- Barrier Aesthetics
- Blue Star Memorial Highways
- Classified Landscaped Freeways
- Community ID
- Context Sensitive Solutions
- Erosion Control Toolbox
- Gateway Monuments
- Main Streets
- Mission Bells
- New Product Review
- Policy and Procedures
- Roadside Toolbox
- Safety Roadside Rest Area System
- Scenic Highways
- Transportation Art
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- VIA Training
- Water Conservation
Erosion Control Toolbox
To Combine Specifications
Planning & Design
Improve Soil Health
- Soil Rehabilitation
- Local Topsoil
- Imported Topsoil
- Roughen Soil Surface
- Stepped Slopes
- Contour Grading and Slope Rounding
- Decompact Soil
- Incorporate Materials
Improve Soil Health & Provide Cover
Short Term Cover
Long Term Cover
Steep Slope Techniques
- Stepped Slope
- Cellular Confinement
- RECP Flap
- RECP Flap with Brush Layering
- RECP Wrap
- Soil Filled RSP
- Wire Blanket
- Wire Mesh Confinement
- Plant Selection
- TransPlant Application
- Noxious and Invasive Species
- Drill Seed
- Dry Seed
- Native Grass Sod
- Brush Layering
Low Impact Development
- Sidewalk Stormwater Planter
- Sidewalk Stormwater Tree Trench
- Parking Stormwater Planters
- Permeable Paving
- Additional Resources
What is This Treatment?
This work typically involves mixing compost, mulch, and/or straw into the soil surface. Depth of incorporation varies by slope gradient - steeper slopes involve lesser incorporation depths. Compost is typically mixed at a ratio of 30% compost to 70% soil, the rate of other materials varies. See the Application Rate Guidelines below for detailed
When to Use This Treatment:
- Typically used for slopes 2:1 (H:V) and flatter. Guidance on rates and depths is provided in the table at teh bottom of this page. For specific maximum rates and slope gradients, consult your geotechnical engineer.
Reduced stormwater runoff volume and velocity.
Improved infiltration rate.
Improved soil water holding capacity.
Improved soil structural properties - soil structure, porosity, and texture.
Improved plant rooting depth.
Improved soil chemical properties - providing proper pH, carbon, nitrogen, potassium and phosphorus levels.
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.
May require temporary storage space within the project limits to stockpile materials.
Requires site accessibility by earthwork equipment.
Applying high levels of organic materials may not be appropriate in arid regions of the state.
- When incorporating compost, suppliers must be participants in the United States Composting Council's (USCC) Seal of Testing Assurance (STA) program. A list of current STA program participants is available at: US Composting Council (USCC) Seal of Testing Assurance (STA) Program Participants
Select the equipment to incorporate compost and other materials based upon the steepness of slope, depth of incorporation, site accessibility, and equipment availability. The photos below highlight these factors with regard to typical equipment type.
Rototilling (shown above) can be used to incorporate materials to shallow depths (less than 8 inches) in flat project areas. Rototilling is very effective at mixing materials with topsoil, but is ineffective at greater depths.
Construction equipment (such as the bulldozer-attached chisel plow shown above) is good at ripping, loosening or decompacting the soil surface, but is not effective at "incorporating" or "mixing" materials with topsoil. In short, ripping tines do not mix soil amendments.
A tractor drawn disk set (shown above) is a cost-effective method to incorporate materials for large flat areas, but is limited to a depth of 6" to 12" and does not mix materials as well as the tracked excavator shown below.
A tracked excavator with bucket attachment (as shown above) can be used to incorporate materials on steeper slopes to depths of up to 3 feet. This approach is much more effective at mixing materials than rototilling or ripping, however the equipment is more costly. An additional benefit is that the irregular nature of this technique reduces the likelihood of creating a slip plane between the amended and non-amended soil layers.
Video - Incorporating Materials With an Excavator
Compost Application Rate Guidelines
A number of methods can be used to determine the compost application rate that will provide the total Nitrogen/acre necessary for the sustainable establishment of vegetation.
1. Soils Test
The best way to determine the appropriate application rate for compost is to perform a soils test. If a soils test is not feasible, the following alternate methods may be used to quickly estimate the ideal compost application rate.
2. Ecosystem Based Soil Nitrogen/Acre Requirement
The compost application rate may also be quickly estimated based upon the typical total soil nitrogen requirement for vegetation in an ecoregion. See the table under #3 below to determine the compost application rate that correlates with the desired Average Total Nitrogen LBS/Acre.
|Ecoregion||Average Total Nitrogen
|Minimum Total N required to support vegetation as identified by Bradshaw and others (1982)||625|
|Drastically Disturbed Sites||700|
|Minimum Total N required to support vegetation in decomposed granite soils as identified by Claassen||1,100|
|Shrub -Steppe Prairies||4,500|
|Deep Forest Soils||20,000|
3. Minimum Soil Organic Material (SOM) Requirement
The ideal compost application rate may also be quickly determined by correlating it with the typical minimum soil organic material (SOM) required to sustain healthy vegetation. While the ideal organic material (SOM) content varies based upon the specific ecoregion vegetation and soil type, research indicates that a typically sound SOM range is between 8-13%, which typically equates to 30% compost by volume in the soil.
Keep in mind that during the first growing season, seeded disturbed soil areas typically exhibit sparse vegetative cover, thus requiring very low available nitrogen levels - often just 50 pounds/acre. Nitrogen applied that exceeds plant requirements will not be utilized for plant growth and may leach to lower soil horizons thus becoming unavailable for future plant growth.
Application rates below are based upon a target Soil Organic Material (SOM) rate of 8-13%, a Total Nitrogen/Acre range of 1,000 - 3,000 lbs/acre, and an available Nitrogen amount of 100-300 lbs/acre. Lower application rates are recommended in arid regions, or areas that typically receive less than 10 inches of precipitation per year. Higher application rates are recommended in decomposed granite soils, or in ecoregions that must support dense vegetation such as coastal forests. Specific site conditions as well will modify these general recommendations. Stability requirements for slopes 2:1 (H:V) and steeper, for example, will constrain incorporation depths. Coordinate the use of Incorporate Materials with Caltrans Division of Engineering Services (DES) Office of Geotechnical Design.
N / AC
N / AC
|1" Compost incorporated
in top 3" of soil
|135||52||1,080 Lbs||108 Lbs||8-13%||2:1|
|2" Compost incorporated
in top 6" of soil
|270||96||2,160 Lbs||216 Lbs||8-13%||3:1|
|3" Compost incorporated
in top 9" of soil
|405||162||3,240 Lbs||324 Lbs||8-13%||4:1|
|4" Compost incorporated
in top 12" of soil
|540||216||4,320 Lbs||432 Lbs||8-13%||4:1|
Consider Using With:
To provide protection for the soil surface, consider combining this treatment with:
Plans and Details:
The image below is an example of how to specify the incorporation of various materials on project plans:
- Typically $0.35/SF (2013).
- Use BEES code 210630, Incorporate Materials
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 how compost improves the establishment of permanent vegetation cover.
Regeneration of Nitrogen Fertility in Disturbed Soils Using Compost
Graphs nitrogen release from various composts and compares compost release rates with two native topsoils.
- David Steinfield, Scott Riley, Kim Wilkinson, Thomas D. Landis, Lee Riley, et al. 2007. "Roadside Revegetation, An Integrated Approach to Establishing Native Plants" Accessed 2009-07-16
- Michael Hogan, 2009. "Sediment Source Control Handbook, An Adaptive Approach to Restoration of Disturbed Areas" Accessed 2009-07-16.
- US Composting Council Seal of Testing Assurance, Compost Producer Participants Accessed 07-16-2009.
- Compost Use for Landscape and Environmental Enhancement Manual
The California Integrated Waste Management Board's Compost Use for Landscape and Environmental Enhancement publication provides objective information regarding compost use in landscape planting and environmental applications.
- Multipurpose Subsoiling Attachments
New methods of soil decompaction developed by the Forest Service to cut costs and to ensure satisfactory results. These operations return of soil tilth (the physical condition of soil as related to its ease of tillage, fitness as a seedbed, and its impedance to seedling emergence and root penetration) to compacted soil.