Can I put clay soil, old soil, or potting soil from pots into my compost?
Certified GKH Gardening Expert
Yes, as long as the soils have not had diseased plants growing in them in the last few years. Soil will help add beneficial microbes to your compost pile. Here is more information on making compost mixes:
Soil can be added as up to 1/4 of the compost pile, with the rest divided between "green" and "brown" material.