Box 1: Soil degradation or declining fertility
“Soil erosion, widespread in all areas of Sub-Saharan Africa, is perhaps most serious in Ethiopia, where topsoil losses of up to 290metric tons a hectare/yr have been reported for steep slopes. In West Africa, losses of 10 to 20 metric tons of soil per hectare/yr have been reported even for very gentle slopes. Wind erosion is significant in drier areas. There are numerous reports of a decline in the fertility of cultivated land in many parts of the region. A common feature of degradation is the removal of weakening of vegetative cover by overgrazing, over-cultivation, or deforestation, which exposes the soil to rain and wind. With several notable exceptions government efforts to combat soil degradation have failed because soil conservation usually requires the farmer to provide extra labour – labour that is often unavailable. Moreover low prices for produce coupled with uncertain land tenure make conservation financially unattractive.” [IBRD (1989)]
“The grave erosion which occurs on ploughland from time to time has often induced an “old- timer” to say ruefully that we should never have put a plough into Africa. However, the relatively unscarred Africa which carried a small population on the basis of shifting cultivation remained curiously unprogressive in a world which was advancing in scientific knowledge by leaps and bounds. Western interference caused the population to increase while accelerating the rate of deterioration of the soil. The biggest problem is not the soil directly but the people on the soil. Soil must be used by good farmers to remain productive. The emphasis must always be on the people who care for the land, not directly on the land. A poverty-ridden people pass their suffering to the soil” (Maher, 1950).
In less obvious ways, agricultural soil degradation and water losses have hardly been associated with tillage, its drudgery and power requirements. Tillage however remains, a great contributor if not the prime cause of soil degradation and erosion. In some ways the absence of special consideration for tillage as a prime issue may be associated with the young agricultural engineering profession in the region.
hard pans and, in doing so build giant natural water "tanks", in which they store enough water for the season. At the same time the smallholder farmers, using the hand hoe or traditional animal drawn mouldboard ploughs find themselves busy expelling the little moisture that has been received to the thirsty sunshine. They do this by the traditional heavy soil manipulation in primary or secondary tillage operations.
Traditional manual tillage or higher level, animal draft technologies have remained void of common-knowledge awareness of the importance of tillage and its practice. Technologically, neither the common hoe, nor the animal drawn mouldboard plough have offered much choice or creativity with regard to tillage. In largescale farming and especially so for wheat farmers, modern tractor based tillage has seen a wider level of choice, knowledge and creativity as these farming systems have borrowed directly from the developments of the Western World. In this regard, tine implements and single pass, minimum or no-till pneumatic seeders and other implements such as the prickle harrow have been introduced.
For example, in Kenya it is common to see a large scale wheat farmer in Timau area with a bumper wheat harvest when all the smallholders around them have a total crop failure especially in seasons when rainfall is scanty. The large farmers are able to use technology to break their
1.2 The concept of sustainability
The concept of sustainable development emanated from the document developed by three international agencies: World Conservation Union, United Nations Environmental Programme (UNEP), and the World Wildlife Fund (WWF) in 1980 (Dieren, 1995). Later in 1983 the World Commission on Environment and Development (WCED) was established by UN General Assembly "to undertake a global enquiry on the prospect of combining social and economic development with environmental protection". It was anticipated that the Commission would work out proposals for long-term environmental strategies which would stimulate a sustainable development in the foreseeable future. The Commission compiled an important document (WCED, 1987) where the concept of sustainable development was formulated as were legal principles for environmental protection and
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