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Sod

General

Sod stabilizes disturbed areas with dense, permanent vegetative cover immediately after it is installed. Dense, established vegetation protects the soil from raindrop impact, reduces flow velocities, increases infiltration and reduces soil loss from the site and is the most effective immediate site stabilization practice available.

Sod is applicable on any area of the site on which final grading has been performed. Most often, sod is applied to critical areas where immediate vegetation is required or on areas where seed establishment is difficult, such as in channels or on steeper slopes. It is also used as an alternative to seeding in residential and commercial applications and on golf courses and other areas where aesthetics are important.

Vegetation

Sod, if properly maintained, provides dense vegetative cover throughout its life. However, if the sod is not properly cared for, the vegetation will die and the practice will be rendered ineffective. As a result, only densely established vegetation should be relied upon to provide erosion control.

The species of vegetation selected will vary greatly depending upon the characteristics of the site and the long-term maintenance requirements of the species. Soil type, pH, slope, site use, maintenance, growth rate, and the time of year it is planted are all factors that must be weighed when selecting sod. In addition, sod that is to be applied in channels should be capable of withstanding the designed flow velocity for the channel. Only healthy, high quality sod that is free of exotic or invasive species, disease, and insect problems should be selected for use.

Sod should be harvested uniformly under proper conditions. Cutting during extremely wet or dry weather may result in the failure of the practice and require re-application.

To promote the success and viability of the practice, sod should be harvested no more than 36 hours before it is installed on site.

Surface Preparation

To be successful, sod requires a properly prepared surface. Areas with poorly drained soils may require that amendments be made before sod is installed.

Topsoil should be loose, uniform, well pulverized, and available in sufficient quantities to promote rapid growth. Compacted soils should be loosened to a depth of at least 6-8 inches by using a chisel plow or similar implement to ensure adequate pore space. If less than 3-4 inches of topsoil are present on site, additional soil may be required.

Soils should be tested for nutrient content and pH to determine the amount, if any, of fertilizer or lime required. Over-application of these soil amendments is costly, ineffective, and may cause serious pollution problems. As a result, lime and slow releasing fertilizers should be applied only as needed and should be incorporated into the soil to keep them on site and in the root zone.

The organic content of the soil is also an important consideration when preparing the surface. Soils rich in organic matter possess high levels of nutrients and microorganisms, which improve the growth rate, require less fertilizer to be applied, and increase the porosity of the soils. To improve the organic content of the soil, organic compost may be incorporated into the top ten inches of soil.

To ensure adequate contact between sod and the soil, irregularities in the soil should be removed prior to application by smoothing and firming the soil with lightweight equipment.

Installation

Sod should not be applied on compacted soils, frozen soils, or on areas that have been treated with pesticides. Sod should be installed from March 15th to October 20th. However, installation may take place outside of these dates as long as temperatures remain above freezing and at least 30 days are available for establishment.

Sod should be applied in a brick-like pattern perpendicular to the direction of flow. Care should be taken to avoid stretching and overlapping the sod. Joints in the sod should be tightly butted together, with angled ends overlapping each other. The sod should be moist and, on hot days, stored in the shade prior to application. The soil should also be watered lightly before installation to cool the soil and ensure the health of the roots.

On slopes, installation should begin on the downslope edge and proceed upslope. On slopes that are steeper than 3:1 or in areas of concentrated flow, sod should be anchored with pegs or netting.

After application, the sod should be rolled and irrigated until the soil is damp 4 inches below the surface. Irrigation should continue until the sod has become firmly rooted. Rolling, performed with a lightweight implement, encourages contact between the roots and the soil surface, while irrigation provides a favorable medium for growth. Together, these practices should ensure the successful growth of the sod and the erosion control capabilities of the vegetation.

Construction

  • All tracking and grading should be completed before sod is installed
  • Sod should be installed no more than seven days after final grading of the site
  • All management practices should be installed and online before sod is applied
  • Surface should be adequately prepared and cleared of all trash and debris before sod is installed
  • To promote growth, sod should not be installed during excessively wet or dry conditions

Maintenance

  • Inspect sodded areas after all storm events for damage and repair or replace as necessary
  • Sod requires at least 1 inch of water per week to become properly established
  • Add fertilizer as necessary at proper rates
  • Mowing should not be attempted for at least 3 weeks after application and should not at any time remove more than 1/3 of the shoot (grass should be maintained with a height of 2-3 inches)

Method to Determine Practice Efficiency

The efficiency of this practice is derived from reducing the amount of time that the site is left bare and exposed. Soil loss effectively ends with sod installation, which shortens the exposure time by 60 days when compared to seed and mulch.

To determine the efficiency for this practice, use the new, shortened exposure time and replace the pre-existing one in the USLE and recalculate. The difference between the two equations is the efficiency for the practice.