Land degradation processes, such as soil erosion, which threaten the sustainability of agricultural production have been studied for many years. While research progresses on the processes, little advance has been made on translating results into terms which can be used directly in the design of appropriate and economically justified forms of soil conservation and land husbandry. Research by the authors has shown how soil erosion affects the potential of land to produce crops. Simple models have been developed which provide a first approximation of the impact of soil erosion on future production, to be used as a baseline against which the benefits of soil conservation can be compared. The concepts of soil life and residual suitability have been developed as a measure of the sustainability of the production system considered. In this paper a simple experimental technique to derive the future production and the residual suitability of land is proposed. The method is based on the principle of sequential testing and uses a simple graphical technique to translate information on production and erosion into a crop production forecast. The method and its application are illustrated using examples from Botswana and Sierra Leone.