An assessment of the success of a geomorphologically based reconnaissance soil survey in eastern Zambia

Abstract

The success of a 1:100,000 scale reconnaissance soil survey of the Mtetezi River area in eastern Zambia is assessed using independent profile data obtained from six grid-based detailed pilot surveys undertaken prior to reconnaissance soil mapping. The quality of the soil map is first determined by measuring the success with which the map and its accompanying legend and report estimate correctly the proportions of different soil classes within mapping units (Estimating Success). Secondly, an evaluation is made of the ability of the map to predict correctly the kind of soil occurring at any point within the mapped area (Survey Success). Estimating Success and Survey Success are calculated on both an “unweighted” and a “weighted” basis, the latter compensating for impurities within mapping units based on measurements of mapping consistency. Estimating Success scores are 73% (unweighted) and 78% (weighted), and Survey Success scores are 38% (unweighted) and 22% (weighted). These compare favourably with scores reported in other known studies. The relatively low Survey Success scores reflect the fact that many of the reconnaissance map units are soil associations. Survey Success is shown to vary across the geomorphic units used as a basis for the reconnaissance soil map. It is suggested that all soil surveys should include an estimate of their success and that the methodology described in this paper provides a simple cost-effective method suitable for this purpose.