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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #331139
Title: Potential adherence of flue gas desulfurization gypsum to forage as a consideration for excessive ingestion by ruminants

Author
item Torbert, Henry - Allen
item Chaney, Rufus
item Watts, Dexter

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2016
Publication Date: 3/17/2017
Citation: Torbert III, H.A., Chaney, R.L., Watts, D.B. 2017. Potential adherence of flue gas desulfurization gypsum to forage as a consideration for excessive ingestion by ruminants. Journal of Environmental Quality. 46:431-435.

Interpretive Summary: Gypsum has long been used to improve soils and crop production, and its use has recently been encouraged by the USDA-NRCS for soil conservation through a new Conservation Practice Standard: Code 333. However, there is concern regarding adverse effects of excessive direct ingestion of sulfate in gypsum by ruminants. A study was established to examine the adherence and persistence of gypsum on different forage types. Bermudagrass and tall fescue were examined following gypsum applications at 0, 1, and 5 Mg ha-1 rates. The forage was sampled immediately after application, one week after application, after a 1.5 cm rain, and after a 3.3 cm rain. Substantial amounts of gypsum were observed to adhere to the forage but only persisted on the wider-leaved tall fescue. With tall fescue, gypsum adherence could be observed following a 1.5 cm rain, but not following an additional 3.3 cm rain. Results indicate that care should be observed with grazing following gypsum application, especially on wide-leaved forages, but adhering gypsum would be removed following rain.

Technical Abstract: Gypsum (calcium sulfate dihydrate, CaSO4·2H2O) has long been used to improve soils and crop production, and its use has recently been encouraged by the USDA-NRCS for soil conservation through a new Conservation Practice Standard: Code 333. However, there is concern regarding adverse effects of excessive direct ingestion of sulfate in gypsum by ruminants. As a result, the NRCS standard 333 specifies: “Do not resume grazing until rainfall or irrigation has washed gypsum off the vegetation”. However, there has been no research documenting gypsum adherence to forage or the potential for rainfall to reduce gypsum adherence. A study was established to examine the adherence and persistence of gypsum on different forage types. Two forages [bermudagrass (Cynodon dactylon L.) and tall fescue (Festuca arundinacea Schreb.)] were examined following gypsum applications at 0, 1, and 5 Mg ha-1 rates. The forage was sampled immediately after application, one week after application, after a 1.5 cm rain, and after a 3.3 cm rain. Retained gypsum was quantitated by increased Ca concentration in the plant sample. Substantial amounts of gypsum were observed to adhere to the forage but only persisted on the wider-leaved tall fescue. With tall fescue, difference in gypsum adherence could be observed following a 1.5 cm rain, but no significant difference was observed between the gypsum application and the control following an additional 3.3 cm rain. Results indicate that care should be observed with grazing following gypsum application, especially on wide-leaved forages, but adhering gypsum would be removed following rain.