OMRI Certified Organic Wiggle Worm Soil Builder is just what you need to amend your depleted garden soil or raised bed media. 40 lb bag. Why the excitement over WORM CASTINGS? Research shows that compared to the soil itself, worm castings are definitely higher in bacteria and organic matter, total and nitrate nitrogen, exchangeable calcium and magnesium, available phosphorus and potassium, pH and percentage base saturation and cation exchange capacity. In other words, worm castings are a sterile, odorless means to condition your soil and an organic and natural way to provide your plants with the nutrients they need, when they need them. Scientists have shown that worm castings work extremely well in promoting lush plant growth, but to this day, they still are not exactly sure why Earthworm castings work as well as they do. It just goes to show that Mother Nature knows best.