Soils with argillic horizons

The progressive development of such argillic features with increasing weathering intensity is commonly documented in soil chronosequence studies (Harden, 1990). An example of the development of argillic horizons is shown for the Merced chronosequenence in Figure 18 (White et al., 2003). Over a time span of... 

Ultisols. Mineral soils that have an argillic horizon with a base saturation of <35% when measured at pH 8.2. Ultisols are strongly leached, acid forest soils with relatively low native fertility. They are found primarily in humid temperate and tropical areas of the world, typically on older, stable landscapes. These soils are characterized by an accumulation of clays in the subsurface horizon and exhibit strong yellowish or reddish colors resulting from the presence of iron oxides. Ultisols are divided into five suborders Aquults, Humults, Udults, Ustults, and Xerults. 

Nitosols (N) Other soils having an argillic B horizon with a clay distribution where the percentage of clay does not decrease from its maximum amount by as much as 20% within 150 cm of the surface lacking plinthite within 125 cm of the surface lacking vertic and ferric properties ... 

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