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Market Oriented Yam Storage

Root and Tuber Development Guides (2)

Reducing Losses and Increasing Income

Published by:

Deutsche Gesellschaft fr Technische Zusammenarbeit (GTZ) GmbH

Project: "Integrated control of the larger grain borer - small
farmers post-harvest systems"

Albert Bell, Section 4541
P.O. Box 5180
D-65726 Eschborn, Germany


The "Sedentary farming systems" Project, Sunyani, Ghana

Dr. Christian Henckes

P.O. Box 9698, K.I.A.

Accra, Ghana


with input from: Otto Mck, post-harvest consultant
D-22885 Barsbttel, Germany
Cover photo: Dr. C. Henckes, GTZ
Photo Yam Storage: Dr. B. Schuler, DSE / ZEL
D-82336 Feldafing, Germany
Layout: Gerlinde Quiter, GTZ, Section 4541
e-mail :




1. Traditional and Market Oriented Yam Storage

2. Improved Yam Storage

3. Advantages of the Improved Yam Storage System

4. Special Hints

5. Yam Tubers in the Kitchen

6. Further Information


Root and Tuber Development Guides (2) - their Objective

Post-production operations include all steps and actors from production to consumption. Therefore, a systems approach should be adopted when analysing constraints and introducing improvements. A methodology to analyse post-production systems has been developed by the Food and Agriculture Organisation (FAO) of the United Nations (UN) and the Deutsche Gesellschaft fr Technische Zusammenarbeit (GTZ) GmbH, with the support of the Centre de Coopration Internationale en Recherche Agronomique pour le Dveloppement (CIRAD) and the Group for Assistance on Systems relating to Grain After-harvest (GASGA). Experience with this systems approach in the field of roots and tubers (R&T) has shown a great potential for improving the processing and marketing of this crop and thus generating extra income, especially for women in Africa. Therefore this system approach is being promoted through this leaflet.

R&T commodities are important staple foods and cash crops for the rural population of sub-Saharan countries of Africa. This development guide is a practice-oriented extension leaflet showing how rural families can make best use of R&T . It is part of a series, which intends to help conserve and add value to R&T. Each issue is based on practical experience acquired in the post-harvest research and development work conducted by many partners, especially in West Africa. Partners include the International Institute of Tropical Agriculture (IITA), national research institutes and universities and projects supported by the GTZ in countries such as Benin, Ghana, Kenya, Tanzania and Togo.

Each leaflet highlights a particularly promising approach in R&T post-production technology, including operations such as storage, marketing or processing. The innovations presented in this series may help overcome traditional drawbacks, such as the high perishing factor , the tedious nature of the work or the lack of profitability. The economic viability of the proposals made in these leaflets has to be carefully assessed with regard to the specific circumstances. As the framework conditions differ widely, general recommendations on the profitability of an innovation cannot be made here. The extension workers involved in the promotion of R&T must be aware that the technical aspects of innovations are fairly simple to manage in most cases. However, much attention must be paid to their socio-economic implications.

Guides on "Cassava Flour Production" and "Processing of Yams" are in preparation while one on "Cassava Chipping Machines" is already available.

The post-production activities of partner organisations and the GTZ in the area of R&T are part of the effort of the German Federal Ministry for Economic Cooperation and Development (BMZ) to support the implementation of stipulations made in Agenda 21 .on the following topics among others:

food security,

poverty alleviation,

promotion of women,

strengthening the role of rural families and

promotion of sustainable agriculture.

Improved Yam Storage

- Raised hut made of local material -

1. Traditional and Market Oriented Yam Storage


Yams belong to the most important food crops in the West African countries of Nigeria, Cte d’Ivoire, Ghana, Togo, Benin and the Republic of Guinea . Their production account s for about 95% of the world production. Yams are grown in the northern forest and southern savannah zones but are consumed in all parts of these countries. Yams, particularly white yams, are considered a prestigious food and are preferred to other foods by the urban populations. Most yams are marketed as fresh tubers and prepared for consumption within their country of production. Transportation and marketing is carried out by the private sector.

Losses in Traditional Yam Storage

Yams are seasonal crops. The tubers of white yams can be stored for several months under adequate storage conditions and under regular surveillance. However, there are considerable losses using traditional yam storage structures due to bacterial and fungal rotting, rodent attack, sprouting and other factors including theft. As a consequence, over one million tons of tubers may be lost per annum during storage in West Africa.

Yam tubers are very delicate and easily bruised during harvest and handling. They spoil quickly due to physiological decay and rotting. High temperature may cause considerable physiological losses even to undamaged tubers. Rodents and other pests including insects attack the tubers, which are even more susceptible to rotting once they have been injured by pest organisms. Sprouting occurs easily and decreases the quality of the tubers indicating that sprouts should be removed. The amount of loss depends, in the first place, on storage system, yam variety and length of storage.

Traditional yam storage structures such as pits, trench silos and heaps in the field are very difficult to manage. These structures cannot protect the yam tubers sufficiently from losses described above. Continuous inspection of tubers is very difficult and in a lot of cases impossible in most of the traditional storage structures so that losses are only detected when the yams are removed from the store for use or for sale. In many cases, the farmer cannot quickly sell when market prices are high because of the poor access to the store as a consequence of poor road conditions, especially during the rain seasons.

Objectives: Reducing Losses and Increasing Income

The prices for white yams increase considerably before the new harvest, as the supply with tubers of a reasonable quality diminishes. The reasons for this phenomenon are inadequate storage practices and a poor marketing system. It is very profitable for farmers to practice a market oriented store management and raise their incomes by providing well preserved white yams as long as possible. This leaflet shows how farmers can achieve this goal.

The choice of an appropriate storage site, either situated in the village or close to the road or market, is a precondition for the improvement of the storage system, but also for regular inspections of the tubers, easy marketing and higher income. Using preventive measures, constructing suitable yam stores (raised huts or other structures that have been successfully tested) and practising regular surveillance of the stored tubers are recommended measures of quality maintenance.

Target Groups

This leaflet addresses agricultural extension workers, NGOs and others who assist small-scale farmers. Furthermore, this leaflet is directed at policy and decision makers in the field of agriculture to sensitise them to the adequate frame of conditions and economic potential of a good R&T storage management and marketing .

2. Improved Yam Storage

.Farmers wishing to improve their income all year round must be aware of customer demands, especially those living in urban areas. Good quality and varieties of yam tubers preferred by consumers and possessing good storage qualities should be chosen . The best varieties between regions should be chosen and the advice of the local extension services should be sought on this topic. The following steps are recommended :

Pre-harvest measures

Use only healthy planting material (tubers or minisets) derived from tubers of medium size and regular shape. Grow yams exclusively on fertile soil that is not contaminated by nematodes, termites or other infestations that may harm the crop.

Careful harvesting, handling and transportation

Care should be taken that tubers are harvested without squeezing or breaking them. Use appropriate tools for lifting the tubers. Avoid exposure of the yams to strong sunlight for longer period s . Handle tubers gently and never drop them. The best way to transport yams is by placing them into baskets or other containers of appropriate size.

Hygienic Measures

Choose only healthy and undamaged tubers for storage. They should be of medium size and regular shape. Grade tubers according to their size before storing them so that a uniform quality can be provided at any time. Tubers that are not suitable for storage or will not fetch a good price should be separated from the market tubers before storing. They may be used for home consumption. Clean the storage structure thoroughly before storing and keep it clean at all times. Keep the surroundings clean and clear to discourage rodents.

Construction of the Raised Hut

.If possible, t he raised hut should be constructed in the village , near the market or close to the road for easy access by truck (see photo page two).

The raised hut is a storage structure made of locally available materials such as wood, bamboo, straw, etc. Its dimensions may vary according to need . The hut should be at least one meter above the ground. Rat guards should be fixed to the legs to prevent access by rats and mice. The rodent guards consist of metal sheets that are wrapped around all legs and have a length of at least 30cm. Fix the rodent guards with some nails. The store should be protected against theft with a strong padlock. .In some areas, protective measures against termites have to be considered. A simple and cheap method for example is dipping the lower part of the legs that support the hut into wood preventatives or neem oil.

Inside the raised hut, the yam tubers are best stored on shelves so that they can be inspected easily and rotten tubers should be removed. Large tubers are placed in one, whereas small tubers in two to three layers. Different yam varieties should always be stored separately.

Regular Surveillance

The tubers should be inspected at least every three weeks. Remove rotten tubers immediately to prevent further contamination. Partially damaged tubers may be chipped and dried or used immediately. Remove sprouts before they have attained a length of 50cm. During long storage, yam tubers loose moisture and shrivel. This minor quality change, however, is unavoidable and accepted by consumers as long as fresh tubers are not available on the market. In dry climates the shrivelling can be reduced by covering the tubers with yam vines, straw or similar material of plant origin.

3. Advantages of the Improved Yam Storage System

Only tubers in good condition should be chosen for storing. Amongst all possible storage constructions the raised hut is the most suitable for the following reasons :

- it can be cheaply constructed using locally available materials ,

- it provides excellent natural aeration .,

- it’s construction prevents access by rodents ,

- it can be locked against thieves .,

- it facilitates regular checks .,

- it can also be used for storing maize, beans and other commodities.

.In addition, a suitable location of the store reduces the need for handling and permits easier and year round transport (even smaller quantities) to the market. It reduces risks from bushfires and access by farm animals. Regular inspection facilitates sales decisions and improves the farmers position with respect to traders . The improved yam storage system has the following advantages :

1. Fewer tubers will be lost during storage.

2. .The number of good quality yams will increase.

3. The period of storage can be prolonged.

4. The tubers can be sold at times when the prices are high.

5. Less tubers will be lost as a result of reduced handling.

The ultimate result will be a substantial increase in income, as good yam tubers fetch high er prices, especially towards the end of the storage period. A case study in Ghana has shown that the gross margin of yam farmers may increase by over 50% if farmers apply the market oriented yam storage system described .

4. Special Hints

... Related to the Extension Work

The most effective way of introducing innovations is by employing the principles of participation. Past experience has shown that the first step is to analyse the local situation together with the farmers and design solutions for their problems with them. This empowerment will make it more likely to attract their interest and implement some of the recommendations. The extension agent obtains the role of the facilitator.

To ensure sustainability, support should not be limited to technical and financial assistance, but should include the management skills required to run the business profitably. Extension agents must support the farmers’ decision making procedures by transmitting the necessary quality assessments procedures and advising the farmers in choosing the right time for marketing. This includes regular information on the fluctuations of the market (supply and demand and resulting prices).

... related to the Farmers

Self-help initiatives are a key factor for introducing innovations successfully . Groups are stronger than individuals and it is recommended to initiate farmers groups which assist each other in terms of information exchange, transport and the construction of storage huts . Changes initiated by the target group are bound to be more sustainable than changes proposed from external sources because of a stronger feeling of ownership.

... related to Policy Issues

The success of the market oriented yam storage using improved methods depends, to a large degree, on the economic framework conditions. The introduction of appropriate food quality standards will create a positive environment for this innovation. Features like shrivelling, physiological and microbiological deterioration, traces of rodent or insect attack, and any changes in appearance, smell or taste should be considered in such standards. Today, too many consumers accept the low quality of tubers towards the end of the yam season because of a lack of choice and standards. This attitude may engender nutritional and health hazards.

5. Yam Tubers in the Kitchen

The following dish will be highly appreciated by your whole family, especially if it is prepared with yam tubers that have been conserved under perfect conditions as described in this leaflet. The recipe has been kindly provided by Petra Henckes from Sunyani, Ghana:

Yam Balls


White yam 1 tuber

Eggs 3 - 4

Onion 1

Pepper to your taste

Salt to your taste

Nutmeg to your taste

butter/ margarine 2 tablespoons


1 Boil yam.

2 Mash it.

3 Mix butter and egg yolks with it.

4 Form yam balls (orange size).

5 Deep fry the balls (oil must be very hot).

Serve yam balls with any sauce.

6. Further Information

For further information, please contact your national agricultural service, research institutes and universities in your country. Often, local non-governmental organisations (NGOs) can also provide relevant information, for example the offices of Sasakawa-Global 2000.

Sasakawa-Global 2000 - Africa
SG 2000

BP 04-1091 Cadjehoun

Cotonou / Benin

Tel. 229-30 04 59

Fax 229-30 06 37


SG 2000

PMB Airport

Accra / Ghana

Tel. 233-21-77 47 50

Fax 233-21-77 34 67


SG 2000

PMB 3130

Kano / Nigeria

Tel. 234-64-63 48 90

Fax 234-64-63 81 90


SG 2000


BP 7018

Ouagadougou / Burkina Faso

Tel. 226-31 18 26

Fax 226-31 26 58

SG 2000

Service Naional de la Promotion Rurale et la Vulgarisation

BP 576

Conakry / Guinea

Tel. 224-41 14 78

Fax 224-41 14 78

SG 2000

P.O. Box 495

Dar es Salaam / Tanzania

Tel. 255-51-36 882

Fax 255-51-36 882

SG 2000

c/o Ministry of Agriculture

P.O. Box 12771

Addis Ababa / Ethiopia

Tel. 251-1-51 05 84

Fax 251-1-51 08 91

SG 2000

Ministry of Development and Environment

BP 1093

Bamako / Mali

Tel. 223-22 83 62

Fax 229-22 39 14

SG 2000

BP 7525

Lome / Togo

Tel. 228-22 25 52

Fax 228-22 25 52

SG 2000

c/o Ministry of Agriculture

Agricultural Research and Extension Service

Asmara / Eritrea

Tel. 291-1-11 74 28

Fax 291-1-18 14 15

SG 2000

CP 4247

Maputo / Mozambique

Tel. 258-1-49 00 04

Fax 258-1-49 14 17

SG 2000

c/o Ministry of Agriculture, Animal, Industries, and Fisheries

FSSP Buildung

Entebbe / Uganda

Tel. 256-42-20 621

Fax 256-42-20 676

Literature and advice on practical management regarding post-production systems can also be found on the Internet at:

Financed by:

German Federal Ministry for Economic

Cooperation and Development (BMZ)