Erosion Control Performance of Crimped Straw Mulch on Simulated Highway Roadsides

Increasing demand for effective roadside revegetation has compelled numerous studies on proprietary and non-proprietary erosion control materials and practices. These findings contribute significantly to the Texas Department of Transportation’s (TxDOT) Approved Product List (APL), which catalogs commercial products exceeding TxDOT’s minimum performance standards determined by product performance testing. The objective of this study was to evaluate the often overlooked crimped straw mulch on its erosion control performance of (1) sediment loss and (2) vegetation establishment on the simulated highway environment. This study is part of a long-term research goal to expand the coverage of the current APL to include non-proprietary erosion control best management practices. In this study, tests were conducted using artificial rainfall simulators on two large-scale slopes (2:1 and 3:1) in 2005-2006. Test conditions covered two soil types (clay and sand) and four straw weight applications (2.24, 4.49, 6.73, and 8.98 metric tons/ha). The vegetation density was tested on small greenhouse trays placed on a 2:1 and a 3:1 rack. Percent coverage by live grass on each tray was measured to determine vegetation density. The results concluded that sediment loss decreases with increasing weight of crimped straw mulch. On 3:1 slopes, all rates of the crimped straw mulch could protect the soil surface either equal to or better than the proprietary products approved by TxDOT. For slopes of 2:1, heavier applications of crimped straw mulch are needed to reach the protection level a TxDOT-approved product can provide. Vegetation density testing yielded inconsistent results with no clear trend, which is likely due to the small test trays, the lack of replications, and insufficient time for vegetation establishment.