Several compositions of matter have been discovered that can be used in the manufacture of slow-release fertilizers that contain all of the essential elements needed by plants and humans. Slow-release fertilizers manufactured with these formulations can be used on mineral stressed soils to increase the quality and production of food crops grown on them. Additives, including phosphogypsum, silica sand, natural gypsum, clay, and coal dust, facilitate the timing of the release of the essential elements into the soil.
Palmer, Jay W. and Kay, Heidi, "Slow-release (GSSP) fertilizer" (2010). USF Patents. 492.
University of South Florida