O horizon (organic layer)A surface layer of decaying leaves and other organic material.
A horizon (topsoil)The top layer of mineral soil, darkened by humus. Most roots grow here.
E horizon (leached layer)A pale layer that water has leached minerals out of. Not every soil has one.
B horizon (subsoil)Subsoil, where minerals washed down from above collect.
C horizon (parent material)Loose parent material, the least weathered layer of the soil.
BedrockHard, solid rock under the soil. Soil scientists letter it R.
Roots and brackets 3
Plant rootsRoots are thickest in the topsoil and thin out below it.
SolumThe upper, most weathered horizons, above the C horizon.
Soil profileA vertical section through all the horizons of a soil.
How this list was compiled: Every name checked on 2026-10-01 in at least two of these. (1) University of Hawaii at Manoa, College of Tropical Agriculture and Human Resources, Soil Nutrient Management for Maui County, Soil Profile, https://www.ctahr.hawaii.edu/mauisoil/a_profile.aspx (the profile as a vertical section; the master horizons O, A, E, B and C and what each is; the solum; bedrock under the profile; not every soil has every horizon). (2) NC State Extension, North Carolina Extension Gardener Handbook, chapter 1, Soils and Plant Nutrients, https://content.ces.ncsu.edu/extension-gardener-handbook/1-soils-and-plant-nutrients (topsoil, subsoil and parent material; roots are most concentrated in the topsoil; bedrock; humus). (3) Wikipedia, Soil horizon, https://en.wikipedia.org/wiki/Soil_horizon (O, A, E, B, C and R; topsoil for the A horizon and subsoil for the B; the R layer as bedrock, as in the USDA field book it quotes; the solum). Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry. Own original drawing; nothing is traced or copied. Licence: own work
How it works
A soil profile diagram to label: a block of ground cut straight down, from the fallen leaves on top to the bedrock below. Name each horizon, the roots and the two brackets.
Read the full guide
The horizons from the top down
The O horizon is the layer of fallen leaves and other organic material. Under it the A horizon is topsoil, dark with humus. The E horizon is a pale layer that water has leached. The B horizon, or subsoil, collects what washes down. The C horizon is loose parent material, and bedrock lies under it.
Draw and label the different horizons in a soil profile
To draw your own, rule a tall box and split it into bands. Letter them O, A, E, B and C from the top, with R for the bedrock. Not every soil has every horizon.
Topsoil, subsoil and parent material count as answers for the A, B and C horizons.
Questions and answers
What are the horizons of a soil profile in order?
From the top: O (organic material), A (topsoil), E (a leached layer), B (subsoil) and C (parent material). The hard bedrock under them is lettered R.
What is the difference between topsoil and subsoil?
Topsoil is the A horizon: it holds the most humus and the most roots. Subsoil, the B horizon, has less organic matter and collects clay and minerals washed down from above.
Does every soil have all the horizons?
No. Soil profiles differ from place to place, and not all of them contain every horizon. An E horizon, for example, is found only in older, well-developed soils.
What is the solum?
The solum is the upper part of the profile: the most weathered horizons, above the C horizon. On the drawing it is the shorter bracket, from the surface to the bottom of the subsoil.