Clay and iron oxide contents of prismacutanic B, G, soft plinthic B, and E horizons described during the land type survey of South Africa

摘要

Humans organise their environment, including soils. With soil classification the challenge is to consistently differentiate between soils. This study was therefore initiated to summarise selected properties of the prismacutanic B, G, soft plinthic B,and E horizons, described during the land type survey of South Africa, and to define quantitative differentiating criteria for these horizons. A total of 1 181 soil profiles, comprising 299 Sterkspruit, 331 Estcourt, 49 Katspuit, 257 Kroonstad, 103 Westleigh and 142 Longlands soils were extracted from the database and used in the analysis. Based on the analysis, we propose the following criteria be used to quantitatively differentiate between the studied horizons: E horizons have <1.0% Fe and <16% clay;with practically no change in either Fe or clay content from the overlying horizon; with a Fexlay ratio <0.04. Soft plinthic B horizons have >1.0% Fe and <25% clay; the clay increase from the overlying horizon is >1.5 times; with a Fexlay ratio >0.04. Ghorizons have >1.0% Fe and >25% clay; the clay increase from the overlying horizon is >1.0; with a Fexlay ratio <0.04. Prismacutanic B horizons have >1.0% Fe and >25% clay; the clay increase from the overlying horizon is >2.5; with a Fexlay ratio <0.04.