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A study was performed to assess the use of perennial native grasses in the control of leafy spurge and Canada thistle and also to evaluate the effects of herbicides applied during the fall to leafy spurge crown buds. As part of an integrated vegetation management program, grass treatments containing the native prairie grass little bluestem established well and were effective at reducing the cover of leafy spurge. Paramount to the success of using native grass species is getting adequate grass establishment which necessitates the careful selection of grass species adapted to the specific site conditions. A fall application of the herbicide picloram at 0.5 and 1.0 lb ai/acre was very effective at controlling leafy spurge and may be mediated via the direct absorption of picloram by the elongated crown buds at this time. The report contains an extensive literature review of the biology and weed control efforts of both leafy spurge and Canada thistle.

This report presents the results of a two-year field study on the performance of erosion control products under natural and artificial rainfall conditions. Vegetation, runoff, and erosion data were collected at a newly constructed roadway. Runoff and erosion data were gathered using natural rainfall events and using a rainulator to spray water onto the surface. Treatments included a wood fiber blanket, a straw/coconut blanket, a straw blanket, a bonded fiber matrix, and disk-anchored straw mulch for natural rainfall events. For the rainulator events, a bare soil treatment also was used. Biomass, percent cover, and species composition also were measured at the research site. Five runoff events from natural rainfall were measured and revealed very little difference in sediment production between the straw, straw/coconut, and the wood fiber blankets. These blankets had approximately one-tenth the erosion that was observed for the straw-mulch plots. The impact of the erosion control treatment was substantial for early season artificial events. The sediment loading rates from the blankets and bonded fiber matrix plots were roughly one hundred times smaller than the bare soil plots and 10 times smaller than the straw mulch plots. For late season events, the erosion from these products were approximately one-half of that from straw mulch treatments.

A field-monitoring program began in the spring of 2000 to test the ability of a grassy swale at removing pollutants in stormwater. In 2001, a check dam was designed in conjunction with Minnesota Department of Transportation (Mn/Dot) engineers and installed into the vegetative swale. The check dam system incorporated some unique design features including a peat filter to trap nutrients and metals; and a low rock pool to trap water for biological processing. The check dam was designed for cost effectiveness and simple installation. The entire system was quantified and evaluated hydrologically and qualitatively both before and after the check dam installation. Pollutants monitored included total suspended solids, total phosphorus, and orthophosphorus. The average pollutant removal rates for the three storms following the installation of the check dam were 54 percent total phosphorus, 47 percent orthophosphorus, and 50 percent total suspended solids. The results suggest that properly designed short vegetative strips and swales, which include peat and rock check dams can substantially reduce pollutant levels from the stormwater exiting roadways.

The re-establishment of native plant species has been a principle objective of managers of roadside vegetation for many years. However, the establishment of native species, especially on the near inslope of roadsides has always been problematic. Soils of inslopes are generally nutrient poor, lack organic matter, and experience extreme microclimates of heat and nearly continuous drought. This report examined the concept that application of amendments to the soil or over the soil might have the capacity to increase fertility, increase soil moisture, or moderate the harsh microclimate of the inslope. In this study three different soil amendments/treatments were used to modify inslope soils including application of erosion control materials (ECMs) and enhancing soils with organic material. The two ECMs were products capable of changing soil temperatures, inhibiting soil moisture loss and/or enhancing the moisture aspect of the soil surface microclimate. The addition of organic matter is known to increase both soil water holding capacity and fertility. Although these products and treatments performed as expected, the overall conclusion of this study was that establishment of native species within two meters of the roadside was not enhanced by these treatments. Invasion by competitive weeds and weather (e.g., severe droughty conditions) appear to control the establishment of native species in the soils very near to the shoulder of roadsides.

In this project, researchers used extensive laboratory, greenhouse, and field studies to determine the relative salt tolerance of select native grasses and forbs used to re-vegetate rights-of-ways within four meters of the pavement edge. The studies found that grasses prove relatively tolerant to salt, but show poor survivability in the field during over-wintering. In contrast, forbs generally are sensitive to salt in their environment. Planting success of monocultures and mixtures of grasses near the pavement edge was poor. Observed percent coverage after two years ranged from about 10 to 20 percent over all tested species. Monitoring of longer established sites also shows that native species do not increase as a stand ages. Soil amendments including gypsum, potash, and potassium nitrate were only minimally effective in alleviating salt stress in sodic soils, although gypsum may have some promise in further field testing. The application of salt during winter salting operations also permanently and negatively impacts soil chemistry, which in concert with other plant stress factors such as soil compaction and infertile roadside soils, will continue to limit the success of establishing desirable vegetation on the inslopes of heavily salted roadways in Minnesota.

This preliminary study focused on a) surveying the concentrations of sodium and other metals along the rights-of-way of several of the most heavily traveled and salted roadways, b) development of a selection and screening method for salt tolerance in 6 species of native warm season grasses, and c) establishment of outdoor garden plots and field sites to further test the ability of native warm season grasses to grow under highly saline conditions. Salt levels along roadways were found to vary from very low to very high concentrations during the winter months but were found to decrease to levels that probably will allow germination and growth of tolerant grasses. Two species of grasses, blue grama and buffalo grass, were found to be tolerant of saline environments. Two roadside prairie restoration sites were established to further test the ability of mixtures of grasses to tolerate highly saline soils.