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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #311234
Title: Iron filings cement engineered soil mix

Author
item Logsdon, Sally
item SAUER, PAT - Iowa Association Of Municipal Utilities

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2016
Publication Date: 7/11/2016
Publication URL: https://handle.nal.usda.gov/10113/6637061
Citation: Logsdon, S.D., Sauer, P.A. 2016. Iron filings cement engineered soil mix. Agronomy Journal. 108:1753-1757. doi: 10.2134/agronj2015.0427.

Interpretive Summary: Bioretention cells are like rain gardens that collect runoff before it enters storm drains. The bioretention cells are filled with mixtures of sand, soil, compost, and other filter materials to reduce water and chemical loss to storm drains. Plants are grown in the bioretention cells for aesthetics and to take up nutrients. This study showed that iron filings were not an appropriate filter material mixed into bioretention cells. The iron was transported by the water and leached out the drain, taking phosphorus with it. The iron made the soil mix hard and cemented and did not help plant growth. This study is of importance to scientists interested in how iron interacts with soil nutrients, and for urban planners who design the mix for bioretention cells.

Technical Abstract: Bioretention cells are used in urban stormwater management to reduce storm surge and nutrient loss. The cells are filled with mixtures of soil, sand, compost, and other materials, and are underlain by a drain. The purpose of this study was to determine if iron filings would be a suitable filter for phosphorus in bioretention cell mixtures. Iron filings were added 3% by volume to sand-loess soils-compost mixtures in laboratory columns. Other treatments included sand-compost mixtures with iron filings and a 100% compost mixture. Effluent was very dark from several of the treatments, and the darker effluent had less nitrate but more total phosphorus. Some of the columns still had dark effluent after growing plants. The iron apparently contributed to redox reactions with the nitrate, either in the column or in the effluent. The iron may have bound with organic matter (from the compost) and phosphorus, which could have contributed to increased phosphorus leaching. After harvesting the plants, the soil mix in the columns was somewhat cemented. Iron filings are not recommended within the bioretention cell mix, but could perhaps be used in a filter sock that filters effluent from the bioretention cell.