Soil Horizons and Erosion

Order of soil horizons from top to bottom

O, A, E, B, C, R

O Horizon (Humus)

Surface litter, like leaves and other decaying matter

A Horizon (Topsoil)

Mixture of organic materials with minerals

E Horizon (Eluviated)

Zone of leaching, nutrients from upper horizons moves to lower horizons

B Horizon (Subsoil)

Zone of Accumulation where minerals such as iron and other nutrients accumulate

C Horizon (Parent Material)

The rocks that are broken down to create soil

R Horizon (Bedrock)

Solid rock that lies beneath the parent material and soil

Nutrient Depletion

Repeatedly growing crops on the same soil, removes key nutrients (N, P, Na, Mg) over time.

Reduces ability to grow future crops

Compaction

Compression of soil by machines (tractors, bulldozers, etc.), grazing livestock, and humans reduces the ability to hold moisture.

Dry soil erodes more easily & supports less plant growth and root structure, leading to more erosion

Loss of topsoil

Tiling (turning soil for agriculture) + loss of vegetation disturb soil and make it more easily eroded by wind and rain

It also dries out soil, removes nutrients + soil organisms that recycle nutrients