Clay Migration in the Formation of Argillic Horizons in Soils Developed under Varying Moisture Regimes

Five pedons representing major soil groups of the NW India were subjected to clay migration studies involving the use of thin-sections, contact-capillarography and the clay translocation as observed on the chromatographic paper and on the Metricel Gelman membrane. The results generally reveal a very low effective clay mobility in Udic soils having thick, continuous and strongly oriented argillans, and moderate to high clay mobility in Ustic soils where clay cutans are either not observed or are weakly oriented. The potentially mobile, that is dispersible, clay is the highest in Ustic soils and the lowest in Udic soils having optimum conditions for clay translocation suggesting that the highly birefringent argillans in the Udic soils are not a definite proof for the present-day illuviation but could be taken to indicate the past illuviation process.