Compost

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The compost bid item refers to two distinctly different types of work. Compost may either be applied as a mulch-like blanket, typically 2" thick, onto disturbed soil areas, or it may be applied to a slope and then mixed together with other materials (such as bark, straw or topsoil) when used with Incorporate Materials. Payment for compost material is made via the compost bid item described here. A compost blanket provides several benefits, including protecting bare soil surfaces from wind and water erosion, water conservation, weed control, and providing nutrients required for long term, sustainable vegetation. By being closer to the plant root systems, compost used with Incorporate Materials provides a source of nutrients required for establishment of vegetation.

When to Use These Treatments

  • Use compost where disturbed site soils are sterile, compacted, and/or low in nutrients
  • Compost blankets are typically applied to slopes 1.5:1 (H:V) and flatter. The following application rates are suggested:
    • Slopes 1.5:1 (H:V) - 1" maximum thickness
    • Slopes 2:1 (H:V) - 2" maximum thickness
    • Slopes 3:1 (H:V) - 3" maximum thickness
    • Slopes 4:1 (H:V) - 4" maximum thickness
  • For guidance on determining the compost application rate for optimal plant growth, see the Application Rate Guidance section of the Incorporate Materials web page

Benefits of Compost Blankets

  • Improved protection from raindrop splash erosion
  • Reduced competition from weed species
  • Reduced stormwater runoff volume and velocity
  • Improved infiltration rate
  • Conserves soil moisture
  • Improved soil biology - activity by bacteria, mycorrhizal fungi, nematodes, protozoa, microarthropod and earthworms
  • Improved soil nutrient levels and nutrient cycling
  • Improved potential for vigorous long term vegetation coverage

Compost Blanket Limitations

  • Compost may blow away in high wind areas - consider tacking in place with Hydromulch, or covering with RECP Netting (Type A)
  • Temporary storage within the project limits may be required to stockpile the compost
  • Compost may require additional erosion control treatment in areas with significant rain events

Design Considerations for Compost Blankets

  • Verify compost availability - check producers list at: US Composting Council (USCC) Seal of Testing Assurance (STA) Program Participants
  • Determine if new slopes will require incorporation of organics to support sustainable vegetation
  • Specify "Medium" or "Coarse" compost materials for compost blanket work to minimize the loss of compost due to wind

 

The photos below highlight common erosion control combinations, together with their strengths and weaknesses.

Compost Blanket

This photo shows compost applied to a slope as a blanket, with no additional treatments layered on top. If compost is being applied with a pneumatic blower truck, the seed can be placed in a side bin in the blower truck and applied together with the compost in a single step. For this method, all slope areas must be within 300 feet from the blower truck as the blower truck hose is just 300 feet long. If the slope to be treated is located below a roadway, compost can be dumped from the roadway onto the top of the slope and drawn down the slope with rakes.

Compost Blanket, Straw, Incorporated (Or Crimped)

This photo shows a 2” Compost Blanket, topped with blown Straw, then Incorporated in place with a crimper. The crimp adds an additional step for the Contractor with an additional piece of equipment and can be costly. For most sites, a more cost effective approach to hold the compost in place is shown directly below.

Compost Blanket, Straw, Tacked With Hydromulch)

This photo shows a 2” Compost Blanket, topped with blown Straw, and held in place by applying a layer of Hydromulch (a combination of tackifier and fiber). This combination of "S" treatments is very cost effective and reliable for 2:1 (H:V) slopes up to 30 ft in length. Straw is excellent at protecting the soil and compost from raindrop erosion while providing a mulch for effective seed germination. For very windy sites, consider the approach below.

Compost Blanket, Rolled Erosion Control Product (RECP)(Netting)(Type A)

This photo shows a 2” compost blanket covered by RECP(Netting)(Type A), a costly but effective method of preventing erosion and keeping compost and seed in place in areas subject to high winds and/or highly erosive rain events. In the photo above, compost berms are used instead of fiber rolls. It is recommended to apply the RECP(Netting)(Type A) on top of both the compost blanket and berms. This method is more cost effective than placing the compost berms on top of netting and reduces the likelihood that the compost berm will biodegrade the netting.

Coarse Compost And Trash Content

It is possible to purchase medium or coarse compost with low trash content, but coarser compost materials often have a higher level of trash (plastic) than fine compost products. Compost producers can remove trash (plastic) during the production process, but this increases cost. If you cannot obtain medium or coarse compost free of plastic, another approach is to specify fine (3/8" minus) compost materials covered with bark mulch, and then use Incorporate Materials to combine the materials in place. This way you get the benefits of a coarser compost product with less trash.

Compost Calculator

Depth Enter design depth.
Area (SF) Enter area in square feet. For example 1 acre = 43560 square feet.
   
Cubic Yards  
Cubic Feet  

Common Compost Application Rates

Compost Depth Cubic Yards/Acre Pounds/Acre Tons/Acre
1/2" 68.5 54,800 27
1" 135 108,000 54
2" 270 216,000 108
3" 405 324,000 162

Average Compost Weight = 800 lbs/cubic yard (1050 lbs/cubic meter)

Compost Application Methods

 

Large quantities of compost required for compost blanket can be applied to a flat project site using a dump truck and a bulldozer. Sites with steep slopes or areas inaccessible by vehicles require alternate methods such as a pneumatic blower truck.

A pneumatic blower truck rapidly applies compost to steep slopes or areas that are inaccessible by equipment. A 40 cubic yard blower truck holds roughly 35 cubic yards of compost, and applies material at a rate of about 35 cubic yards/hour. A single truck should be able to apply a 1" thick compost blanket over a 2-acre site (280 CY total) in a single working day. The truck hose can reach 300 feet, which is the maximum distance that can be reached from the roadway. A rough estimate of cost for labor and materials for this work would run from $5,000 - $8,000 per acre.

Consider Using With

To hold compost in place on steep slopes or to protect from wind erosion, consider combining compost with:

To effectively treat sites with compacted, sterile or poorly draining soils, consider combining this treatment with:

Plans and Details

Estimate Information

  • Use BEES code 210610 Compost

Research

Model Guided Specification for Using Compost to Promote Establishment of Vegetation and Stormwater Quality Improvements, 2010

This study establishes parameters for compost use based on performance criteria including soil type, climate, slope length and steepness, aspect, and location. The research addresses how compost affects water quality and erosion, and if it improves the establishment of permanent vegetation.

Regeneration of Nitrogen Fertility in Disturbed Soils Using Compost
Graphs nitrogen release from various composts and compares compost release rates with two native topsoils.

References

 

Updated: December 6, 2018

 

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