Abstract
To communicate the results of erosion research more effectively to planners and decision-makers, it is suggested that estimates of the life-span of a soil might have greater meaning and impact than specific rates of soil loss. A simple model is presented based upon estimates of rates of soil loss existing depths of productive soil, and the minimum required for an acceptable crop yield. Assumptions are necessary on yield/soil depth relationships, but a table of initial recommendations is provided giving minimum depths of soils for a range of common crops and land use in Zimbabwe. These recommendations are based primarily upon field experience. As an illustration of the use of soil life-span, the granitic sands in a part of the Sabi Valley in S.E. Zimbabwe are calculated to have no more than 10 years of productive potential for maize at present rates of erosion. A traditional grain such as sorghum could probably be grown for the next 30 years.
