Location: Agroecosystems Management ResearchTitle: Nutrient leaching when compost is part of plant growth media
|SAUER, PAT - Iowa Association Of Municipal Utilities|
Submitted to: Compost Science and Utilization
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2016
Publication Date: 3/23/2016
Citation: Logsdon, S.D., Sauer, P. 2016. Nutrient leaching when compost is part of plant growth media. Compost Science and Utilization. 24(4):238-245. doi: 10.1080/1065657X.2016.1147398.
Interpretive Summary: Bioretention cells are rain gardens that intercept water from roofs or water before it enters storm drains. They are filled with a mix of soil, sand, compost, and other materials in which plants can be grown. They are used to slow storm water flow and have a drain pipe beneath that eventually enters the storm drain system. This study showed that large amounts of compost that was partly derived from manure have a high level of nutrients that is lost in the drainage water. Layering yard waste compost on the surface resulted in less nitrate leaching than mixing the compost with sand or soil. Omitting soil from the mix resulted in subsoil densities that were too high. Mixes that had no soil lost more phosphorus. This information is of interest to urban planners and storm water consultants who develop systems to reduce nutrient loss in urban environments.
Technical Abstract: Bioretention cells collect urban runoff and are used to slow storm water surge, reduce or remove nutrients or other pollutants, and provide aesthetics to the landscape. A cell is filled with soil mixed with sand, compost, and other materials, and underlain by an aggregate layer and drainage pipe. The purpose of this study was to compare nutrient leaching and hydraulic conductivities for various bioretention cell mixtures in laboratory columns. If compost was derived partly from manure, leaching losses were too great due to the high nutrient levels in the compost. Columns containing one-third soil also lost too much nitrate; however, columns containing 10 to 15% soil and 5-10% compost that did not have manure, had lower nutrient levels in the effluent than columns with one-third soil and one-third compost containing manure. Columns that had no soil had greater phosphorus loss. Layering compost over the cell mix resulted in less nitrate leaching compared with mixing compost with the sand and/or soil, as least for the first flush loss. Adding 3% perlite mixed with biochar or 8% dolomite did not significantly affect phosphorus leaching. Layering compost over the sand-soil mix would be recommended to reduce the initial nitrate flush before plants are established.