NOTE

Abstract

Estimates by 10 operators of illuvial clay in thin sections of six B horizons differed widely; coefficients of variation ranged from 39 to 64 percent. The results cast serious doubt on the usefulness of oriented, apparently illuvial, clay in thin sections as a quantitative criterion of argillic horizons unless steps are taken to ensure a greater degree of uniformity of estimates. Estimates by 10 operators of illuvial clay in thin sections of six B horizons differed widely; coefficients of variation ranged from 39 to 64 percent. The results cast serious doubt on the usefulness of oriented, apparently illuvial, clay in thin sections as a quantitative criterion of argillic horizons unless steps are taken to ensure a greater degree of uniformity of estimates. © Williams & Wilkins 1980. All Rights Reserved.