A REAPPRAISAL OF SOIL MAPPING IN AN AREA OF SOUTHERN SCOTLAND. PART I THE RELIABILITY OF FOUR SOIL MAPPING UNITS AND THE MORPHOLOCICAL VARIABILITY OF THEIR DOMINANT TAXA

A two stage random sample survey was made to study the composition of four common soil mapping units already mapped in the Central Lowlands of Scotland. The four mapping units were sampled at densities proportional to their mapped area. In terms of their A horizon textures, the mapping units had percentage reliabilities of 84, 96, 93 and 97 and drainage class reliability scores of 70, 80, 72 and 70. On the basis of taxonomic units within the mapping units, percentage reliabilities ranged from 43–66 but no minor constituent soil exceeded 16 per cent in any of the units studied. Although complex according to currently accepted guidelines, such mapping units should be named according to the dominant taxonomic unit. Errors of identification due to inadequate definitions of taxonomic units have contributed to some of the low levels of reliability of taxonomic units within mapping units and soil taxa should be defined more precisely in Scotland. Means and variances of the taxonomic units, upon which the above named mapping units are based, indicate that the four taxonomic units (and hence also mapping units) under study are not equally variable in the area of investigation.