Clay differentiation in initially homogeneous substrates upon long-term field experiments

Experimental data attesting to considerable spontaneous differentiation of the soil profile by the content and mineralogical composition of the clay f raction in the course of a 23-year-long field trial are analyzed. The exper iment has been performed for three initially homogeneous substrates: loess soil, alluvial soil, and sandy soil. The highest relative rate of clay loss from the plow horizon is registered in the loess soil enriched in smectiti c minerals. This loss reaches 0.9% of the initial clay content per year, or 20% per 23 years.