RESURRECTION OF SOIL SURVEYS - A CASE-STUDY OF THE ACID SULFATE SOILSOF THE GAMBIA .2. ADDED VALUE FROM SPATIAL STATISTICS

Kriging is used to provide detailed quantitative information for a ran ge of soil characteristics across the floodplain of the River Gambia. Application of spatial statistics to a large area with a coarse grid o f data points produces spurious patterns unless the area is first part itioned into soil-geomorphic mapping units, each of which has a unique pattern of spatial variation. Even combining classical soil survey me thod with spatial statistics, the large short-range variability of aci d sulphate soils mc:ans that single factor maps conceal a large elemen t of uncertainty. A more robust procedure is to map the probability of occurrence of critical values of key characteristics.