For purposes of this part, the following definitions shall apply:

1. (a) “A horizon” means the surface soil or mineral soil, formed at the surface or below an O horizon, little remnant rock structure, and one or more of the following:

   1. (1) accumulation of humified organic matter but dominated by mineral matter, and not dominated by E or B horizon properties;
   2. (2) properties resulting from cultivation, pasturing, or similar disturbance; or

   3. (3) morphology resulting from surficial processes different from the underlying B or C.

      The term excludes recent eolian or alluvial deposits that retain stratification;

2. (b) "Ap horizon" means an A horizon that has been subject to tillage or other disturbance of the surface layer;
3. (c) “Aquic conditions” means continuous or periodic saturation and reduction, as indicated, except in Histosols, by redoximorphic features, which can be verified, except in artificially drained soils, by measuring saturation and reduction;
4. (d) “B horizon” means a layer of soil or soil material approximately parallel to the land surface that forms below an A, E, or O horizon;
5. (e) “Bs horizon” means a B horizon with an accumulation of illuvial, amorphous, and dispersible organic matter and sesquioxides;
6. (f) “Bh or Bhs horizon” means a B horizon with an accumulation of illuvial, amorphous, and dispersible organic matter and sesquioxides. The sesquioxide component coats sand and silt particles. The symbol “h” is used in combination with “s” as Bhs if the amount of sesquioxide component is significant but value and chroma of the horizon are 3 or less;
7. (g) “Chroma” means the relative purity or saturation of a color, or its intensity of distinctive hue as related to grayness. Chroma is one of the 3 variables of color;
8. (h) “E horizon” means a mineral soil horizon in which the main feature is loss of organic matter, silicate clay, iron, or aluminum, or some combination of these, leaving a concentration of sand and silt particles;
9. (i) “Gleyed matrix” means a soil horizon matrix color resulting from prolonged periods of wetness that makes up more than 50% of the horizon or subhorizon where iron has been reduced and removed, or where saturation with stagnant water has preserved a reduced state;
10. (j) “Matrix” means the natural soil material composed of both mineral and organic matter;
11. (k) “Mineral soil surface” means the top of the uppermost soil horizon consisting of mineral material with less than 12 to 18 percent of organic carbon, depending on the clay content;
12. (l) “Mottles” means the redoximorphic features comprising spots of contrasting colors in a horizon, with both high chroma and low chroma represented in the variegated colors;
13. (m) "O horizon" means organic soil materials other than limnic materials with the mineral fraction a small percent by volume and less than 80% by weight;
14. (n) “Redox depletions” means bodies of chroma 2 or less, having value 4 or more where iron-manganese oxides and clay have been stripped;
15. (o) “Spodic horizon” means a subsurface layer of soil characterized by the accumulation of aluminum oxides, with or without iron oxides and organic matter; and
16. (p) “Value” means the relative lightness or intensity of color and is approximately a function of the square root of the total amount of light. Value is one of the 3 variables of color.

Source. (See Revision Notes #1 and #2 at chapter heading for Env-Wq 1000) #11184, eff 10-1-16; ss by #14486, eff 2-1-26, EXPIRES: 2-1-36