How to Name Soil Horizons

1. How to Name Soil Horizons “The Dirt on Soils” 101 2-09

2. K.I.S.S. 1 • Horizons must be 8 cm or more thick. • Identify the A horizon(s), follow it down until the color lightens or the clay decreases or increase noticeably. • Now go find the clayiest subsoil horizon that has structure and call it a B. If there is no change in clay in the subsoil, choose the reddest subsoil horizon. • Next, identify the horizons between the A(s) and the B you just identified. If there are clay films in it, call it a B, regardless of color. If no clay films and the color changes to be in the upper left corner starting with the 5/3 chip, and it has less clay than the B below, call it an E.

3. K.I.S.S. 2 • If there are still horizons between the A and B, or the E and B, or the A and E, call it transitional and list the letter of the one it most resembles first (EX: a horizon > 8cm thick lies between A and B, has more clay than the A and not as dark as A, so AB). • Now follow down from where you had the clayiest (or reddest horizon). If that horizon has clay films, call the rest of the horizons B horizons as long as they have clay films. If there were no clay films, looks for a loss of redness.

4. K.I.S.S. 3 • Now go to the lowest horizon to be described. • Does it have any soil structure? If so, put a B on it. If no soil structure, put a C on it [unless it is hard bedrock (R)]. Note: Really really sandy soils have no structure but still have “color” B horizons. • Does it have >= 50% rock structure or flooding-strata? If so, put a C on it. • Even if it has that much rock or flood structure if it has some B material (by color or texture or structure), add a B to it also. • If it has clay films, and the clay content is about as high as any horizon in the soil, just call it another B. but if the clay content has decreased or if the clay films are fewer, or both, add a C to it.

5. K.I.S.S. 5 • Only call something B/E or E/B if it is horizontal red stripes in a really really sandy soil; or if the B pockets where it has dissolved into E horizon in big parts. Add t to the B part if needed. • ORDER: • You should have already tacked on the lowercase b’s and g’s where needed. • Add numbers at the end if two identical horizons are touching each other. • Add numbers in front of the second parent material, and the third of that exists. • Add a prime right after the uppercase letter if identical horizons are not touching.

6. K.I.S.S. 4 • Now for the lowercase letters: • If the A horizon has an abrupt lower boundary somewhere between 15 and 35 cm deep, add a p. • On any horizon, if you see any white precipitate, and it bubbles when HCl is added, or if the horizon bubbles anywhere, add k. If you see clay films or clay bridging in a B or BC, add a “t’ • Check sticky clayey B horizons for slickensides, add ss. • Check for speckled, calico missiles surrounded by gray striped ribbons, add an x if the missile part does not easily fall apart into soil structure with fine roots between. Should be hard to dig. • If you see a darker layer >= 50cm down, and it is not really really sandy, call it an Ab. Add a b to all horizons below that except a C or R. • If the B subsoil is not in a floodplain, is really really sandy, has a brown or black subsoil under an E horizon, add h for black and hs for brown. Add just s for anything redder beneath (if any). • If the soil has a water table and a wet horizon gets a matrix color of value 4 or more, chroma 2 or less, add a g. Only add a g to an A horizon if the colors are right and it has red redox in it. • Only C horizons can get an r, to signify at least 90% rocks in place and root-limiting. • Dense lower subsoils are hard to dig and look/feel like concrete. Call them Cd. • Only if the horizon is redder than some other part, but does not fit anything described above, call it Bw. Never mix w with other letters except g or b. Never call a Bw that is touching a Bt or Bh or Bhs. Call it a tansitional BA if above and BC if below.

7. t t B/E B&E Examples • Combination horizons • This OK: • or B/E t E & B t Stripes are clay bands light colors are E sands

8. Minimum Thickness Upland Unplowed Thickness* Plowed ThicknessUneroded ErodedYou can assume that a thin E once existed in these soils. 8 cm If they combine two thin horizons, name it a transitional horizon and describe the majority A 8 cm E < 8 cm BE 8+ cm Bt > 8 cm Ap Ap BE 8+ cm Bt > 8 cm BE 8+ cm Bt > 8 cm • Thicker in floodplains and wetlands and • some footslopes

9. Follow this example: Before ….. After A A1 A A2 E E Bh Bh E E’ Bh B’h1 Bh B’h2 E E’’ Bh B’’h C C

10. p AE Ab BC Bwb1 Bwb2 g r Examples Upland or footslope Floodplain Sandy Coastal Plains