The influence of agricultural practice on soil erosion process in central Tanzania

Abstract

The problem of accelerated soil erosion in central Tanzania is chronic and there does not seem to be a straight-forward answer. Prospective solutions to the physical problem are made difficult by the fact that land use alternatives are limited by the socio-economic infrastructure. Associated processes of erosion and disposition remain part-and-parcel of an established 'conservative' social system operating on a relatively unflexible natural physical system. The two systems are not in harmony to maintain a desirable equilibrium. This paper outlines firstly the geomorphic setting of Kondoa, a district in central Tanzania threatened by accelerated soil erosion. The physical characteristics of the area are then related to the occurrence of erosion. A brief review of agricultural development during the colonial period is made in relation to measures taken to accommodate the problem and these are contrasted to current erosion control measures. Finally, suggestions for the future are made. The main emphasis is on establishing harmony among ecological systems. Kondoa is a district in Dodoma Region covering an area of about 13,200 sq. km. To the east. Kondoa shares a boundary with Kitete district, Arusha region while to the north it shares a boundary with Hanang district, A[usha region. It is bounded by Singida and Dodoma districts to the west and south, respectively. The district lies within the central rift zone, i.e. the southward extension of central Tanzania's eastern rift and is, therefore, characterized by block faulting topography. The mean altitude of Kondoa Highlands is about 1550 m.a.s.l. (metres above sea level). Kondoa is drained in a greater part by ephemeral rivers and streams and lies within the Bubu river catchment. In addition, there are various internal drainage basins with Lake Haubi in the north-east. Lake Biacha Sese swamp and its basin at the southern tip of Chi vi river being the most conspicuous. The climate is semi-arid with a mean annual rainfall of between 600-800 mm. The climate permits the growth of dry montane forest, open woodlands and bushed grasslands. Most of the natural vegetation has been cleared for cultivation but has also changed as a result of overgrazing. Consequently, extensive gully erosion has developed dramatically; 29.5 per cent of the total district area is eroded (1,256 sq. km. or 125,599 ha).