WORM CASTINGS FOR SOIL AMENDING Michigan Mediums WORM CASTINGS set the standard for quality in vermicompost. Our worms are fed a fixed diet which create high quality castings excellent for use in soil building, top dresses and amending. Michigan Mediums WORM CASTINGS provides fungal activity for your soil and food for the microbiology. Just hand sprinkle on top of existing soil & water well. Helps plants absorb nutrients quicker. Mix small amounts into the soil. Increases plant vigor and health as well as adds to overall yield. Mix with Michigan Mediums COMPOST PLUS for a tea mix.