5.1.3—Soil profiles and horizons

A soil profile records long-term processes with depth: upper horizons are usually richer in organic matter, while deeper horizons show mineral movement, accumulation and parent material.

Interpret colour, texture, roots and translocation together. For a fair investigation, sample the B horizon from one managed garden or field and one natural ecosystem at comparable depth and sample size; compare texture, organic matter, NPK, aeration, drainage and water retention.

The mass lost after heating estimates burned organic matter. Use dry samples and the same procedure for both soils; the estimate does not by itself identify which carbon compounds were present.

Colour alone cannot identify a horizon process or carbon content; combine profile observations with measured texture and chemistry.