If the lumps are left for 24hrs the dispersive character of the subsoil can be seen. Most subsoil in Western Australia are slightly less acid than the top soils and will not affect the pH of the topsoil markedly. If these chemicals have been used on the soils, there might be some accumulation on alkaline subsoils. This needs to be tested. The amount of subsoil that is applied will determine the clay content in the top 100mm of topsoil.
Some machines have difficulty spreading at lower rates but are large in capacity.
These can spread more subsoil for a cheaper or equivalent cost including the extra smudging cost.