Only the percent sand, silt, and clay are used for soil
textural determination, material larger the 2 mm are
described as rock fragments. Rock fragments are described
separately on a pedon description. Textural modifiers are
used when rock fragments occupy more than 15 percent by
VOLUME of the horizon (gravelly sandy loam for example).
Organic material and organic horizons are excluded from
soil textural determination. Organic horizons (Oi, Oe, Oa)
are described based on the degree of decomposition (fibric,
hemic, sapric, etc.) and other factors. Mineral horizons
that have considerable (> 8%) organic matter can be
described with a mucky modifier (mucky silt-loam).
Importance: Soil texture is one of the most important
soil property particularly when dealing with water
movement through the soil. Soil mechanical and
engineering properties are also influenced by soil
texture.
