Not all soil scientists will write the exact same soil profile description , because their previous experiences will have been different, just like all artists will not paint the same picture when looking at the same landscape scene. Surface Horizons Surface soil horizons are mainly influenced by the addition of organic matter. In fact, the O horizon contains very little mineral soil. The i subscript, or Oi horizons, would be mainly undecomposed plant parts. The Oe horizon would be of moderate decomposition, and the Oa horizon would be almost completely decomposed.
Organic soils found in peat bogs also contain O horizons.
The A horizon is a mineral horizon that is dark in color due to the incorporation of decomposed organic matter, which coats the mineral soil particles with colloidal organic matter. In general, the darker the mineral soil, the greater the percent organic matter. When an A horizon is plowed, it is called an Ap horizon. Subsurface Horizons Subsurface horizons develop due to translocation, transformations and losses. The are zones of accumulations or changes in the parent material where color or structure develop.