A straw blanket, also known as an erosion control blanket, is a temporary rolled matting designed to stabilize disturbed soil and protect it from the erosive forces of wind and water. This product is composed of agricultural straw fibers mechanically stitched between layers of netting, creating a cohesive structure. Its purpose is to slow down water runoff, shield the soil surface, and prevent the displacement of fine particles and seeds. By holding the soil in place, the blanket fosters a microclimate that enhances seed germination by retaining moisture and moderating soil temperature.
Preparing the Site and Selecting the Right Blanket
The site must be cleared of all debris, including large rocks, tree roots, and any existing vegetation that could prevent the blanket from making full contact with the soil surface. Proper soil contact prevents water from channeling underneath the matting, which would undermine erosion control. The prepared area should be lightly graded and raked to create a smooth, firm seedbed, which is often done after seeding and fertilizing the soil.
The appropriate blanket must be selected based on the steepness of the slope and the anticipated water flow. For flatter areas or gentle slopes up to a 3:1 ratio (three feet horizontal run for every one foot vertical drop), a single-net straw blanket is generally sufficient. For steeper slopes, high-flow channels, or areas with more intense water velocity, a double-net blanket, which sandwiches the straw between two layers of netting, offers greater tensile strength and stability.
Consideration should also be given to the netting material, especially in environmentally sensitive areas. While some netting is photodegradable plastic, which breaks down over time with exposure to ultraviolet light, biodegradable options made from organic fibers like jute or coir will fully decompose. Choosing a fully biodegradable blanket eliminates the need for removal and prevents the possibility of wildlife entanglement that can occur with persistent plastic netting. The choice of netting directly influences the blanket’s lifespan, which can range from 45 days for rapid-degrade options to over a year for standard biodegradable versions.
Step-by-Step Installation and Securing Techniques
Installation must always begin at the top of the slope or the highest point of the area to be treated, ensuring a correct shingling effect. The method for securing the uphill edge involves trenching, where a slot approximately six inches deep and six inches wide is dug across the top of the slope. The blanket’s end is placed into this trench, secured with staples, and then the trench is backfilled and compacted to create a secure anchor that prevents water from flowing beneath the blanket’s upper edge.
The blanket should be unrolled straight down the slope or parallel to the direction of water flow, taking care not to stretch the material during placement. Maintaining a relaxed lay ensures the blanket molds to the soil contours, which maximizes surface contact and effectiveness. If multiple blankets are needed to cover the width of an area, subsequent rolls must overlap the first, following the shingling principle.
Side-by-side seams should overlap by a minimum of four to six inches, while end-to-end overlaps typically require a more substantial overlap of 12 inches. Securing the blanket to the soil is accomplished using U-shaped or V-shaped metal staples, which should be driven until they are flush with the ground surface. The density of staples is determined by the slope and potential for water movement, with flatter areas requiring fewer staples than steep slopes or channels.
A general guideline is to secure the body of the blanket with staples placed every two to three feet, using a staggered pattern to enhance stability. However, the overlaps and all edges, including the sides and the trenched ends, require much tighter spacing, typically with staples placed every 12 inches to prevent lifting.
Post-Installation Care and Natural Degradation
Immediately following the installation of the straw blanket, the area should be thoroughly watered to settle the soil and the matting. Consistent moisture is a determining factor for successful seed germination, which is the long-term solution for erosion control. The blanket acts to slow the rate of evaporation, but the soil beneath must be kept moist, not saturated, to encourage the seedlings to establish strong root systems.
Regular monitoring of the installed area is necessary, particularly after heavy rainfall events. Inspection should focus on the seams and edges, checking for any signs of uplift, displacement, or water channeling underneath the material. Any areas where the blanket has lifted should be immediately restaked to restore full contact and prevent the formation of rills or gullies.
The straw fibers within the blanket are designed to naturally break down over time, returning organic matter to the soil as they decompose. The lifespan of a straw blanket is temporary, generally lasting between three and twelve months, depending on the material of the netting and local environmental conditions like climate and UV exposure. Once the underlying vegetation has grown sufficiently to stabilize the soil, the blanket’s purpose is fulfilled, and the remaining netting will continue its natural degradation process, leaving behind a fully vegetated, stable surface.