Author
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SAUER, PATRICIA - Iowa Association Of Municipal Utilities |
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Logsdon, Sally |
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Submitted to: International Erosion Control Association Proceedings
Publication Type: Proceedings Publication Acceptance Date: 2/13/2013 Publication Date: 4/15/2013 Citation: Sauer, P., Logsdon, S.D. 2013. Go native: blue gamma-buffalo grass and compost benefits urban soil. International Erosion Control Association Proceedings. Available: http://ieca.crhosts.com/file.php/183/Sauer.pdf. Interpretive Summary: Urban construction sites often have excessive erosion and compaction after topsoil removal, scraping, and grading. Soil was improved by mixing compost with the topsoil to six inch depth, and planting buffalo grass and blue gamma grass. Compared with the lawn control treatment, the improved site had better water holding capacity, eliminated sediment loss, and had more roots penetrating the dense subsoil; however, runoff was not reduced. Native prairie grasses and compost benefit highly disturbed urban soils. This information is useful to urban planners and to anyone who wants to build and maintain a healthy lawn. Technical Abstract: Urban construction sites often have excessive erosion and compaction after topsoil removal, scraping, and grading. Restoring the hydrologic function of soils can reduce runoff and provide a useful tool for post construction stormwater management as it has very few site limitations. The purpose of this study is to determine if compaction remediation efforts are effective on a simulated urban site. Studies were conducted on research plots in Ankeny, Iowa. In the first part of this plot study, sod and topsoil were removed, the area was graded to a 1% slope, and the subsoil was compacted by trafficking. The untreated topsoil was re-applied to the control area about 5 cm deep, and a compost: topsoil mixture (2:1) was surface applied to the improved area to a 15 cm depth. A Bluegrass lawn mixture was planted to the control side. Buffalo grass (Buchloe dactyloides) and blue gramma grass (Bouteloua gracilis) that are short, turf-forming, native Midwestern grasses were planted on the treatment side. Soil water content was measured at ten spots for each treatment. Bulk density was monitored at several locations within each plot. Rainfall simulation was used to evaluate infiltration, runoff, and sediment loss. After three years, blocks of soils were sampled to examine roots and soil structure. Additional small trial plots compared the following treatments after topsoil removal and grading: compaction; control with only topsoil added; topsoil, plug aeration, then compost blanket; rototilled to incorporate topsoil and compost; and compost blanket. Plots were planted with a bluegrass mixture. Bulk density was monitored at several locations in each plot. Plots will be monitored for runoff using rainfall simulation during the 2012 growing season. In addition organic carbon content will be monitored from cores collected from each plot. Results from the first study indicate that the native grasses formed a dense stand of turf similar to the control turf grass area. The improved area held more water than the control area. Runoff was greater for the improved area than the control area, but sediment loss was reduced. In both control and improved areas, roots penetrated into the dense subsoil around clods or structural units, but the improved area with native grasses showed more roots penetrating into the subsoil. Preliminary results from the small plots from the second part of the study show reduced bulk density compared with the control, but there was no significant difference among the compost treatments. None of the treatments alleviated deeper subsoil compaction. Native prairie grasses can benefit compacted highly disturbed urban soils as well as compost, and tillage to help restore the hydrologic function of compacted surface urban soils. |
