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Optimizing Grass Establishment to Stabilize Poor Soils

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Soil Erosion Research Under a Changing Climate, January 8-13, 2023, Aguadilla, Puerto Rico, USA  .(doi:10.13031/soil.23027)
Authors:   Ethan R Barnette, Charles V Privette, III, Calvin B Sawyer, Dara M Park
Keywords:   Biologic growth stimulant, Erosion, Rainfall simulator, Vegetation establishment.

Abstract

Establishing permanent perennial vegetation that is uniform and covers at least 70% percent of disturbed areas is a requirement to close-out a construction project in South Carolina. The South Carolina Department of Health and Environmental Control (SCDHEC) and the South Carolina Department of Transportation (SCDOT) have well established procedures and protocols for contractors when establishing vegetation. However, difficulties are often faced by contractors to attain these coverage thresholds, resulting in erosion and a reduction in water quality. Establishing grasses from seed is difficult, even under optimal conditions. It is believed there is a common misconception that grasses can be established from seed in a matter of only a few weeks to meet these thresholds. A two-year study was conducted at Clemson University‘s Agricultural Sciences Erosion Testing Facility to evaluate these difficulties. The study tested two different soil amendments incorporated into poor Ultisols (subsoil); topsoil and a biological growth stimulant (BGS), coupled with the use of supplemental watering on establishing vegetation. Poor Ultisols (subsoil) are commonly planted on for final stabilization in the Piedmont ecoregion of South Carolina, and often result in poor vegetative coverage. Vegetation types chosen for the study were Kentucky #31 Fescue (Festuca arundinacea) and Common Bermudagrass (Cynodon dactylon). Plantings occurred during the spring and summers of 2019 and 2020. A Standard Least Squares Regression model producing an ANOVA table, was used to analyze the final percent vegetative coverage data. For the 2019 experiments, topsoil amended plots receiving supplemental water (AMD-SW) produced the highest final coverage (66.37-88.77% for fescue and 75.88-89.55% for bermudagrass). Both 2019 tests revealed the interaction effects between the two treatments made a significant difference in the final percent coverage (p-values < 0.05). In the 2020 experiments, the BGS plots receiving supplemental water (BGS, AMND-SW) resulted in the greatest coverage for fescue (76.84%). No treatment significantly influenced cover in the 2020 fescue test (p-values > 0.05). The 2020 bermudagrass test resulted in the BGS non-supplemental watered (BGS, AMND-NSW) plots attained the highest coverage (84.93-90.47%), and a statistical relationship was determined for the non-supplemental water (NSW) treatment (p-value < 0.05). This research showed that for construction site soil conditions, it takes more than six weeks to reach this 70% coverage requirement. Most of the experiments did not reach the 70% threshold until the eighth week of growth. Future research should be conducted on methods to reduce the timeframe required to reach the 70% uniform coverage threshold. One limitation of this research was that it was conducted primarily on soil types common for Upstate South Carolina.

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