Reductomorphic properties signify permanently wet conditions. They are expressed by neutral whitish/grayish or bluish and greenish ‘gley colors’ in more than 95 percent of the soil matrix. Near the capillary fringe (just above the water table), the (subsoil) layer with reductomorphic properties may include up to 5 percent oxidation colors, e.g., as mottles (around air pockets) or ‘root prints’ (former root holes lined with iron oxide).
Oximorphic properties indicate alternating reducing and oxidizing conditions, as occur near the capillary fringe and in the surface layers of soils with fluctuating groundwater depth. Oximorphic properties are expressed by reddish brown or bright yellowish brown mottles on aggregate surfaces and on walls of pores. Acid sulfate soils feature bright yellow mottles of jarosite KFe 3+3(SO 4) 2(OH) 6 (at pH < 3.5) or schwertmannite Fe 16+3O 16(OH) 12(SO 4) 2 (at pH 3.0–4.5).
- FAO, 2001. See under Gleysols In: Lecture notes on the major soils of the world. World Soil Resources Reports, 94. Rome: Food and Agriculture Organization of the United Nations, 334 pp.Google Scholar