An epipedon is diagnostic surface horzon in Soil Taxonomy
The general rule of thumb is to determine the properties after mixing the soil to a depth of 18 cm. An absolute exception to this 'rule of thumb' is soil structure, and it is never to be homogenized or mixed.
The percent saturation must be equal to, or greater than, 50. %BS ≥ 50
The percent organic carbon (%OC) must be equal to, or greater than, 0.6. %OC ≥ 0.6
The soil cannot be both massive and have a dry consistence of hard or harder.
The soil color value must be less than, or equal to, 5 dry. ≤ 5/
The soil color value must be less than, or equal to, 3 most.
The soil color chroma must be less than, or equal to, 3 most. ≤ 3/3
Minimum thickness generally between 18 and 25 cm.
A P2O5 less than 250 ppm. P2O5 < 250 ppm
The soil must be moist greater than 3 months.
The soil must have an n less than 0.7. n < 0.7
Like Mollic except the percent base saturation is less than 50%.
Epipedon that does not meet the requirements of the other epipedons.
If the epipedon is stripped there is none.
Epipedon of organic soil material 20 to 40 cm thick, unless composed of sphagnum fibers, then 20 to 60 cm thick. May consist of mineral soil material if plowed.
Epipedon of organic soil material saturated less than 30 days, ≥ 15cm thick, unless composed of sphagnum fibers then ≥ 20 cm.
Epipedon like mollic except for P2O5 content and duration of available moisture.
Epipedon with andic soil properties, > 30 cm thick within 30 cm of the soil surface, value/chroma < 2/2 moist, > 4% OC and average > 6% OC, melanic index < 1.70.
Epipedon of human-induced horizon from manuring and spading.