Table 2: Arable land resources of tropical Africa assuming no further deforestation (calculated from FAO, 1986).
Per Capita arable land+
Total arable land in 1990
Assuming no additional land is brought under cultivation, and
that population continues to increase at 3.2% yr-1.
Table 3: Population carrying capacity of Africa for different scenarios (FAO, 1984).
Actual population in 1975 was 380 million.
Carrying capacity at different input levels
Ratio to population of 1975*
Despite the high potential and vast resources, it is ironic that the extent of soil and water degradation in Africa is equally alarming. Natural resources are severely degraded because of mismanagement, exploitation for short-term gains and widespread practice of low input subsistence farming (Lal, 1988, 1990). Resource-based continuous cropping, even at low levels of productivity can lead to an average nutrient loss of 10 kg N, 1.8 kg P and 7.1 kg K ha-1 yr-1. The rate of nutrient loss is about twice as much in Eastern Africa, and is likely to increase because of the increase in demographic pressure and intense cropping.
Despite common belief, Africa has an impressive history of high-quality research data. Some of this
research in soil and water management and improvement was summarised by Lal (1992).
2.2 The Conservation Tillage System:
The conservation tillage system can be viewed as composed of natural factors, which influence the
various human and other capacities to manage soil. In this respect, soil is viewed as a small part of a larger system, made up of natural and management factors. Management factors are strongly influenced by various capacities, which in turn are dependent on the natural factors. Of essence, soil has to accommodate all and various needs imposed on it by both nature and humans.
For example, a soil in say, southern Sudan has certain natural qualities which will determine its conservation input level and needs. The manager may have strengths or weaknesses in capacity to manage soil and may for example need animal traction input and conservation tillage implements which may or may not be available. The same farmer may have the animals and equipment but have shortcomings in design, training, maintenance and other capacities. These capacities may be limited due to natural, technological or socio- economic factors. This vicious cycle may explain why conservation tillage is such a complex and multi-sectoral involvement.
This paper is published in: Kaumbutho P G and Simalenga T E (eds), 1999. Conservation tillage with animal traction. A resource book of the
Animal Traction Network for Eastern and Southern Africa (ATNESA). Harare. Zimbabwe. 173p. A publication supported by French Cooperation, Namibia. For details of ATNESA and its resource publications, see http://www.atnesa.org