The compost heap should have free contact with the earth so that the various organisms present in the soil can readily migrate up. If the compost heap is built directly over growing vegetation, particularly grass, an acid layer forms, which acts as a barrier to the entry of earthworms and microorganisms. A foundation of concrete or a similar material can be used to provide a means of salvaging any liquid run-off from the compost heap . This liquid can then be used to maintain