Revegetation of a site involves a variety of factors. Seed, soil amendments, and soil stabilization products must all work together to fulfill the design plan. Choosing the right ingredients is a challenge for any erosion control specialist. Getting a good stand of grass quickly is great, but not if the plants soon wither and die or have to be constantly watered. The best erosion control is the establishment of plants, but they must be viable for season after season. Factors to consider:
- Seed needs– Is native seed required? Does the project demand a fast-growing or temporary seed, or a permanent mix? What are the elevation and expected rainfall amounts?
- Soil conditions– The type of soil will determine what other enhancements, such as fertilizers and other amendments, might be required.
- Topography– What are the slopes, and how will they be graded and prepared?
- Time of planting– Depending on the growing season, different seed mixes and fertilizers may be used.
- Availability of irrigation– If seed germination will receive moisture only from rainfall, a different seed and planting method might be called for.
- Cost– Of course, cost of seed, amendments, and labor is always a vital factor of any project.
You will need to consider carefully the soil, the seed, and the soil amendments.
Soil, Earth, or Dirt
It doesn’t matter if you call it soil, earth, or dirt-this is the foundation of your project. Its condition must be considered foremost. The type of soil-clay, loam, or sand-is important. But the condition of the unseen world is also crucial.
Soil that has been disturbed by construction activities or packed down by equipment traffic has lost much of its character. Microbes that live in the soil and support plant life can be destroyed in these conditions. Testing to determine the extent of microbial density is important to what steps need to be taken to revive the soil.
Seed the Best
One of the prime considerations for a revegetation project is the kind and quality of seed. Many times, contractors are required to have visible growth within 30 days. A planner might specify a fast-growing, short-living plant for quick erosion control along with a slower-growing, permanent plant. The combination will provide vegetation establishment in a short window with other plants for the long term.Seed quality is critical. If you plant a weak seed or a mixture that is contaminated with weed seed, your problems multiply, literally. Premier companies, such as S&S Seeds of Carpinteria, CA, Granite Seed Co. of Lehi, UT, and Justin Seed Co. of Justin, TX, offer quality PLS (pure live seed) that is weed free. The companies also provide ideas for seed mixes, including natives for your area.
Nutrient Cycling
One of the most critical parts of revegetation projects is making sure the new plants will thrive. Tom Bowman, division president of Rocky Mountain Bio Products in Denver, CO, is adamant about the importance of a good soil amendment plan. He doesn’t like the word “sustainability” in this sense because, while that’s a good start, it does not mean that the soil and plants are healthier than they were at the start of the project. Fertilizer is still required, and, over time, even though it may take several years, plants will wither away because the soils are depleted.The better term is what Bowman calls “nutrient cycling.” If plants and soils are healthy and feeding each other, two positive results occur. First, the nutrients are always there. Second, the native plants will reseed themselves.Fertilizers and amendments from Rocky Mountain Bio Products help a site achieve nutrient cycling. Biosol Natural Organic Fertilizer is similar to a slow-release vitamin for people. It promotes a mix of microbes providing nutrients for the plant to absorb through its roots. The organic material in this fertilizer will not burn plants and does not have to be watered in. Biosol is part of the USDA Biopreferred program, which provides a list of environmentally friendly products.Mycorrhizal inoculations provide beneficial fungi that strengthen plants against disease and stress, improve water and nutrient uptake, and enhance plant and root growth. Applications available from Mycorrhizal Applications and supplied by Rocky Mountain Bio Products include powders and granules.Earthgreen Menefee Humate All Natural Organic Soil Conditioner provides humic acid and carbon compounds to improve the soil. Use of Humate makes nutrients more available for the plants and improves soil structure so that it turns from a poor soil into one ready to enrich plant life.When these three products are used, Bowman says, food sources are provided for plants, fungi, and bacteria, leading to nutrient cycling that will continue to provide good soil and healthy plants.Here are the details from some projects that might help you with your next task.
Colorado Applications
Curtis Bollig, project manager for Seco Erosion Control in Aurora, CO, recently completed a revegetation project for the city of Aurora. The Marina Tank and Pump Stations contract consisted of revegetation after construction of pipelines and pump stations from the Aurora Reservoir. The soil was fairly hard and had been recently graded after the construction was finished. Products from Rocky Mountain Bio Products and native seed were specified for the project. The first phase-revegetation of a long section of pipeline-was completed in May 2009 and the second phase in September 2009. Biosol Natural Organic Fertilizer was applied with Earthgreen Humate and straw mulch, using a blower machine. Mycorrhizal mixture and seed were drilled in. Germination occurred in about two weeks, and within two months there was a good stand of grass about a foot tall; Bollig estimates 70% to 80% coverage. He says the project went smoothly. He likes the products and will use them on other contracts.California Contract
Hanford ARC of Sonoma, CA, has participated in a long-term restoration project along the Napa River. The first part of the project included breeching levees to flood wetlands and restoring plants to those areas. About 56 acres were drill-seeded with native seed and wetland plants. Challenges were that the neighboring land was weedy grassland and that Canada geese damaged the plants. Solutions included mowing, hand weeding, and herbicide application to attack the weeds. Wetland plants were placed in groups and protected from the geese. After three years, the plants are thriving and the wetlands have been reestablished.Another portion of the contract involved erosion control measures and seeding along the Napa River. The floodplain areas were hydroseeded with native seed, mycorrhizal fungi, and compost.Tahoe
Restoration
The Griff Creek Stream Environment Zone Watershed Restoration Project involved removing a dam and restoring streambanks and the reservoir. The stream leads into Lake Tahoe, so sediment control was essential.The dam and its surrounding area were excavated and graded. Geotextiles were placed for sediment control.Revegetation of the site included planting native seed mixes. Soil amendments and mulch, some of it clean pine needles collected onsite, were applied. Container plants-willows and conifers-were installed. The slopes were stabilized with willow wattles. With adequate watering, the area was prepared for winter dormancy.
Texas Pipelines and Drilling Sites
When oil companies install pipelines or build drilling sites on ranchland, owners want the property returned to good grazing land. Bo Hughes of Hughes and Foster, based in Benbrook, TX, has supervised many of these projects. “It’s very important to have everything be safe for cattle or wildlife,” he notes.Anything that is planted on rangeland must be good pasture for cattle. It must match or improve on the available pasture. For those seeds, Hughes depends on Justin Seeds. The company also is helpful with soil samples for all kinds of projects. For commercial and residential project, the seed used is often Bermuda. Depending on the temperature, Bermuda will germinate in 48 hours and show a heavy stand in 10 to 14 days with regular watering. For projects carried out in cooler weather, Hughes uses a mixture of winter grasses until it is warm enough to add Bermuda.For many projects, Hughes hydromulches a mixture of seed, fertilizer, and Soil Guard. Soil Guard holds mulch and seed in place, is not hazardous to cattle or wildlife, and adheres to the soil, but allows moisture and sunlight to penetrate.Hughes notes that it is difficult to grow grass in the clay and rocky soil often found in north central Texas. Applications of fertilizer and other soil amendments can help. “The sooner you can get grass growing, the better erosion control and aesthetics you get,” he says.One commercial property on which he worked featured a steep embankment by a parking lot. Hughes smoothed the embankment and dug a drainage area for stormwater runoff. He hydromulched Soil Guard and a mixture of Bermuda, winter grass, and native seed with fertilizer and mulch.Forty-eight hours later, a heavy rainstorm of 3 to 4 inches occurred. The site held up with no mud released from the site, even though the vegetation had no time to establish.
Delaware Projects
Charlie Ewing, construction supervisor for Curbs Inc. in Smyrna, DE, says his company handles quite a lot of landfill, golf course, and highway work. For vegetation, he uses products from EarthChem of Fort Collins, CO. The state of Delaware specifies native seed, so Ewing mixes EarthBound Soil Stabilizer and Mulch Tackifier, wood mulch, seed, and fertilizer. The mixture is applied to what Ewing calls “pretty good soil” on most of the projects. Irrigation is not needed because the area receives adequate rainfall. The seed applied is usually a hard fescue because it is a low-maintenance plant.In describing EarthBound, Kevin Loucks, owner of Earth Chem, says that its primary function is as a soil stabilizer. The product doesn’t allow the soil to break down into a crust and keeps it from flowing away from the site. It is a flocculant that is designed to separate or keep separate liquids and solids, allowing water to penetrate soil and make it available for plant roots as well as preventing sediment runoff. A study by the Texas Department of Transportation showed that clay soils treated with EarthBound prevented sediment runoff by 74% to 85%, even on steep slopes. Sandy soils saw sediment reduction of 57% to 63%. Vegetation growth was enhanced by 73% to 81%.
Promoting Microbes
Reforestation Technologies International of Salinas, CA, supplies mycorrhizal fungi to seed companies, landscaping companies, the US Forest Service, and other clients. Neil Anderson of RTI says that heavily disturbed land loses beneficial microbes such as mycorrhizal fungi. The destruction of the microbes leaves dead soil that cannot support plant life. It’s often very difficult to seed such a site and get a lasting stand of plants without large amounts of fertilizer and frequent reseeding. Restoring the microbe environment creates a nutrient-rich soil that is ready to support a vibrant plant community.Anderson says that projects such as areas of exploration for oil and gas, construction sites, or any site that has had heavy equipment traffic has probably suffered loss of microbes. Weeds move into the poor soil that remains. Revegetation must establish healthy soil and plants to retard the growth of weeds.A project along the Carson City Freeway in Nevada included large cuts and fills with cheatgrass in the vicinity. The area was replanted with RTI’s mycorrhizal fungi application and seed. The slopes were track-walked with a Caterpillar before being hydroseeded. The seed quickly rooted and grew, and the site is free of the large stands of cheatgrass common on disturbed sites in the Great Basin.
A dry lakebed near Carlsbad, NM, demonstrates the efficacy of mycorrhizal fungi application. The land had been inundated by the lake for 100 years and then dry since the lake was drained in 1991. The soil was void of any microbes. The noxious plants of salt cedar and kochia had spread throughout the site. The first step of the revegetation plan was herbicide application to kill the weeds. The area was disked, and then the seed and mycorrhizal mixture were incorporated by imprinting or roller chopping. Mycorrhizal inoculation improved the plant density by about three times. The fungi improved the viability of the plants enough to support the seed that was planted, even in the dense clay soils.
Missouri Lead
Kevin Pollock, owner of Pollock Landscaping, Ironton, MO, has used some of the techniques described above to revegetate an area of EPA Superfund projects. Residential soils in two Missouri counties were found to be contaminated with lead. In Washington County, the lead was naturally occurring, but in Jefferson County the lead came from backfill hauled in after construction. The contaminated soil was removed down to depths ranging from 6 inches to 2 feet, and replacement topsoil was hauled in. Pollock’s task was to prepare and seed the new lawns. The project has covered more than 400 properties, or about 150 total acres.Pollock power-rakes and finishes the grade for each yard. He hydroseeds the area with 100% wood mulch at 2,000 pounds per acre, then adds fertilizer and a mixture of annual rye and fine fescue known as K31. The K31 is easy to grow and hardy, especially to drought and traffic. He has used a fine fescue exclusively. But the biggest problem on the project was that homeowners were not consistent in watering, so the grass suffered from drought conditions. However, the K31 can survive even with inconsistent irrigation. If needed, he adds lime to adjust the pH to help establish the grass.Pollock uses two Finn HydroSeeders to apply the mixture; a T75 and a T120. He calls the Finns the Cadillacs of the hydroseeding world and says they make his job much easier: “They’re great machines.”The main challenge with these seeding projects has been the amount of initial irrigation by the homeowners.Pollock has a printed watering sheet that is given to each homeowner, explaining that the area needs extra water for the first couple of weeks. He advises short periods of frequent of watering, then lengthening irrigation times and spacing them out further.The sheet includes symptoms of under- or overwatering and informs homeowners that a good lawn can take a couple of years to be established. Pollock adds examples of real life properties as illustrations.
Tennessee Mine
A former copper mine site in southeastern Tennessee provided a plethora of challenges for revegetation. Since the mid-1800s, the Copper Basin had been the site of copper mines and mills. The London Mill area underwent reclamation in a plan developed by Glenn springs Holdings Inc., a subsidiary of Occidental Petroleum Co. The extensive project started in 2001 and is reaching completion.For the revegetation part of the project, contaminated soil was removed, leaving little topsoil. The remaining soil had a low pH of about 4.5 and little organic content.The area was graded and contoured, and lime was added to adjust the pH. The seedbed was disked, and fertilizer and seed mixtures were applied. For the fall season, a mixture of rye grains, fescue, gramma, clover, and other native seeds were planted.In spring, annual rye grass and native seeds were the choices. If the section was planted during hot weather, Bermuda grass was added to the mix.In spite of the daunting challenges, the site is stabilized and vegetation is well established.
Denver Bikes
American Civil Constructors of Littleton, CO, completed a project that had to wait through the winter to germinate and grow. According to Chad Anema, project manager, a concrete bike path, the Cherry Creek Trail, was constructed from the Cherry Creek Reservoir to downtown Denver. Part of the trail runs along Cherry Creek, so runoff of pollutants was a concern.The soil is sandy, so erosion control measures were critical. Biosol Natural Organic Fertilizer was applied rather than compost. A mixture of the fertilizer, straw, and tackifier was hydromulched. Some sections were covered with erosion control blankets. The seed, a mixture of native seeds specified by the city and county of Denver, was drilled in. The project was finished in mid-October 2009, so the erosion control measures had to hold through the winter months and provide stability for seed germination in the spring.
Carolina Landfill
After reaching capacity, the Sumter County Landfill was closed and needed reclamation. The site is located about 30 miles from Columbia, SC. To build a sustainable plant community, the environment would have to be created from scratch.Six inches of fill were trucked in and compacted, then 6 more inches of topsoil installed. The soil pH and organic content were too low, so amendments were needed. Representatives from Pennington Seed in Madison, GA, and from Profile Products in Buffalo Grove, IL, presented a plan to overcome these obstacles.Profile Products NeutraLime Dry was applied at a rate of 160 pounds per acre to raise the soil pH. The granular application raises the pH in three to seven days. A second product, JumpStart, was applied at a rate of 5 gallons per acre. This substance improves moisture retention and enhances root development. A slow-release fertilizer, BioPrime, was added to provide nitrogen. Total Gro 15-30-15 water-soluble fertilizer was also introduced, along with mycorrihzal fungi.The seed mixture supplied by Pennington was a specially formulated Slopemaster mix of Bermuda, browntop millet, weeping love, annual ryegrass, hairy vetch, and durana clover applied at 100 pounds per acre. The total application was covered with Profile’s SoilCover Wood with Tack hydraulic mulch, applied at 1,500 pounds per acre. In spite of hot June weather, the seed showed germination and establishment in a couple of weeks. By the end of July, the site was revegetated and showing great growth.
