Can gypsum be applied on organic farms?
Commercial farmers, organic growers, home owners, turf managers and others can benefit from application of gypsum (calcium sulfate) in remediating salinity and sodium issues and improving soil structure. However they can’t all use the same sources or gypsum for all garden soils.
Mined gypsum can be OMRI® listed (Organic Materials Review Institute®). OMRI is a national nonprofit organization that determines which input products can be used in organic crop production. Many natural gypsum suppliers have gotten this certification. OMRI listed products can be used in certified organic operations under the USDA National Organic Program.
However, many sources of synthetic gypsum product can’t get an OMRI listing. Gypsum sourced from flue gas desulfurization (FGD) systems at electric power plants can carry some metals and is not OMRI listed. Other forms of synthetic gypsum include by-products of citric, lactic or phosphoric acid manufacturing plants, water treatment plants as well as recycling wall board.
An organic farmer or gardener creates compaction from trafficking or tilling that compresses the soil and destroys soil structure of the garden. These activities create poor drainage and aeration, soggy soils and reduced root growth. Manure, compost, peat moss and soil mulches and soil conditioners all help in building soil structure and help it resist compression and destruction.
Gypsum is another solution for reconditioning the soil, because this product can be spread on the surface of the soil and does not have to be incorporated since it is very soluble. Gypsum, once solubilized, penetrates clay particles in heavy soil or the layer of hard subsoil and loosens soil structure. This creates air and moisture slots that will loosen and break up the soil structure.
Mined gypsum can be used in organic production, but industrial by-products aren’t allowed.
Dr. Davidson posts articles on soil management and subjects to gypsum. If you have suggestions for topics or questions, feel free to contact him at [email protected] or call 402-649-5919.