___________________________________ TITLE 5 SOIL ___________________________________ EVALUATOR ___________________________________ CERTIFICATION TRAINING ___________________________________ ___________________________________ SOIL HORIZONS AND LAYERS ___________________________________ ___________________________________ Prepared for: Commonwealth of Massachusetts Department of Environmental Protection By L.A. Spokas, PhD, Stockbridge School of Agriculture University of Massachusetts Amherst Presented by: New England Interstate Water Pollution Control Commission ___________________________________ ___________________________________ SOIL PROFILE DESCRIPTIONS ___________________________________ Soil Profile: A vertical section of the soil extending through all its horizons and into ___________________________________ the parent material. Soil Horizon: A layer of soil, approximately ___________________________________ parallel to the surface, having distinct ___________________________________ characteristics produced by soil-forming processes. ___________________________________ Soil Layer: A layer in the soil deposited by geologic forces (e.g., wind, water, ice) and not related to a soil-forming process. ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ SOIL HORIZON AND LAYER DESIGNATIONS ___________________________________ ___________________________________ Three kinds of symbols are used in various combinations to designate soil horizons and ___________________________________ layers: CAPITAL LETTER, lower-case ___________________________________ letters, and Arabic numerals (1,2,3…) ___________________________________ Master Horizons and Layers: ___________________________________ O,A,E,B,C, and R are symbols that designate major breaks in the soil and are base symbols to which other characters may be added to describe the soil in more detail. ___________________________________ ___________________________________ A ___________________________________ ___________________________________ Bw ___________________________________ ___________________________________ ___________________________________ C ___________________________________ SOIL HORIZON AND LAYER DESIGNATIONS ___________________________________ Subordinate Distinctions: ___________________________________ Lower-case letters are used as suffixes to designate ___________________________________ specific kinds of master horizons and layers. Ap, plowed A horizon ___________________________________ Bh, B horizon with an accumulation of organic matter Bhs, B horizon with an accumulation of organic matter ___________________________________ and “sesquioxides” (iron and aluminium) Bw, weathered B horizon ___________________________________ Bs, B horizon with only sesquioxides Cd, dense C horizon (usually till) Cg, “gleyed” C horizon – typically in wetlands ___________________________________ SOIL HORIZON AND LAYER DESIGNATIONS ___________________________________ Vertical Subdivision: Two or ___________________________________ more horizons or layers designated by a single ___________________________________ C combination of letters which needs to be subdivided. ___________________________________ C2 Arabic numerals are used, ___________________________________ C3 and generally follow all letters. Within a C-Layer, for example, ___________________________________ C4 successive C-layers should be designated as C1, C2, C3, etc. C5 ___________________________________ SOIL HORIZON AND LAYER DESIGNATIONS ___________________________________ Vertical Subdivision: Two or ___________________________________ more horizons or layers designated by a single ___________________________________ combination of letters which needs to be subdivided. ___________________________________ C Arabic numerals are used, ___________________________________ and generally follow all letters. Within a C-Layer, for example, ___________________________________ successive C-layers should be designated as C1, C2, C3, etc. C2 ___________________________________ SOIL HORIZON AND LAYER DESIGNATIONS ___________________________________ When lithological ___________________________________ discontinuities occur in a profile, Arabic numerals ___________________________________ are placed in front of all letters starting at the first discontinuity. ___________________________________ ___________________________________ For example sequence A, Bw, C, 2C indicates that ___________________________________ the 2C horizon has formed in a parent material different from the C. ___________________________________ ___________________________________ ___________________________________ Horizons followed by the letter “b” are buried ___________________________________ horizons By definition of Title 5 - ___________________________________ all material above an “A” horizon is fill, and Fill ___________________________________ must be removed ___________________________________ Ab ___________________________________ ___________________________________ MASTER HORIZONS -O ___________________________________ O Layer with predominantly ___________________________________ organic matter ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ O-HORIZON ___________________________________ O-horizons are layers dominated by organic matter. ___________________________________ Greater than 20-30% organic matter by weight ___________________________________ Dark, nearly black or black, color (note: colors can be misleading and should only ___________________________________ be used when other field criteria are observed). ___________________________________ Weak strength, greasy feel, light weight when dry, high fiber content. Typically a surface horizon; if buried, often indicates disturbance. SUBORDINATE DISTINCTIONS ___________________________________ OF O-HORIZONS: ___________________________________ ___________________________________ Oi - Slightly decomposed organic ___________________________________ material: fibric ___________________________________ Oe - Organic material of intermediate ___________________________________ decomposition: hemic ___________________________________ Oa - Highly decomposed organic material: sapric ___________________________________ ___________________________________ A-HORIZON ___________________________________ The A-horizon is commonly referred to as the topsoil, and typically ranges ___________________________________ from 8-20 cm in thickness. It is a ___________________________________ mineral horizon that formed at the ___________________________________ surface or below an O-horizon, and is characterized by an accumulation of ___________________________________ humified organic matter intimately mixed with the mineral fraction. ___________________________________ A-HORIZON ___________________________________ Mineral soil material ___________________________________ Mixture of well decomposed organic ___________________________________ matter and mineral ___________________________________ material. Surface mineral horizon. ___________________________________ Typically dark in color – ___________________________________ characteristically darker than underlying horizons due to a relatively high organic matter content. ___________________________________ A-HORIZON ___________________________________ ___________________________________ Suborinate Distinctions of A-horizon: Ap- Plowing or other disturbance. ___________________________________ This symbol is used to indicate disturbance of the surface layer by ___________________________________ cultivation. ___________________________________ ___________________________________ ___________________________________ ___________________________________ E-HORIZON ___________________________________ The E-horizon is a mineral horizon in the upper part of the ___________________________________ soil, typically underlying an O or an A-horizon. ___________________________________ It is a light-colored, leached horizon often associated with ___________________________________ woodland areas. ___________________________________ E-horizons range from not being present in the soil to thicknesses of about 10 – 20 cm. ___________________________________ E-Horizon Field Criteria: ___________________________________ Commonly near the surface, below an O or A- ___________________________________ horizon and above a B-horizon Generally lighter in color than overlying organic ___________________________________ and/or A-horizons and underlying B-horizon ___________________________________ Formation: Weak organic acids strip coatings ___________________________________ from sand grains, and material is leached down ___________________________________ into the subsoil . Light color is due to natural color of the dominant quartz sand grains. ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ B-HORIZON ___________________________________ ___________________________________