Wet Mulch (Hydromulch)
What – Combinations of organic fibers (e.g., wood shreds, paper, cotton, flax, etc.), tackifiers (i.e., glue), suspension agents, and seeds are mixed together with water and applied to the soil surface via ground or aerial applications.
Purpose – The matrix formed by hydromulch creates an immediate cover and holds moisture and seeds on steep slopes, which fosters seed germination while holding soil in place.
Effectiveness – Hydromulch may reduce sediment yields during the first few rainfall events (long-term effectiveness is unknown). Treatments are more effective on short slope lengths vs. longer slopes due to susceptibility to concentrated flows. This method is wind resistant. Multiple factors impact effectiveness (e.g., application rates, slope length and steepness, make/brand of tackifier).
Where
- Aerial application on inaccessible, highly erodible soils following moderate or high fire severity.
- Ground application on highly erodible soils near roads.
- Due to cost, there usually needs to be prioritization for mulch application, focusing on where there is a threat to life and property. This may include steep slopes adjacent to communities, roads, and infrastructure; also critical headwaters that feed municipal water supplies, and waste sites that pose serious environmental threats.
Cost – $2000–3000 per acre for aerial application; $1675–3000 per acre ground application. Additional factors include:
- Location and access
- Helicopter/fixed-wing aircraft turnaround time
- Helicopter/fixed-wing aircraft production rate
How to Links – See USDA BAER Catalog pages 15 and 22 (PDF pages 23 and 30); and NRCS Hydromulching Fact Sheet.