Construction in urban zones compacts the soil, which hinders root growth and infiltration and may increase erosion and degrade water quality. The purpose of our study was to determine whether planting prairie grasses and adding compost to urban soils should partially mitigate these concerns. We simulated construction activities by removing the topsoil, and compacting the soil by repeatedly driving over it with a tractor. Additionally, treatments included three compost application methods (compost and aeration, rototill and compost, surface compost). Plots were subjected to simulated rainfall applied using overhead sprinklers at a rate of 65 or 72 mm•h ) compared to plots planted with bluegrass (Poa pratensis L.). A 5 to 7.5 cm thick compost blanket reduced time to runoff (60 min) compared to no compost addition (9 min). Topsoil addition without compost did not develop dark surface soil. Compost additions are recommended to reduce negative effects of urban compaction. Over time, the depth of compost additions decreased, necessitating further additions.

Engineered plant growth media must support plant growth while minimizing environmental impact. The objective of this research was to determine how different growth media influence nutrient leaching. Plant growth media contained varied amounts of soil, sand, compost that did or did not contain manure, and possible sorbents for phosphorus. If the plant growth media included compost derived partly from manure, leaching losses of nutrients were excessive due to the high nutrient load in the compost. Layering compost over the plant media mix resulted in lower nitrate concentrations in effluent (87 mg L ¡1 ) compared with mixing compost into the media (343 mg L ¡1 ); however, growth of prairie grasses was reduced because of dense media below the compost blanket (0.09 versus 0.31 g). Using lower amounts of compost that did not contain manure resulted in lower mean nitrate concentrations in effluent (101 versus 468 mg L ¡1 ). Media that had no soil (13.3 mg L ¡1 ) had greater loss of phosphorus after harvest for unsaturated drainage than media with soil (1.8 mg L ¡1 ). To reduce nitrate leaching, only small amounts of low-nutrient compost (higher C:N ratio) should be incorporated into the media. If compost is applied as a surface blanket without incorporation, then soil should be added to the sand to reduce density of the media and increase plant growth.

Engineered soil mixes are expected to maintain plant growth while minimizing nutrient leaching in greenhouse and bioretention applications. Iron (Fe) has been suggested within plant growth mixtures as a sorbent for phosphorus. The purpose of this study was to determine if Fe filings are an appropriate component of engineered plant growth mixtures. Iron filings were added to engineered soil mixes in laboratory columns, and plants were grown for 2 mo. Unfortunately, Fe filings partially cemented the engineered mixes, especially the treatment with sand and compost but no soil. After completing the study, orange and red aggregates were apparent. Although Fe filings might be useful in filter beds, they were not suitable within engineered plant growth mixes.Core Ideas Iron added to sand mix resulted in partial cementation. New red and orange aggregates were formed in the sand mix. Iron should not be added to soil mixes where plants will be grown.

Construction removes soil from one site to another site. The aim of this study was to compare soil carbon of fill material and buried soil. The fill had topsoil and subsoil layers over a buried soil. The buried soil had significantly higher organic carbon (22.7 g kg −1) than the fill had (12.4 g kg −1).