Irrigation and Soil-Conservation in African Agricultural History

The archaeological study of African agricultural history has concentrated more on origins and the identification of crop remains than on farming techniques and ancient fields. The latter rarely survive, and even then may be of indeterminate age and apparently atypical, such as hillside terracing or irrigation systems. The subject has been further bedevilled by these unusual instances of preserved fields being regarded as relics of ‘intensive’ cultivation by ‘vanished civilizations’. However, a clearer understanding of African agriculture, through ethnographic and ecological approaches, reveals not only its basically extensive character but also the infinite variety of local specializations (or cultural–environmental adaptations, combining ancient African domesticates and introduced crops which have been ‘Africanized’). This provides a perspective for examining peculiarities of the present and past and claimed instances of ‘intensification’. Conversely the concept of specialization allows us to use, with caution, the preserved remains of old field systems to illustrate more typical ones. Many of the archaeological survivals were not so much ‘intensive’ as ‘over-specialized’, often in isolated and circumscribed situations, notably remote hills in both western and eastern Africa. A moderate example is Inyanga in eastern Zimbabwe with its extensive terraced hillsides of the later Iron Age. Here most of the terraces were not irrigated, but there are hints of complex seasonal arrangements and field techniques. A more extreme, even ‘ultra-specialized’ agricultural system, also of the later Iron Age, which was abandoned in the seventeenth or eighteenth century, is that of Engaruka in the northern Tanzanian rift. This was an essentially isolated and self-sufficient settlement in dry country, absolutely dependent on its exquisite irrigation devices. Eventually this community expired, as its soil was exhausted and its water supplies declined.Finally, there are instances in nineteenth-century East Africa, and from earlier in West Africa, of more open cultural–economic systems producing a surplus for caravans, markets and towns. Technologically these have been no more accomplished or ‘intensive’ than the specializations discussed, but developmentally their achievement has been more effective.