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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #355493
Research Project: Enhancing Production and Ecosystem Services of Horticultural and Agricultural Systems in the Southeastern United States

Location: Soil Dynamics Research

Title: Evaluation of flue gas desulfurization gypsum stability in soilless substrates under typical greenhouse irrigation practices

Author
item BROWN, B - Auburn University
item SIBLEY, J - Auburn University
item WELLS, D - Auburn University
item Torbert, Henry - Allen
item Watts, Dexter
item FOSHEE, W - Auburn University
item EAKE, D - Auburn University

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary: Gypsum has been used as an amendment to soilless substrates as a calcium source for plant growth and development, but the stability of supplemental flue gas desulfurization (FGD) gypsum has not been evaluated. A study using two soilless substrate blends commonly used in greenhouse crop production and varying rates of FGD gypsum was initiated. Dolomitic lime and a control were also included. Treatments were put into clear PVC substrate columns and leachate was collected for each treatment following normal watering for a period of sixteen days. Results show that FGD gypsum is rapidly leached from the substrate column and does not appear to be to be suitable for long-term supply of calcium and sulfur to the plants.

Technical Abstract: Gypsum has been used as an amendment to soilless substrates in many studies as a calcium source for plant growth and development. This study evaluated the stability of supplemental flue gas desulfurization (FGD) gypsum in two soilless substrate blends commonly used in greenhouse crop production: a pinebark and sand mixture and Fafard 3B. Treatments of FGD gypsum at 3.26, 6.52, 9.78, 13.0 kg • m-3, and a treatment of 3.0 kg • m-3 dolomitic lime as well as a control of 0.0 kg • m-3 were incorporated into the two soilless substrates and put into clear PVC substrate columns. Then the columns were filled with tap water to container capacity and leachate was collected for each treatment. Calcium levels were determined from leachates from each treatment using a LAQUAtwin Ca2+ handheld calcium meter. Leachate samples were gathered for a period of sixteen days. Results show that FGD gypsum is rapidly leached from the substrate column. Therefore, FGD gypsum does not appear to be to be suitable for long-term supply of calcium and sulfur and, is not likely to provide reduction of phosphorus or other nutrients in leachates from soilless substrates. Specifically, our data shows that FGD gypsum incorporated into a soilless substrate washes out of the container in very few irrigation events when a standard irrigation regimen target of 10% leaching fraction is used.