Most soils have three major horizons — the surface horizon (A), the subsoil (B), and the substratum (C). Some soils have an organic horizon (O) on the surface, but this horizon can also be buried.

A soil profile is a vertical section of soil like the diagram above. It allows you to examine the structure of soil. A soil profile is divided into layers called horizons. The A horizon is where there is most soil life and is sometimes called topsoil.

A vertical section through different layers of the soil is called the soil profile. Each layer differs in feel (texture), colour, depth and chemical composition. These layers are referred to as horizons.

Key steps

1. Humus is a nutrient rich material great for adding to soil.
2. You create humus by creating a compost heap.
3. Add horse manure but no other animal faeces.
4. Turn it regularly.
5. Make sure it is damp, but not wet.
6. Humus is a dark, spongy, jelly-like material.

Use approximately 1 wheelbarrow full of humus for every 5×5-foot section of soil to be treated, or about 1 cubic foot or humus for every 25 square feet or soil. You can add more as desired without causing any harm, but using less than the suggested amount may result in reduced plant vitality.

Compost is the black dirt, or “black gold” as we like to call it, created from the decomposition of the organic matter that we contribute, whether that be leftover food or yard waste. Compost literally takes years to fully decompose into a humus state. When the compost is fully decomposed it will then be 100% humus.

Typically soil in a home landscape is compacted so to reduce compaction, regularly add humus by spreading mulch or organic material on bare soil in beds and under trees and shrubs. Dig in compost, peat moss or the like into garden beds when planting to improve aeration.

Mulch is any material spread on the soil surface that retains soil moisture, prevents weeds, and enriches soil with humus as it decomposes. The etymology of the word “mulch” makes it sound more like decomposing organic matter or humus than mulch. As mulch breaks down, a thin layer of humus will form.

One of the most important functions of humus is that it makes the soil more porous, improving soil aeration, infiltration and drainage. This function of humus improves the structure of the soil and in conjunction with humus’s capacity to retain important nutrients, humus rich soil helps plant grow more easily.

Humus is not fertilizer.

(a) The presence of humus ensures that the nutrients of the dead plants and animals are released into the soil. From there, these nutrients are again absorbed by the roots of the living plants.

What’s the difference between organic material and organic matter? Organic material is anything that was alive and is now in or on the soil. For it to become organic matter, it must be decomposed into humus. Humus is organic material that has been converted by microorganisms to a resistant state of decomposition.