Using biosolids (treated sewage sludge) as a base on sports fields builds the health of the soil which builds great grass and turf. Biosolids help create a softer, more spongelike soil that actually helps reduce injuries. Soil structure and health are critical. Biosolids are a great foundation when building a new sports field or top-dressing existing fields. They have a host of micro and macro nutrients, retain water, and can actually remediate contaminants in urban soils with a tremendous protective power that keeps contaminants locked in the soil (not available to plants).