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Project Record

Objectives:

Development and validation of strategies that are capable of increasing the value of sweet potato for poor rural farmers. This in turn will contribute to food security.

Background:

An appropriate form of on-farm fresh-root storage will be used, to enable farmers to market their produce at times outside the main harvest period, and so gain higher returns from their crops. In warmer areas of the country, storage is uncommon, and when practised, it is only short term (ca 1 month). Researchers at ARTI Ukiriguru have indicated that farmers are keen to store, but lack knowledge on the relative merits of storage technology. Flexible systems are required, that enable farmers to market their crops either when they need income, or when market prices are most favourable. Data from project R6508 indicates the potential for delayed market entry of the products. Although the primary intervention is on-farm storage, this needs to be seen within the wider context of improvements to handling and crop management having impacts on quality and thus increasing value.

Intended Outputs:

Systems developed that will increase the incomes of poor farmers and other participants in marketing of fresh sweet potato.

Systems for improved storage or handling validated, and benefits quantified, on a case study basis.

Appropriate dissemination literature prepared and disseminated to identified target institutions and through uptake pathways.

Progress and Impact:

Systems developed that will increase the incomes of poor farmers and other participants in marketing of fresh sweet potato.
Baseline studies in identified areas indicated that farmers would welcome the opportunity of increasing their options regarding the management of their sweet potato crop, both for food security and income generation purposes. Initial perceptions were limited to ,in-ground, storage, ie: delaying the harvest of the roots pending household consumption immediate requirements, but this is greatly constrained by sweet potato weevil. Variations in market price according to season indicated off season marketing would be profitable. Market traders welcomed a more evenly spread availability of sweet potato throughout the year.

On-station testing (carried out in two seasons) showed that roots could be successfully stored for up to 12 weeks in unlined and minimally ventilated pit or clamp stores. The stored roots had an acceptable taste with sufficient flouriness. The most important criterion for success was the requirement for selecting roots of high quality for storage.

Systems for improved storage or handling validated, and benefits quantified, on a case study basis.
On-farm long-term sweet potato storage studies were also carried out over two seasons in either pit or clamp stores. In the first season, in two districts (Sengerema and Ukerewe) in the Lake Zone average weight loss of roots was 22% after 16 weeks of storage. Store type did not affect the quality of roots after storage or the proportion of marketable roots. Root quality and the proportion of marketable roots was mostly improved by location where the roots were stored (Sengerema or Ukerewe) and by positioning the stores in the shade under trees and avoiding flooding of the stores from rainwater. The effect of shading was also demonstrated in a separate trial carried out at Dar es Salaam. These were factors not picked up in the on-station studies. Sensory properties of cooked sweet potato were not affected by district, store design, shading or rainwater damage. Based on farm gate prices estimated by the farmers, at Ukerewe 50% of the stores would make a profit of between 15% and 237%. At Sengerema, 60% of stores would have made a profit of between 6% and 200%. These results, however, do not necessarily take into account the fact that sweet potato left in-ground would lose virtually all value because of weevil attack. Market traders discounted the stored roots by between 9% and 45% per sack compared to fresh roots. The main reason was that the roots were lighter. On a price per kg basis, however, the stored roots and fresh roots were very similar. It is thought the discount per sack was because sacks are sold on volume basis, not weight. The store designs offered opportunities and constraints for the farmers. The pit was more difficult to construct but offered more security from animals while the clamp, although requiring more material to construct the root, was easier to build.

Modifications to the positioning of the stores (avoidance of direct sun) in the 2002/2003 trials allowed for more reliable storage. Additional observations from on-farm trials in the coast region indicated that: (a) storage of roots in pits in calcareous soils minimised sprouting; (b) pruning the canopy of sweet potatoes 14 days before harvesting (a handling innovation from R6508) had a small increase on the recovery of marketable roots (from 36% to 47%), particularly if the stores were located in the shade, whereas in on-farm studies in the Lake Zone, pruning increased the recovery of marketable roots from 30% to 49%. Farmers reported that pruning meant that the leaves could be used to feed livestock and it made harvesting easier and roots had less damage. A minority of farmers reported that pruning increased the amount of labour required.

The main conclusion is that this work has significantly increased knowledge about

Project Conclusions:

Systems developed on station and modified on farm that will potentially increase the incomes of poor farmers and other participants in marketing of fresh sweet potato. On farm studies have been undertaken to validate the innovations and benefits have been quantified on a case study basis. A number of dissemination outputs have been produced - including a workshop for key stakeholders in April 2002 and a dissemination leaflet. Further scientific publications will be submitted from the work, but these have not yet been completed. The project goal was that "Poor people benefit from new knowledge applied to food commodity systems in forest-agriculture interface areas.". This project has developed technologies, in partnership between scientists, traders, farmers and extension officers, which when applied will contribute to livelihoods of poor people who depend upon sweet potato for food security and income.

Publications:

WESTBY, A. (2001) DFID/NRI post-harvest activities and links to SARRNET. Presentation to the Southern Africa Root Crops Research Network (SARRNET) Steering Committee Meeting, 15 May 2001.



TOMLINS, K.I., VAN OIRSCHOT, Q., NDUNGURU, G. T., NGENDELLO, T., RWIZA, E. and WESTBY, A. (2001) Report on on-farm experimental trials on long-term sweet potato storage (Gezaulole, Kigamboni). Project Technical Report. Natural Resources Institute (NRI), Chatham, UK. 12 pp.



TOMLINS, K. I., VAN OIRSCHOT, Q., NDUNGURU, G. T., KIMENYA, F., NGENDELLO, T., RWIZA, E. and WESTBY, A. (2002) Long term storage of sweet potato in Tanzania - on-farm
study. Project Technical Report. Natural Resources Institute (NRI), Chatham, UK. 16 pp.



VAN OIRSCHOT, Q.E.A., TOMLINS, K.I., NGENDELLO, T., AMOUR, R., RWIZA, E., REES, D., JEFFRIES, D., BURNETT, D. and WESTBY, A. (2002) On Station Sweetpotato Storage Trials 2000; Testing: Cultivar, Lining, Store type, Ventilation and Damage. Natural Resources Institute (NRI), Chatham, UK and LZARDI, Ukiriguru. 70 pp.



GAZI, H., JORAM, F., PLACID, J., NGENDELLO, T. and VAN OIRSCHOT, Q. (in press) Cassava and Sweetpotato after Harvesting. In: Proceedings of a Workshop held at the Lake Zone Agricultural Research and Development Institute, Ukiriguru, Mwanza Tanzania, 29 April 2002. 105 pp.



KAPINGA, R.E., REES, D., WESTBY, A., NDUNGURU, G.T., RWIZA, E., TOMLINS, K.I., STATHERS, T, JEREMIAH, S. and MBILINYI, L. (2002) Increasing the contribution of sweetpotato to sustainable rural livelihoods in Tanzania. P. 285-291. In: Proceedings of the Twelfth Symposium of The International Society for Tropical Root Crops: Potential of Root Crops for Food and Industrial Resources,Tsukuba, Japan 10-16 September 2000 Nakatani, M. and Komaki, K. (Eds.)



KULEMBEKA, H. P. (in press) Introducing orange-fleshed sweet potato varieties in the Lake zone of Tanzania. In: Cassava and Sweetpotato after Harvesting. Proceedings of a Workshop held at the Lake Zone Agricultural Research and Development Institute, Ukiriguru, Mwanza Tanzania, 29 April 2002. Ngazi, H., Joram, F., Placid, J., Ngendello, T. and Van Oirschot, Q. (Eds.)



NDUNGURU, G.T. (In Press) Handling of sweetpotato during marketing. In: Cassava and Sweetpotato after Harvesting. Proceedings of a Workshop held at the Lake Zone Agricultural Research and Development Institute, Ukiriguru, Mwanza Tanzania, 29 April 2002. Ngazi, H., Joram F., Placid J., Ngendello, T. and Van Oirschot, Q. (Eds.)



NGENDELLO, T. (in press) Potential for long term storage of fresh sweet potato. In: Cassava and Sweetpotato after Harvesting. Proceedings of a Workshop held at the Lake Zone Agricultural Research and Development Institute, Ukiriguru, Mwanza Tanzania, 29 April 2002. Ngazi, H., Joram F., Placid J., Ngendello, T. and Van Oirschot, Q. (Eds.)



RWIZA, E. (in press) Sweetpotato damage and implications for shelf-life. In: Cassava and Sweetpotato after Harvesting. Proceedings of a Workshop held at the Lake Zone Agricultural Research and Development Institute, Ukiriguru, Mwanza Tanzania, 29 April 2002. Ngazi, H., Joram F., Placid J., Ngendello, T. and Van Oirschot, Q. (Eds.)



TOMLINS, K., NDUNGURU, G.T., RWIZA, E. and WESTBY, A. (2002) Improved handling of sweetpotato in Tanzania, East Africa p. 149. In: Proceedings of the Twelfth Symposium of The International Society for Tropical Root Crops: Potential of Root Crops for Food and Industrial Resources. Nakatani, M. and Komaki, K. (Eds.)



TOMLINS, K.I., NDUNGURU, G.T., RWIZA, E. and WESTBY, A. (2002) Influence of pre-harvest pruning and mechanical injury on the quality and shelf life of sweet potato (Ipomoea batata (L.) Lam) in East Africa. Journal of Horticultural Science and Biotechnology 77, 399-403.



VAN OIRSHOT, Q.E.A., NGENDELLO, T., AMOUR, R., RWIZA, E., REES, D., TOMLINS, K.I., JEFFRIES, D., BURNETT, D. and WESTBY, A. (2002) Preliminary observations on the potential for long-term storage of fresh sweetpotatoes under tropical conditions. p. 341-344. In: Proceedings of the Twelfth Symposium of The International Society for Tropical Root Crops: Potential of Root Crops for Food and Industrial Resources. Nakatani, M. and Komaki, K. (Eds.)



TOMLINS, K.I, NDUNGURU, G. T, KIMENYA, F. L and WESTBY, A. (2002) Preliminary report on on-farm experimental trials on long-term sweet potato storage (Gezaulole, Kigamboni) in the 2002/2003 season. Technical Report, Tanzania Food and Nutrition Centre, Tanzania. 7pp.



WESTBY, A., VAN OIRSCHOT, Q., TOMLINS, K., NDUNGURU, G., NGENDELLO, T., KAPINGA, R.,SANNI, L. and OYEWOLE, O. (2003) Root and tuber crop post-harvest systems: lessons learned and future Interventions to contribute to food security and poverty alleviation. Invited thematic paper presented at the 13th triennial Symposium of the International Society for Tropical Root Crops, 8-15 November 2003, Arusha, Tanzania. http://www.istrcsymp-tz.org/ISTRC%20Presentation4.pdf

Associated References:

R6508