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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #270279
Title: Land application of spent gypsum from ditch filters: phosphorus source or sink?

Author
item GRUBB, KAREN - National Institute Of Food And Agriculture (NIFA)
item MCGRATH, JOSHUA - University Of Maryland
item PENN, CHAD - Oklahoma State University
item Bryant, Ray

Submitted to: Agricultural Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2011
Publication Date: 8/12/2011
Citation: Grubb, K.L., Mcgrath, J.M., Penn, C.J., Bryant, R.B. 2011. Land application of spent gypsum from ditch filters: phosphorus source or sink?. Agricultural Sciences. 2(3):364-374.

Interpretive Summary: Agricultural drainage ditches can provide a direct connection between fields and surface waters, and some have been shown to deliver high loads of phosphorus (P) to sensitive water bodies. Filter structures containing P sorbing materials such as gypsum have recently been shown to be effective at removing P from ditch flow, but as the P content in the gypsum increases, the filter becomes less effective. The spent gypsum will eventually need to be replaced with fresh gypsum. We determined the effect of land-application of spent gypsum removed from such filters on soil P forms and concentrations. Soil type, time after application, gypsum rate, and P saturation level all had a significant impact on soil P forms and concentrations. However, it appears that land application of spent filter gypsum at realistic rates would have little effect on P availability to crops grown on amended soils.

Technical Abstract: Agricultural drainage ditches can provide a direct connection between fields and surface waters, and some have been shown to deliver high loads of phosphorus (P) to sensitive water bodies. A potential way to reduce nutrient loads in drainage ditches is to install filter structures containing P sorbing materials (PSMs) such as gypsum to remove P from ditch flow. The objective of this study was to determine the effect of land-application of gypsum removed from such filters on soil P forms and concentrations. Gypsum was saturated at two levels on a mass basis of P and applied to two soils of contrasting texture, a silt loam and a sandy loam and applied at both a high and low rate. The treated soils were incubated in the laboratory at 25 deg C, and samples were collected at 1, 7, and 119 days after initiation. Soil type, time after application, gypsum rate, and P saturation level all had a significant impact on soil P forms and concentrations. However, it appears that land application of spent filter gypsum at realistic rates would have little effect on soluble P concentrations in amended soils.