Erosion Control on Horseshoe Bend Hill, Idaho

After prior revegetation attempts proved disappointing, the Idaho Transportation Dept. addressed the challenge with several materials from Quattro's Quattro Advantage product line--Kiwi Power Organic Soil Treatment, Fertil-Fibers NutriMulch and Cliffhanger Tack.

Located 20 miles south of Boise, growing conditions at the sites were very unfavorable. Slope cuts range from 0.1 to 1.0 or steeper; with several huge cuts over 5,000 ft. high. Soil was decomposed granite and rock; no topsoil was present. Temperatures range from minus 0° in winter to 120° in summer. Precipitation is between 12 and 20 inches per year, usually as snow in winter.

Solution
In 1996, a six site demonstration project was funded by the Federal Highway Administration through the Idaho Transportation Department (ITD). John Steinbacher of Summit Company, hired as a consultant, recommended applying several Quattro Advantage™ materials: Kiwi Power™, Fertil-Fibers™, and Cliffhanger Tack™, along with four different blends of early seral, pioneer species seeds. The two remaining test sites were seeded and amended with a yard waste compost and composted bovine manure respectively.

The Results: The Quattro Advantage™ sites had substantially higher plant density and more sustained growth than all other attempts, at a significantly lower cost per acre - $1,055 per acre for Quattro Advantage™ versus $1,675 and $1,767 per acre for yard waste and bovine manure respectively.

Key Factors
Several factors accounted for this project's success. Each played a vital roll and could have lead to failure if not dealt with properly.

We've found that there are 8 key factors to consider on a project to ensure success:

1. Site evaluation
2. Soil testing
3. Soil microorganisms
4. Nutrient balance
5. Soil stabilization
6. Seed species selection
7. Application and monitoring
8. Moisture

1. Site Evaluation
Summit Company's assessment found several deficiencies in previous revegetation attempts. A new plan was developed to revegetate and stabilize the site.

The weather conditions, elevation, slope and directional aspect also indicated that several of the native plants could be successfully seeded.

2. Soil Analysis
The soil was evaluated for deficiencies and imbalances. It was found to be decomposed granite and rock with little to no organic matter, limited water and was low in available potassium and nitrogen.

3. Soil Microorganisms
Soil was sterile and unexposed to air or light prior to excavation. It had developed little if any micro-flora or mycorrhizae in the 9 year since. However, for any sustainable plant growth it was necessary to "jump start" the soil by stimulating the mycorrhizae fungus, which is vital to 95%of the native plants.

Mycorrhizae increases a plant's tolerance to high temperature, drought, heavy metals, salinity, toxins, acidity, pathogens and nemotodes.

Kiwi Power™ was selected as a bio-stimulant and organic soil amendment to provide soil enzymes, humic acid, cytokinins and sarsapogenin, thus stimulating mycorrhizae growth and giving the plants a much needed "boost" to establish themselves.

Application rate was 5 gallons per acre and was applied during hydroseeding.

4. Nutrient Balance
Adding elemental fertilizer was not considered, because:

1. It is detrimental to the soil organisms needed by native species and
2. The native species had been carefully selected for compatibility with the low nutrient levels

Instead, Fertil-Fibers NutriMulch™ was chosen for its high organic content, long-term release of nitrogen, potassium and phosphorous, and its high calcium content (300 lbs/ton, 5 times higher than cattle-based compost), saving both money and labor.

Application rate was 2,000 lbs. per acre and was applied during hydroseeding.

5. Soil Stabilization
Slopes were extreme and seed erosion was a particular concern. A soil stabilizer was necessary to bind seed and soil amendment to the hillside.

Cliffhanger Tack™ was selected for its UV resistance, long life and ease of use. It is an enhanced guar and bentonite clay-based tackifier with special gelling agents.

Application rate was 100 pounds per acre and was applied during hydroseeding.

6. Seed
Since the goal was to establish perennial vegetation and prevent erosion, native species known to do well at similar disturbed sites were selected from the local area. While annual grasses are often used for revegetation, they were counterproductive to our project goals and would not have survived the the extreme climate and local conditions.

Final seed mix included a combination of native bunchgrasses, blueflax, yarrow, rabbitbrush, sage and other seeds. Your project's seed mix will probably be different and should reflect the specific site conditions.

7. Application
Because of the extreme slopes, one-step hydroseeding was the obvious choice for applying the seed, organic amendments, composted mulch and soil stabilizer.

8. Moisture
Site precipitation varies between 12-20 inches per year, mostly winter snow. Spring moisture was normal, with an unusually dry May. Native plants were used because of their ability to survive this sporadic and limited moisture regime.

Conclusion
This site was extreme, both in climate and growth medium, and provided an ideal situation to demonstrate the benefits of the Quattro Advantage™ product line.

We can perform for your project - lower costs, easier application and sustained native growth - even in the harshest environments.

Each Site is Unique
Every project has its own unique properties which may influence how you design, specify and apply our products. We work with you to guarantee each project's success and minimize expense. Please feel free to contact us to discuss your particular project.

Together, we can make things grow - almost anywhere!