Friday, January 9, 2009

Soil Horizons

A soil horizon is a specific layer in the soil which measures parallel to the soil surface and possesses physical characteristics which differ from the layers above and beneath.

The term 'horizon' describes each of the distinctive layers that occur in a soil. Each soil type has at least one, usually three or four different horizons and these are described by soil scientists when seeking to classify soils (Soil-Net). Horizons are defined in most cases by obvious physical features, color and texture being chief among them. These may be described both in absolute terms (particle size distribution for texture, for instance) and in terms relative to the surrounding material, ie, ‘coarser’ or ‘sandier’ than the horizons above and below.

O) Organic matter: Litter layer of plant residues in relatively undecomposed form.

A) Surface soil: Layer of mineral soil with most organic matter accumulation and soil life.

B) Subsoil: Layer of alteration below an "E" or "A" horizon. This layer accumulates iron, clay, aluminum and organic compounds, a process referred to as illuviation.

C) Substratum: Layer of unconsolidated soil parent material. This layer may accumulate the more soluble compounds that bypass the "B" horizon.

These horizons were on full display throughout the installation of the mainline on the course. It was amazing to see how different the A horizon layer was from hole to hole. During construction of the golf course the topsoil (A horizon) was stripped off and stockpiled for redistribution after the rough shaping was completed.

Distinctly Visible A Horizon Layer

Weather it occurred in the final shaping or from the spreading of the topsoil, the A horizon layer varies significantly. Some areas we have only four inches whereas other areas have as much as ten inches. Seeing some of these areas first hand helped explain why the turf consistently struggles in certain areas no mater how much the surface is modified.