It is best practice to detect on ploughed land, where the finds recovered are already removed from their original archaeological context. Recovering objects from below the plough soil can damage archaeological layers and should be avoided.
The differences in plough soil will vary according to the area and soil constitution. Plough soil is usually darker… and looks like topsoil.
You will notice a difference in soil density for a start, the sub soil is very compact. It will differ in colour.
“if in doubt, don’t dig it out”
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Subsoil will vary... Sandy soil, will look lighter and sandy’ier Clay soil, will look lighter and Clay’ier
Stoney soil……… if you get my drift
The action of the plough creates a pan, a hard surface that is difficult to penetrate. It is often at a lower level on land deep ploughed for potatoes.
Sub-soiling with a spike to a depth of approximately two feet on heavy land, helps to break up the solid pan & provide drainage. This sometimes bring to the surface grave goods that would not normally be in the plough soil.
