United States Department of Transportation
i
Madison County energy conservation study : 2012-2013 survey of roadside vegetation.
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2014-02-01
[PDF-10.55 MB]
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Abstract:The current clear zone mowing frequency for I-10 in Madison County (FDOT Maintenance District 2) is 7 times per year. To conserve energy and reduce expenses associated with mowing, a pilot study was implemented in 2009, and continued in 2010-11 (Contract No. PR4170440) and 2012-13 (current contract). In cooperation with District 2 maintenance personnel, mowing of the westernmost mile of I-10 in Madison County was limited to a 10- to 15-ft safety strip along the edge of pavement until the time of the fall cleanup mowing. As was done from 2009 to 2011, vegetation surveys of the clear zone were conducted by walking forays twice per year – spring (March) before the first safety strip mowing and fall (October) just before the cleanup mowing. The main objectives were 1. Document the presence and approximate extent of (a) desirable and showy native wildflower and grass species, and (b) nonnative species, especially those listed as undesirable by FDOT Maintenance Rating Program (MRP) standards, and 2. Suggest management practices for the predominant species in the clear zone. In addition, soil characteristics were recorded in fall 2012 and 2013 where Bidens alba (Spanish Needles) was abundant. This species is of special concern because FDOT anecdotal evidence suggests that it causes erosion. However, no erosion has been noted in the pilot study, even where Bidens alba was dense. The relationship between this species and erosion may be due to soil characteristics. The modified mowing regime has not and is not expected to interfere with normal highway operation in the near future. The widespread occurrence of the MRP undesirable species Ambrosia artemisiifolia (Common Ragweed), Bidens alba, Eupatorium capillifolium (Dogfennel), and Paspalum urvillei (Vaseygrass) has not resulted in any erosion, or sites likely to erode. Moreover, in locations where non-turfgrass species may be outcompeting traditional turfgrass species, the non-turfgrass species appeared to have provided the same soil stabilization functions of traditional turfgrass species. It was also clear that under the environmental conditions of this study bahiagrass and Bidens alba can co-exist, and at least to the degree that erosion does not occur even in an alkaline, sandy type soil. Further research is needed to determine if the degree of sandiness and/or other factors are resulting in erosion observed on FDOT roadsides in other parts of the state. Other significant outcomes of the 4-year modified mowing regime were: 1. Improved safety to motorists because of the reduced presence of mowers and string trimmer operators, 2. Reduced mowing costs, 3. Increased diversity – the number of species in the safety strip clearly was less than in the remainder of the clear zone; and 4. Improved aesthetics – the apparent density of spring wildflowers increased, especially the showy Tradescantia ohiensis (Spiderwort) and Salvia lyrata (Lyreleaf Sage). In conclusion, this pilot study clearly provides evidence that mowing costs can be reduced and energy conserved without negatively impacting normal highway operation. The best locations to implement reduced mowing strategies are rural areas where motorists appear to accept a less manicured turf.
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