potatoes. The studies used a combination of on-station and on-farm trials to test the technical feasibility and social compatibility of low-cost storage technologies. The performance of the storage methods and the process by which technical options were chosen, developed and tested are discussed. It was found that, although the on-station trials provided broad guidelines for technology development, specific requirements needed to be devised in conjunction with farmers. The use of parallel on-station and on-farm trials, although partially contradictory, saved much time and hastened the technology-validation process.
... This is critical in the months of May to June, because these are months of high harvests. However, farmers only have access to baskets, sacks and cut plastic vessels such as jelly cans 42 . ...
... Long-term storage of fresh roots has been attempted on an experimental basis in Soroti, in the mid Northeastern region of Uganda, with the participation of local farmers using below-ground pits, above-ground clamps with conical thatched roofs, and wooden boxes kept indoors 42 . Ash and other materials have also been used to extend storage life An optimal mix of storage techniques and cultivars is necessary to store fresh sweetpotatoes for up to three months, or long enough to make a difference when local food security is most uncertain 42 . ...
... Long-term storage of fresh roots has been attempted on an experimental basis in Soroti, in the mid Northeastern region of Uganda, with the participation of local farmers using below-ground pits, above-ground clamps with conical thatched roofs, and wooden boxes kept indoors 42 . Ash and other materials have also been used to extend storage life An optimal mix of storage techniques and cultivars is necessary to store fresh sweetpotatoes for up to three months, or long enough to make a difference when local food security is most uncertain 42 . ...
Sweetpotato (Ipomea batatas) is a versatile crop that serves the roles of food and nutrition security, cash crop in both raw and processed forms. It is a source of livestock feed and has great potential as a raw material for industrial processing. The potential of sweetpotato has been greatly underexploited by the fact that it has been regarded as a poor man’s food and is mainly grown under marginal conditions for subsistence by most producers, who are rural small-scale farmers in developing countries, such as Kenya and Uganda. Losses in the highly perishable root crop and its leaves are exacerbated by lack of appropriate postharvest knowledge, technologies and facilities. Inadequate information on available cultivars also limits the maximum utilization of the crop and leaves. The current review examines production potential, postharvest handling practices, marketing, and physicochemical and nutritional properties of sweetpotatoes.
... If farmers could store fresh roots they could benefit from higher prices at the end of the harvest season. In practice there is little use of pits, clamps (mounds of sweetpotato sealed with earth to maintain humidity and keep out pests) or other types of stores in SSA; Malawi is an exception, although these are used in other parts of the world (Hall and Devereau, 2000). Research by the Natural Resources Institute (NRI) on low cost storage using pits and clamps with thatched roofs showed that storage up to 4 months is possible. ...
... Research by the Natural Resources Institute (NRI) on low cost storage using pits and clamps with thatched roofs showed that storage up to 4 months is possible. Stored roots are fit for home consumption but sell with a price penalty or may not be marketable because they lack the "just from the garden look" which consumers expect in fresh products (Hall and Devereau, 2000). Low cost storage was validated by NRI in Tanzania. ...
... Curing sweetpotato roots at about 29ºC with high humidity for four-seven days prior to storing at 12-14ºC is used commercially in the United States to heal wounds, protect against disease, reduce shrinkage and extend storage (Kemble 2004). High ambient temperatures may mean that this type of curing is not applicable in SSA (Hall and Devereau, 2000). NRI has tested pre-harvest curing by removing sweetpotato foliage 14 days before harvesting, which reduced post harvest losses by up to 40% (RIU 2007). ...
... However, there are some simple methods used to increase their storability that can be used in conjunction with other storage methods (Hall and Devereau, 2000). Drying help to remove moisture, reduces bacterial growth, and inactivates metabolic processes and enzymatic decomposition. ...
... To minimize losses due to respiration, a ventilation shaft can be added. Results are fairly poor with this technique and estimated storage time is 2-3 months (Hall and Devereau, 2000). ...
... Sweet potato is a highly delicate and easily damaged crop which is very difficult to store for a long period of time [14]. Those in sales of sweet potato in Plateau State usually handle fresh sweet potato and are often faced with the challenge of proper storage due to its high moisture content. ...
Spoilage of sweet potato could be enormous when inadequate methods of storage are used. This research investigated impact of methods of storage on spoilage of sweet potato in three major markets of Plateau State Nigeria. Data for the study were obtained from sellers of sweet potato in Yan Doya market, New market and Farin Gada market of Plateau State through administration of questionnaires. Analysis of the data was carried out using descriptive statistics, Pearson Product Moment Correlation (PPMC), F-test statistics, t-test and Multiple Linear Regression (MLR) with backward elimination procedure. Results from descriptive statistics showed that majority of sweet potato sellers adopted use of sack for storage of their goods. The second method commonly used for storage of sweet potato in the study area was found to be root cellar method. Pair-wise application of PPMC indicated that spoilage of sweet potato was positively correlated with adopted methods of storage which suggested existence of relationship among the variables. Analysis using F-test statistics indicated that the relationship did not occur by chance between the variables hence t-test aided determination of which independent variables mainly influenced the dependent variable of the study. From the use of MLR with backward elimination procedure, spoilages from sacks and root cellars methods were the independent variables which mainly influenced the total spoilage of sweet potato in Plateau State Nigeria. Therefore, policy holders in Plateau State need to offer agricultural extension services that would provide modern storage facilities or educate sellers of sweet potato on best way to use both basket and root cellar methods which were their adopted methods commonly used for storage of sweet potato.
... Adoption of the sand storage and sprouting technology is a viable option of preserving genotypes in dry prone areas and as a source of planting material. Storing sweetpotato roots in the soil is not new to smallholder farmers in dry prone areas as farmers are already storing their harvest in soil pits, and ash is used as desiccating agent and reduce the incidences of rotting and sprouting (Hall and Devereau 2000). In these system, storage can go from 2 to 5 months depending on variety. ...
Vines are the major source of planting material in sweetpotato. Extended dry spells hinder conservation of vines and in turn affect the availability of planting material at the onset of rains in southern Africa. In some cases, improved sweetpotato germplasm has been lost by smallholder farmers in Mozambique due to prolonged dry spells. Small to medium roots provide an opportunity to conserve germplasm and get planting material at the beginning of the rainy season. The objectives of the study were to (i) measure sprouting ability of diverse germplasm of sweetpotato - farmer varieties, improved clones and released varieties and (ii) estimate their ability to provide planting material for the next crop in southern Mozambique. Trials with 29 genotypes were established in a randomized complete block design with two replications at Umbeluzi Research Station and Nwalate Farm in 2015, 2016 and 2017. At harvest, 14 small to medium roots were selected and stored in small plastic dishes filled with dry sand at Nwalate Farm. After four months in storage, 10 similar roots were taken and planted in 1 m row plots arranged in a randomized complete block design with two replications. The trials were irrigated to initiate sprouting and support plant growth during the first four weeks. Data collected were analysed using SAS 1996. All the tested genotypes sprouted after sowing. The number of sprouts per root were significantly affected by the genotype, location and genotype x location x year interactions. Caelan had the most sprouts per root. Sprout length measured at six weeks after sprouting was also significantly affected by genotype, location, year and genotype x location x year interactions. Caelan had vines each long enough to provide 10 cuttings of 10 cm length for rapid multiplication. The number of cuttings depended on the growth habit of the variety. Irene, a popular variety in Mozambique, is erect and bushy and could only provide four cuttings over the same period. Growth habit especially under a changing climate should be considered in breeding programs as an option of facilitating a sustainable and easy seed system.
... Curing induces skin toughness and wound healing process by suberization and lignification of underlying cell layers and development of wound periderm (van Oirschot et al., 2003). However, curing as a post-harvest practice is not common in sub-Saharan Africa; due to cost and security reasons sweetpotato roots are sold as quickly as possible (Hall and Devereau, 2000;Tomlins et al., 2002Tomlins et al., , 2007. Preharvest curing (PHC), sometimes known as in-ground curing or defoliation, is a potential alternative to post-harvest curing in tropical regions. ...
Excoriation (skinning injury) is a serious post-harvest problem for
sweetpotato roots. In industrialized countries, sweetpotatoes are
exposed to post-harvest curing to facilitate skin toughening and
wound healing. However, in developing regions, such a practice is
barely undertaken. Pre-harvest curing (PHC), where sweetpotatoes
are subjected to defoliation before harvest, is a potential
alternative to post-harvest curing. A field trial was conducted in
southern Ethiopia. Roots underwent PHC treatment for 3, 7, 10,
and 14 days, with 0 days as a control sample. Skin adhesion and
chemical composition (ash, crude fibre, crude protein, dry
matter, and starch) of the parenchyma and the periderm were
measured. Storage testing at ambient conditions for 30 days was
conducted.
Skin adhesion among all the treatments was significantly
increased. The maximum skin adhesion was observed after 14
days (358.92 mN.m); however after 7 days of PHC, no significant
change occurred. Root dry matter and ash content remained
unaffected by the treatments. An increase in periderm crude fibre
was observed for treatment samples, indicating lignification.
Parenchyma crude protein concentration demonstrated a sudden
drop in value from the control to 3 days of PHC (5.19 to 2.32%).
For successive durations, crude protein started to increase from
3 days, demonstrating an active protein metabolism. Starch, the
most important constituent affecting palatability and processing
of sweetpotato, was not affected by PHC. Roots subjected to
PHC for 10 and 14 days presented a potential for enhancing
shelf life by having a significantly lower weight loss after 30 days
of storage
This paper recasts the debate over biotechnology by moving past overly general hyperbole, and instead empirically evaluating current experiences with genetically modified crops in Africa. The debate is moved from hypothetical risks, to actual results. The ‘appropriateness’ of GM cotton, sweet potatoes, and maize is evaluated using six criteria widely accepted in crop breeding: demand led, site specific, poverty focused, cost effective, and institutionally and environmentally sustainable. Virus-resistant sweet potatoes are not demand driven, site specific, poverty focused, cost effective, or institutionally sustainable. The environmental sustainability of modified sweet potatoes is ambiguous, but not great. Bt cotton scores low on criteria of demand drive, site specificity, and institutional sustainability. It has ambiguous poverty focus and cost effectiveness. Environmental sustainability is currently moderate, but could potentially be moderate to strong. For Bt maize, the analysis shows low demand drive, cost-effectiveness, and institutional sustainability. It is too early too detect unambiguous site specificity or poverty focus. Environmental sustainability is currently low to moderate, but could potentially be raised. I conclude by examining potential reasons for considerable attention to these three crops despite their generally inappropriate nature for poverty alleviation in sub-Saharan Africa.
This study explored the factors influencing the adoption of tissue cultured sweet potato varieties and impact on productivity among smallholder farmers in Hwedza District of Zimbabwe. A multi stage sampling approach was used to select 133 households for inclusion in the survey. Structured and semi-structured interviews were used to collect data from key informants such as extension officials and biotechnology technocrats located at various institutes in the country. Sweet potato yields were 1.8 tonnes and 0.5 tonnes per ha for tissue cultured and unimproved sweet potatoes, respectively. Adoption was influenced by gender, training, the household's perception of sweet potato enterprise, and age of the household head (P<0.05). There is need to provide training in the production and marketing of the crop and mainly target women farmers in scaling up use of tissue-cultured sweet potatoes given the role they play in household food security achievement.
La patate douce (Ipomoea batatas Lam.) est une culture de subsistance par excellence en Afrique. Comme aliment de soudure, elle joue un rôle majeur dans plusieurs ménages tant urbains que ruraux et sa consommation par habitant est d’environ 84 kg/an. A cet effet, la valorisation de cette culture représente une des meilleures alternatives pour assurer la sécurité alimentaire d’une population en constante croissance et également face à la baisse de la production des cultures vivrières comme le mil, sorgho ou le blé. Pour atteindre cet objectif, une meilleure connaissance de la diversité génétique et la maîtrise des problèmes phytosanitaires s’avère plus que primordiales. Pour cela, des enquêtes ont été menées auprès des producteurs des principales zones de culture en vue d’inventorier les variétés couramment utilisées et les connaissances locales en matière de stockage et de maîtrise des problèmes phytosanitaires de cette plante. Les résultats obtenus ont permis de montrer qu’une diversité de variétés de patate douce est cultivée au Niger. Cependant, le nombre de variétés locales utilisées dépend de la zone d’étude. C’est ainsi que dans la zone d’Ayorou, huit (8) variétés de patate douce ont été recensées contre douze (12) à Balleyara et seize (16) dans la zone de Bengou. Pour lutter contre les ennemis de la culture, les producteurs pratiquent la méthode chimique avec une utilisation abusive de pesticides chimiques qui représentent un danger pour l’environnement. Plusieurs méthodes locales de stockage sont aussi utilisées pour la conservation des tubercules de patate douce (Stockage à l’ombre des arbres, la conservation sur pied, conservation dans de grenier) mais avec des résultats non satisfaisants car les pertes liées au stockage des tubercules restent très élevées.© 2015 International Formulae Group. All rights reserved.Mots clés: patate douce, diversité génétique, connaissances locales, méthodes de lutte, méthodes de stockage, Niger
Sweet potato production in Africa accounts for 11% of global production. It is becoming increasingly recognised as an important crop is Africa, particularly with higher global prices of wheat and other food crops and also its importance in food security. However, the post-harvest aspects, particularly processing and marketing are still very much under developed. The new biofortified orange-fleshed varieties, that contain provitamin A, have great potential to contribute to improved health, particularly in the rural communities. The main challenges for the crop in Africa with respect to post-harvest issues include firstly the reduction in storage pests, particularly weevils because damage can reduce the market value and shelf-life, secondly increasing yields and thirdly improving the marketing systems along the value chain. Improving the consumer perception of sweet potato is important because it is still widely considered to be a 'poor persons' crop. This is particularly vital now that biofortified orange fleshed sweet potato containing pro-vitamin A is increasingly more widely available and can contribute to improved health. This chapter refers to work undertaken to reduce storage pests, reducing losses during transport and marketing and consumer studies to explore marketing issues.
Traditionally, in Uganda most farmers growing sweetpotato practise in-ground storage combined with piecemeal harvesting. Several times during the growing period, between 3 and 7–12 months after planting, large roots are removed from individual plants and small roots are allowed to remain in the ground to enlarge further. The overall aim of the practice is to maintain a supply of roots in the ground for the longest possible period. In a series of four trials, once-over harvests at different intervals after planting and a simulated piecemeal harvesting treatment are compared for yield and quality losses caused by sweetpotato weevils (Cylas puncticollis and C. brunneus). For the once-over harvests, the percentage of damaged roots increased linearly the longer the harvest was delayed. Losses ranged between 3% at a harvest 3.5 months after planting (MAP) and 73% at 9.5 MAP. The total yield and undamaged yield for the piecemeal harvesting treatments were comparable to the yields at the optimum harvest times for once-over harvesting at 6–7.5 MAP. The results indicate that piecemeal harvesting is a practice with a controlling effect on sweetpotato weevil infestation.