Worm castings are like a probiotic for your soil. As worms digest organic materials, they refine them, breaking down nutrients and trace elements to the most usable forms for plants. Worm castings contain 50% more humus, seven times the amount of nitrogen and five times the amount of phosphorus and potassium contained in regular topsoil. Humus is organic material rich in microorganisms that increase soil fertility. Worm castings hold about three times their weight in water. This moisture retention helps your plants stay hydrated, even in times of drought. They also contain high levels of chitinase, a natural insect repellent. When used properly, worm castings help to repel chewing and sucking insects like aphids, whiteflies and hard-shelled plant bugs. Worm castings also make soil more porous, improving soil aeration, infiltration and drainage. Healthy soil = healthy plants!