Low chroma matrix
When decoloration is so intensive that it invades the total groundmass of the soil, the latter presents gray colors with more or less bluish, greenish or yellowish shines.
Conditions of hydromorphism
It represents the most intense hydromorphic conditions and occurs in horizons which are the whole year saturated with water, or at least the largest part of it.
Under these conditions (provided sufficient organic matter is present and the water is poor in oxygen) the environment will be really reducing. All Fe and Mn present will be reduced to Fe++ and Mn++, provoking its redistributions through the soil, giving rise to gray, more or less greenish or bluish components, with low chroma. These horizons consist principally of clayey phyllosilicates with Fe++, iron carbonate (siderite) or complex hydrated phosphates (vivianite).
Horizons with hues of 5Y or more yellowish, and chroma of < 2, or better < 1, are indicators of an intense hydromorphism, characteristic for soils which are (almost) permanently saturated with water.
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