Worm castings are the richest natural fertilizer known to humans. Worm castings are an organic form of fertilizer produced from earthworms. Adding worm castings manure to the soil aerates and improves its overall structure while providing beneficial nutrients to plants. Worm Castings are packed with minerals that are essential for plant growth, such as concentrated nitrates, phosphorus, magnesium, potassium, and calcium. It also contains manganese, copper, zinc, cobalt, borax, iron, carbon, and nitrogen.