Application of Gypsum to Control P Runoff from Poultry Litter Fertilization of Pasture.

This paper will discuss the utilization of gypsum (CaSO₄ ^.2H₂O) to reduce P losses from surface runoff when poultry litter is used as a fertilizer source in agriculture. Utilization of poultry litter as a fertilizer source is common in regions with intense poultry production. While poultry litter is an excellent fertilizer for pasture production, there are environmental risk associated with its use. The largest concern is the increased risk of nutrient losses in runoff, especially P. Several studies have shown that gypsum can be used to reduce environmental degradation from agriculture. Gypsum has been used as an agricultural soil amendment for over 250 years as a soluble source of calcium and sulfur for crops and has been shown to improve soil physical and chemical properties. New sources of gypsum such as flue gas desulfurization (FGD) gypsum are resulting in increased gypsum availability. FGD gypsum is a manufactured gypsum by-product of the coal-fired combustion process from scrubbers that remove sulfur dioxide (SO₂) from the flue gas stream when coal is burned to generate electricity. This paper will discuss the environmental benefits of using gypsum as a co-application with poultry litter which include reduced soluble P and As in runoff. For example, a rainfall simulation study on a Coastal Plains soil has shown a 51% reduction in total dissolved P load over several years.