Details:

Creators:
Brown, Rebecca Nelson ; Gorres, Joseph ; Sawyer, Carl
Brown, Rebecca Nelson ; Gorres, Joseph ; Sawyer, Carl Less -
Corporate Creators:
University of Rhode Island
Subject/TRT Terms:
[+]
Deicing Chemicals Environmental Impacts Grasses Grasses--Effect Of Salt On--Rhode Island Grasses--Rhode Island Roadside Flora And Fauna Sodium Chloride Soils
Publication/ Report Number:
FHWA-RIDOT-RTD-07-2A
Resource Type:
Tech Report
Geographical Coverage:
Rhode Island
Edition:
Final; 2007-2010.
Corporate Publisher:
Rhode Island. Dept. of Transportation
Abstract:
Roadsides in Rhode Island and elsewhere are planted to mowed turfgrass in order to prevent erosion, improve aesthetics,

maintain visibility, and provide a safe means of stopping errant vehicles. However, there are a number of ways in which

mowed turfgrass is failing to meet the expectations of highway managers and the traveling public. Regular mowing and turf

maintenance is expensive. Use of non-native plants has resulted in problems with invasive species. Most importantly, the

seeded turfgrasses are not surviving in the roadside environment and so are failing to prevent erosion.

Solving this problem requires answering two questions: why are the seeded turfgrasses dying? And how can this be fixed

given severe limitations on funding? The purpose of this study was to seek answers to the first question, and then generate

possible solutions to the second. The initial hypothesis was that high levels of deicing salt were responsible for the damage.

We proposed to test this hypothesis by establishing test plots of 21 grass varieties selected for tolerance to salt in the highsalt

zone at two locations: I-95 North in Hopkinton, and I-295 North in Lincoln. The grass variety trial was combined with a

test of two potential low-cost soil amendments: yard waste compost and biosolids. We also proposed to monitor salt

deposition over two winters at six sites to determine how much salt the grass was being exposed to, and how long the salt

persisted in the root zone. Persistence is important because the grass is more sensitive to salt damage when it is actively

growing (April-October) than during the winter months. At the same time we proposed to survey the vegetation on

established, mowed roadsides to determine which plant species were surviving, as these might be good candidates for

inclusion in a modified seed mix.

We found that salt tolerant grasses showed no improvement in survival over the grass varieties already in use, even though

the salt tolerant grasses had shown significantly better survival in greenhouse salt screening trials. This suggested that the

salt was not the primary cause of vegetation failure; the finding that the salt did not persist in the root zone at levels high

enough to cause plant damage past early April further supported this hypothesis. Soil amendment, however, had a dramatic

effect on turfgrass survival. Perennial vegetation cover on plots amended with biosolids remained above 50% throughout the

two-year study, and beyond.

At the beginning of this study it was assumed that most of the vegetation surviving on mowed roadsides was the turfgrasses

seeded by RIDOT or weeds such as quack grass, sheep sorrel, and crab grass. However, in surveys of seven sites in mowed

areas along limited access highways in Rhode Island we found a total of 80 plant species, approximately half of which are

native to Rhode Island.. Our results suggest that the seed mix used by RIDOT is not persisting on the roadside, but that it is

gradually being replaced by native or naturalized species. Reductions in mowing would further this process, as they would

permit more of these naturally-occurring plants to mature seed, filling in gaps created by vehicles and other disturbances.


Format:
PDF
Funding:
SPR-231-2299
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:15c2ce070c3a0604bfc4c8f1ba8e8fa4e599fddd72efe41ed6ebab3ccdd6b8f6
Download URL:
https://rosap.ntl.bts.gov/view/dot/23797/dot_23797_DS1.pdf
File Type:

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