Criteria and Mathematical Expressions for Evaluating an Illuvial Accumulation of Clay in Luvisols

Abstract

One of the most important aspects of soil development is to establish the initial states of the parent material and of the soil material at each position of the soil profile. Luvisols have a higher clay content in the argic horizon than in the eluvial horizon, as a result of pedogenetic processes, especially clay migration. The illuvial nature of the argic horizon may be established using a lot of criteria and the quantity of migrated clay can be calculated with mathematical expressions. For Luvisols situated in the south-western zone of Romania, named region Banat, have been effectuated the next analysis: particle-size, chemical, mineralogical for index minerals present in the nonclay fraction, mineralogical for clay fraction – X-ray, differential thermal and infrared. Calculations for the amount of clay formed at each horizon or less at each horizon were made using some mathematical expressions. Luvisols cover in the south-west of Romania an area of 427779 ha, representing 26.51% from the total area of 1,613,538 ha. The scientific research was made on an Albic Luvisols – Lalasint, formed from a Cretaceous flysch, composed of conglomerate and silicate with pieces of quartzite. Calculation of the fine sand/coarse sand ratio, the quartz and feldspar content at each horizon, the change of index minerals with depth, and the eluviation index (k) calculated with the mathematical expressions, allowed to establish the quantities of clay migrated on the soil profiles and the uniformity of the soil material. In the soil type the soil materials were initially bistratified and during soil forming processes clay migrates down into an argic horizon.