QUESTION: What characteristics differentiate these two horizons?
A3--11 to 19 inches; yellowish brown (10YR 5/4) loam; dark yellowish brown (10YR 4/4) moist; strong medium angular blocky structure; hard, friable, slightly sticky, and slightly plastic; few very fine roots; common very fine and few fine tubular pores;common fine faint very pale brown (10YR 7/3) iron depletions; moderately acid (pH 5.6); abrupt smooth boundary.
2Bt1--19 to 38 inches; yellowish brown (10YR 5/4) clay; dark yellowish brown (10YR 3/4) moist; strong coarse prismatic structure; extremely hard, firm, moderately sticky and moderately plastic; few very fine roots; common very fine and few fine tubular pores; many moderately thick clay films; slightly acid (pH 6.2); clear smooth boundary.
The A3 has less clay (loam texture class) than the Bt (clay texture class)
The A3 is slightly darker when moist (value of 3 not 4).
The structural units of the A3 are smaller (medium vs coarse).
Structure type is prismatic in the Bt compared to blocky in the A3.
The higher clay content of the Bt compared to the A3 is supported by the harder consistence when the Bt is dry or moist and more sticky and more plastic consistence when the Bt is wet.
Clay films in the Bt indicate accumulation of clay that has moved from the overlying horizons.