Mother Earth? Worm Castings are an all-in-one soil amendment. Earthworms convert organic matter into humus, which is good for amending soils. Our worms are carefully fed with composted forest humus, corn meal, greensand, azomite, gypsum, oyster shell flour, walnut meal and alfalfa meal to ensure the best quality castings. Add Mother Earth? Worm Castings to any potting soil as an amendment or use as a primary ingredient in compost tea.