Habitudes de consommation et leurs implications pour la recherche et la production en Afrique tropicale

Réunion: Symposium triennal sur les plantes-racines de la Société internationale pour les plantes-racines tropicales - Direction Afrique, 8-12 sept. 1980, Ibadan, NGDans IDL-471

Farm Level Practices Relevant to Cassava Plant Protection

This paper is based on information collected during the Collaborative Study of Cassava in ten countries of Africa and considers the incidence of cassava mealybug (CMB) and green mite (CGM) pests and African cassava mosaic virus (ACMD) and bacterial blight (CBB) diseases of cassava in relation to farm practices. African cassava mosaic disease was the most widespread of the four problems assessed and was observed in almost all the representative villages in West Africa. Cassava mealybug was the least widespread, although the incidence was relatively high in Nigeria, Malawi and Tanzania. Cassava greenmite was most widespread in the countries of eastern and southern Africa, whereas CBB was widespread in Nigeria and Uganda. The problems of CGM, ACMD and CBB were not higher in any other climate zone, than in the humid climate zone, while those problems were not less severe in any other climate zone, than in the humid climate zone, while those problems were not less severe in any other climate zone than in the subhumid climate. While the incidences of the various pests and diseases varied between villages which used and others which did not use purchased inputs were used. In Nigeria where improved varieties were mostly used, the symptom severity scores of all four pest/disease problems were lower for the improved varieties that had been released in the 1970s than for the local land races. Similarly, based on information from the ten countries, the symptom severity scores of the four problems were lower among villages which had easy access to a market than in other villages. The symptom severity score of the four problem were lower when cassava was grown in rotation with other crops than in other situations. The problems were also lower under continous cultivation systems although the reason is not clear. There was a high rate of turnover in the land races grown and susceptibility to pests and diseases was on of the most frequently mentioned reasons for this

Collaborative Study of Cassava in Africa (COSCA); project description: COSCA working paper, No. 1

COSCA was initiated through the realization that the potentials of cassava depends on availability of more detailed and reliable information on the cassava crop. The general objective of COSCA is therefore to improve the relevance and impact of agricultural research on cassava by International Agricultural Research Centres and National Agricultural Research Systems in Africa in order to take full advantage of. the potentials of cassava in increasing food production and incomes of poor people. COSCA will be conducted in Cote d'lvoire, Ghana, Nigeria, Zaire, Uganda and Tanzania. The major consideration in the choice of these countries is that they provide a wide range of conditions of climate, altitude, population density, and market access infrastructure in the important cassava zones of the continent in order to collect relevant information over a wide range of ecologies in the cassava belt of Africa. A systems approach, with a multi-disciplinary team, is adopted in COSCA to study cassava within the context of mixed farming and food systems. Not only will information be collected on production, processing, marketing and consumption of cassava, but also similar information will be collected on other crops which are grown or consumed in the same farming and food systems. COSCA study will be conducted in three phases, Phase I will involve broad characterization of the cassava producing zones. Information will be collected by group interviews at the village level and by key informant interviews at institutional level. Phase 1\ will involve characterization of individual production, processing, marketing and consumption units. The information will be collected on single visits and collection methods will include direct observations, field measurements, and individualized interviews. Phase III is an extension of Phase II but involves more intensive surveys with repeated interview visits for collection of information on seasonal variables. The components of COSCA are integrated into one study for data collection and analyses. Integration is assured at data collection stage through the sampling process. Phase II survey will be conducted on a subsample of Phase I sites and Phase III survey win be conducted on subsamples of Phase II. During the analyses, COSCA study is further integrated since each hypothesis will be tested with information collected at different phases and on different components. The time frame is 4 years between 1988 and, 1992, with intermediate outputs issued at the end of each phase. These outputs will be disseminated through a working paper series, research reports, journal articles, books and conference proceedings, especially the triennial symposia of the African Branch of the International Society of Tropical Root Crops

COSCA project description: COSCA working paper, No. 1

The general objective of the Collaborative Study of Cassava in Africa (COSCA) is, to improve the relevance and impact of agricultural research on cassava by international agricultural research centres (!ARC) and national agricultural research systems (NARS) in Africa in order to take full advantage of the potential of cassava in increasing food production and incomes in Africa. The countries participating are Cote d'lvoire, Ghana, Nigeria, Zaire, Uganda and Tanzania. The major consideration in the choice of these countries is that they represent the important cassava zones of the continent and provide a wide range of ecological and socio-economic conditions. COSCA has adopted a systems approach, with a multi-disciplinary team, in order to collect information on cassava within the context of African farming and food systems. Not only will information be collected on production, processing, marketing and consumption of cassava, but similar information will be collected on other crops which are grown or consumed in the same fanning and food systems. The Collaborative Study of Cassava in Africa will be conducted in three phases: Phase I will involve a broad characterization of the cassava producing zones. Information will be collected by group interviews at the village level and by key informant interviews at the institutional level. Phase II will involve characterization of individual production, processing, marketing and consumption units. The information will be collected on single visits and collection methods will include direct observation, field measurements, and individualized interviews. Phase III is an extension of Phase II, but involves more intensive surveys with repeated interview visits in order to collect information on seasonal variables. These components of COSCA will be integrated into one study for data collection and analysis. Integration is assured at the data collection stage through the sampling process. Phase II of the survey Will be conducted on a subsample of Phase I sites; and Phase III will be conducted on subsamples of Phase II. During the analysis, the study will be further integrated, since each hypothesis will be tested with information collected at different phases and on different components. The three phases have been spread over a 4-year time frame (1988 -1992). After each phase is completed the output will be disseminated through a working paper series, research reports, journal articles, books and conference proceedings, in particular the triennial symposia of the African Branch of the International Society of Tropical Root Crops

Cassava processing in subSaharan Africa: the implications for expanding cassava production

Cassava makes an important contribution to improving food security and rural incomes in sub-Saharan Africa, as it is tolerant of drought and poor soil and its cultivation does not require much labour. However, the fresh roots are bulky and perishable and need to be processed before they can be marketed; processing also removes the cyanogens which make many varieties poisonous in their raw form. Cassava roots are turned into granules, flours, pastes and chips, with a wide range of flavour and appearances for different areas and markets. Many different processing techniques are used, some of which make intensive use of fuel wood while others require a plentiful water supply. These requirements, as well as the need for a good transport and marketing infrastructure, limit the expansion of cassava production in sub-Saharan Africa, but technical solutions are being found

Consumption patterns and their implications for research and production in tropical Africa

Meeting: Root Crops Symposium, 1st, 8-12 Sept. 1980, Ibadan, NGIn IDL-271

Impact of agroecology on soil fertility status and cassava yield in Nigeria: II: contributions of soil properties to cassava yield variations

Cassava yields obtained from farmers' fields in Nigeria during the Collaborative Study of Cassava in Africa (COSCA) survey gave an average root yield of 14.5 t/ha and an average harvest index of about 0.56. The average root yields from both the sub humid and non humid zones were the same but significantly higher than that obtained from the humid zone. The soil properties which showed significant correlation with cassava yield parameters were sand, silt, clay, exchangeable Mn and Na, available P and OM as well as Mg:K and Mn:P ratios and exchangeable sodium percentage (ESP). Seven properties that contributed most to root yield variations were OM, pH, sand, exchangeable Ca, Mg and Mn, as well as ESP. The total variation accounted for by the soil variables was only 10% out of which Mn accounted for the highest proportion of about 3%. The overall contributions to other yield parameters were also low ranging from about 5% in shoot yield variation through about 10% in harvest index to about 12% in stand density. The overall low contribution was attributed to other environmental factors which influence cassava performance thus indicating that factors other than soil properties such as farmers' practices and climatic elements are also important determinants of cassava yield. Furthermore it was also see that nutrient ratios also made important contributions to cassava yield variation

Importance of cassava processing for production in subSaharan Africa

This paper is based on information collected from about 600 villages in the ten largest cassava-producing countries within the framework of the Collaborative Study of Cassava in Africa (COSCA). The objective of the paper is to show that growth in cassava production in the region will depend more on improvement in processing technology than on breeding for low cyanogenic potential. The paper shows that in the region, cassava is produced for sale. Most of the cassava produced is processed to improve quality and reduce marketing costs and hence make cassava competitive with food grains in the market. Farmers therefore select cassava genotypes for postharvest attributes. Whether the cassava variety has high or low cyanogenic potential is not important to such farmers so long as the variety has other derived attributes. There are, however, certain population groups which need varieties with low cyanogenic potential for specific reasons