Soluble Calcium Amendment: Co-Application with Poultry Litter to Reduce P Loss Following Surface Application.

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 has been found to an excellent fertilizer for row crop and 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.  FGD gypsum is formed by scrubbers that remove sulfur dioxide (SO₂) from the flue gas stream when coal is burned to generate electricity so it does not become an atmospheric pollutant.  This paper will discuss the environmental benefits of using gypsum as a co-application with poultry litter.  The environmental benefits to be discussed include reduced soluble P and As in runoff from agricultural fields receiving poultry litter applications.  For example, a rainfall simulation study on a Coastal Plains soil has shown a 51% reduction in total dissolved P load over several years.