Felix I. Nweke

Cassava processing in sub-Saharan 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 flavours and appearances for different areas and markets. Many different processing techniques are used, some of which make intensive use of fuelwood 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.

Contributions of Men and Women to Food Crop Production Labour in Africa: Information from COSCA

It is widely reported that women provide the bulk of food production labour in Africa. Since efficient targeting of improved technologies demands an understanding of who is likely to use them, and new farm technologies have often been inappropriate for womens needs, this paper presents the relative contributions of men and women to food production labour in six major cassava-producing countries of Africa. The paper is based on farm-level information collected within the framework of the Collaborative Study of Cassava in Africa (COSCA). While the number of fields in which women provided more labour for each farm task increased consistently from the initial farm operations, such as land clearing and seedbed preparation, through sowing (planting) and weeding to the final farm operations such as harvesting and transportation, for which women provided more labour for the largest number of fields, the reverse was the case for men. The relative number of households where females provided more field labour than males was higher among female-headed households than among male-headed ones. Such households were characterized by a lower working age male/female ratio, and/or were engaged in tree crop production, which often absorbed male labour. Villages where females provided more field labour than males were more common in remote areas where access to markets was poor and population density sparse, or in countries where men had fled the villages because of political repression. Such villages were also more common among non-Muslim communities than among predominantly Muslim societies. On the whole, however, men contributed more labour in significantly more fields than women in most places. These observations suggest that it could be misleading to generalize that women are providing the bulk of food production labour across Africa. They provide clear evidence of gender division of labour on the farm, and help to explain gender bias in agricultural extension efforts in Africa. Recommendations that pre-harvest extension activities should be mainly directed at women have hardly been heeded. It is recommended that these activities should be targeted at both men and women, but more towards women where men have fled the villages for political reasons or for commercial ones such as poor market access opportunities.

Future prospects for cassava root yield in Sub-Saharan Africa

Primary data collected over a wide area in Africa show that average cassava root yield is not declining as the population increases because the land is being cultivated more intensively in response to demographic pressures. Although fallow periods are becoming shorter, organic manuring, improved market infrastructures and the use of purchased inputs such as labour compensate for this. The yields of improved cassava varieties in Nigeria show that technology can be relied upon to raise production in future, provided that the conditions necessary for the widespread adoption of Improved varieties prevail in most African countries.

Trends in food crop yields under demographic pressure in sub-Saharan Africa : the case of cassava in southeast Nigeria

Research in 1973 attributed large cassava root yield differences among three villages in southeast Nigeria to equally large population density differences. In 1993, the Nigerian national team of the Collaborative Study of Cassava in Africa (COSCA) went back to the three villages to see whether population growth had led to yield declines. They found that the wide gap in yields between the high and low population density villages was maintained, apparently due to differences in soil type, fallow periods, cassava plant densities and harvest dates. Cassava root yield had doubled in the high population density area, increased but not doubled in the medium population density area and declined in the low population density area. The differences in the yield trends among the three villages were due to the use of improved cassava varieties in the high population density area.

Soil fertility status and cassava yield in Tanzania: (I) nutrient levels in cassava-growing soils

One of the main objectives of the Collaborative Study of Cassava in Africa (COSCA) was to obtain data on the cassava production systems in Sub-Saharan Africa. In Tanzania soils grown to cassava and other major arable crops in 45 villages were sampled in order to assess and compare their fertility status and relate the fertility status to factors which could have given rise to any observed variations. Soils were collected from 0–20 and 20–40 cm depth and 16 physicochemical properties were considered. Both climate and altitude significantly influenced at least 11 of the soil properties in fields grown to cassava. Human population density and cassava mixture significantly influenced particle-size distribution, total nitrogen, organic matter (OM) and exchangeable acidity. The soils of the non-humid and those of the low altitude zones were respectively, on average, more fertile than those of the subhumid and mid-altitude zones. Comparatively, soils grown to cassava were as fertile as or more fertile than soils grown to other arable crops, except in the cases of Mg++, total exchangeable bases (TEB) and effective cation exchange capacity (ECEC) for soils grown to banana or plantain. Based on the rating scale for optimum cassava performance, only nitrogen was found to be lower than the critical minimum required by cassava and thus needs to be applied in most of the soils. On average, the soils of the entire area sampled were generally medium to high in fertility.