Soil Horizons (O and A)

🔷A Soil Profile is a map of the distinct layers or HORIZONS in the ground of different materials… (organic matter, clay, humus, etc.)

🔷 “Soil scientists have attached a letter or combination of letters to each horizon that appears in any typical soil profile. For the gardener, the top horizons, the O and A, are really the only ones that count”

-Teaming with Microbes

Oi = FIBRIC - contains organic material that can still be specifically identified.

Oe = HUMIC/HEMIC - Has experienced more decay, and while materials are identifiable like let’s say plant matter, you cannot tell which specific plants are involved.

Oa = SAPRIC - Is where the organic material has decomposed so much that you cannot tell its origin; it could be from plants or from animal matter.

A = (Topsoil) Located directly below the O layer; This layer is made up of minerals and decomposed organic matter and very dark in color. This is the layer that many plants roots grow in!