Landscape Architect Articles

LCN September 2007 Focus Feature08-30-07 | News

Hydro Mixture Basics

The Hyde Park golf course in Cincinnati, OH is being hydroseeded with a Finn hydroseeder. Finn and other companies educate landscape contractors how to best utilize their hydroseeding equipment and new consumables.

Hydroseeding is a growing industry for contractors and the numerous benefits include a speedy process, the ability to cover hard to reach places, faster growth, and increased plant success. The basic materials are water, seed, fertilizer, and mulch. Tackifiers are mixed with mulch in soil erosion cases.

Water

Water is the mixture?EUR??,,????'???s carrier and also provides soil moisture. In dry and compacted soil, a contractor might spray water over the ground beforehand.

Seed

The type of seed to use varies by the area and the client?EUR??,,????'???s desires, and is often specified by government contracts or district, depending on the type of soil and climate. It is usually a mix of several different grasses and can vary from lawn seeds to native seeds with wildflowers added. More and more requests are being made for native seed, as it may require less fertilizer and be more drought resilient.

One example of a type of state-specified grass mix is the ?EUR??,,????'??foothills mix,?EUR??,,????'?? which is used for many new developments in the quickly growing parts of Fort Collins, Colo. This cost-effective mix consists of native grasses, such as wheat grass, grama, rye grass, and hard fescue.

The seed mix also might depend on the type of year, as in each season amendments might be added to produce quicker root growth such as Bermuda grass in April or May and German millet in the summer. The seed mix might also be mixed with fertilizer, and occasionally lime might be necessary to lower the acidity of the soil.

It is best to know the climate, test what works, and to use a hydromixture with several types of seed to ensure that at least the best one will win out.

Before

Fertilizers

Fertilizers, often those with a high phosphorus content, may be added to the seed slurry to enhance root growth. Fertilizers also work on a site-by-site basis and also depend on the soil and the time of the year. The state also specifies the type of mixture to be used. For example, most Alaska highway projects specify a 20-20-10 granular-type fertilizer. This is used in native soils with most seed mixes. There is a trend in using organic fertilizers in the mix.

Mulch

Mulch is usually sprayed after the seed flurry and helps protect the seed and seals in moisture. Either paper or wood or a mixture of the two can be used. The Texas Transportation institute recommends mulch made from recycled newsprint or a 70/30% paper/wood mix called Enviro-Mix. Mulch rates can be anywhere from 1,500 pounds per acre to 2,500 lb./ac. depending on the thickness of the mulch as well as the type of terrain. A dye is often added for aesthetic purposes and to indicate what has been covered.

After Application

Tackifiers

Tackifiers may be added to the mulch to anchor the mixture to slopes and help seal in moisture. They are a common addition in erosion control situations. One example of a ratio includes an 80/20% paper / wood mulch and tackifier. Many are guar gum?EUR??,,????'??+based, such as Canfor?EUR??,,????'???s EcoFibre tackifier, or a guar gum / polyacrylamide combination. One advantage of using the polyacrylamide is the decrease of water turbidity in runoff. It also cleans the water. Using a tackifier also makes a slicker slurry making it easier to clean the machine afterward.

Soil Amendments

Several advancements have been made in biostimulants, soil amendments, and microbial products. StikPlus, a Finn product, is a tackifier with fiberglass fibers to increase its holding power. In dry areas, polymer compounds, such as HydroGel, are helpful. These hold up to 500 times its weight in water and maintain a steady release. Finn HST contains humic acid, which holds the nutrients in the soil instead of allowing them to leach out quickly. This is especially helpful for clay soil.

Some soil amendments are used to improve soil?EUR??,,????'???s pH. Bonded fiber matrix (BFM) materials are great for areas that have to withstand high stress on steep slopes, but require certain amounts of water.

Biostimulants are plant hormones and bacteria that cause the seed to sprout faster and grow stronger. Soil disturbed by construction may lose microbes that were present. For many large projects and highway construction zones, the addition of microbial bacteria is a good idea to increase the chances of success. New research is leading to a wider variety of biostimulants, such as Finn?EUR??,,????'???s HydroMax blend.