What Are The Most Common Mulches Used For Hydromulching?

Mulch has provided a means of mitigating the effects of erosion for decades, based on the benefits associated with hydromulching for revegetation. It is commonly applied using purpose-built HydroTrucks to hydraulically disperse mulch with water, seed and fertilisers, onto disturbed soil or steep slopes, to avoid excess loss of sediment. Depending on the site characteristics, additives and binders can be included to underpin vegetation growth.

With such a leading methodology in place nationally, it is essential to understand what type of mulches are available on the market and which one will provide optimum results. With dryer weather conditions combined with low annual rainfall, Australian companies are looking for innovative methods such as hygroscopic mulch, with the ability to retain moisture for seed germination, provide nutritional value, suppress weeds, deliver optimum erosion control, while underpinning environmentally sustainable properties.
Each distinctive mulch offers a combination of variables, benefits and uses; however, finding the right one can be challenging to identify. The following options will provide greater insight into which solutions may be best for your environmental conditions.

Common Mulches Used For Hydromulching

Sugarcane is a popular choice of mulch, prominently found within regions of Queensland, Australia, where it is primarily grown as a native resource. The mulch is a by-product produced after the sugar is extracted from the stalk – this is referred to as bagasse, which is the dry fibrous pulp remaining at the end of the process.
Similarly, to wood, steam or heat-treated bagasse is generally superior to non-treated alternatives, having elevated water retention and fibre properties. The sugarcane mulch can retain up to around seven times its weight in water and has a generous fibre length, making it suitable for use during the application of hydromulching. The sugarcane is harvested extensively higher than general weed growth; therefore, there is no transferal of seed within the mulch.

Straw Fibre
Heat-treated straw mulch is a contemporary implementation into mulch alternatives, with a notable increase in use over the last ten years. The interlocking fibres produce essential coverage for weed control and provide insulation during unpredictable weather conditions. With the ability to hold around five times its weight in water; it can release this moisture somewhat more progressively than other mulches, which allow the water to be better utilised. The straw fibre is primarily a considered mulch option based on the low carbon footprint produced during development.
Unfortunately, as the straw naturally breaks down and decomposes, it provides little to no added minerals or direct nutrients value into the substrate below, which can affect the soil profile. Due to the larger volume of the natural straw fibres, they are unable to provide ample coverage and therefore require significant amounts of the product to achieve optimal growing conditions.

Traditionally cotton hydromulch is derived from the husks and hulls of cotton plants. Due to its distinctive positive characteristics such as superior water retention and erosion control, this much has gained significant support from the environmental sector. However, due to the costly nature of the mulch, it has been disregarded as a primary hydromulching solution for many potential buyers.
Recyclable cotton waste is a recently considered hydromulching approach due to its ability to cover a vast scope of substrate for a portion of the cost compared to traditional mulches. This innovative solution is ideal for steep inclines and flat to mid-slope terrain. Although cotton waste has vital sustainability benefits, it does not provide additional nutrient value to the soil as it decomposes.

Paper Pulp
Paper pulp mulch is the most economical and environmentally-friendly form of mulch; however, arriving in a two-dimensional matrix, it lies flat on the ground removing its ability to provide effective erosion control. The paper pulp is also unable to maintain acceptable water retention; therefore, when it dries, it forms a ‘paper mâché’ like appearance, rendering it difficult for new growth to penetrate the surface crust.
If the paper pulp is considered for hydromulching purposes, we recommended only to apply it on a flat or gently sloped area (less than 4H:1V), where an irrigation system is in place to guarantee that the paper remains consistently damp.

Wood Fibre
Wood fibre mulch is derived from hard and softwood timber and occasionally obtained from post-consumer wood waste. The most viable option is heat-treated wood placed under pressure, which enables the production of long wood fibres with a higher water-holding capacity, capable of retaining up to 10 times its weight. This type of mulch has the ability to maximise on contact with the substrate, particularly on vertical slopes, for superior protection and durability. Organic wood fibre mulches are the most common form used for hydroseeding; however, it is vital that you can source the most effective product material.

Option 1 - Atmospherically Refined Wood Fibers

Option 1: Atmospherically Refined Wood Fibers
As depicted on the left, atmospherically refined mulches are derived from compressed hardwood, generally, approximately 1mm long, therefore providing minimal coverage, suggesting that more product is required to achieve successful results. When much is in this form, it results in 50% lower water holding capacity than refined mulches; therefore, effecting vegetation growth practically in harsher Australian landscapes.

Option 2 - Thermally Refined Wood Fibers

Option 2: Thermally Refined Wood Fibers
Demonstrated on the right are thermally refined wood fibres, primarily derived from soft compression wood. These fibres can swell and due to their helical structure are capable of twisting and push the adjacent threads in the opposing direction. These three-dimensional refined wood cells constitute the primary building blocks in successfully engineered wood-based mulches, with variables such as renewability, stiffness, strength and insulation. Softwood fibres generally consist of finer intertwining properties between 2-3 mm in length – this enables them to cover a greater surface area which underpins seed germination by providing an essential barrier from varying weather conditions.

• Consistent soil contact
• Durable erosion control
• Maximum matting ability, providing effective soil insulation for seed germination
• More coverage with less product
• 50% more water retention than traditional wood fibre mulches
• Suppresses weed seed growth
• Allows for uniform product distribution, helping to cover increased ground rapidly
• Lower total project cost

Based on the above analysis, several mulch options may be viable for your site requirements; it does, however, depend on what you are looking for when it comes maximising on your results. Erizon has a dedicated team of environmental consultants that will be able to help you make the right decision. The team have the following two Hydromulching options available, which can be tailored to meet your goals and objectives.

Enviro Loc – Hydromulching Bonded Fibre Matrix BFM
EnviroLoc is a heavy-duty growth medium, designed to complete a combination of two passes over the substrate area. The first step involves a mixture of water, seed, and ameliorates being hydraulically applied onto the surface to ensure sufficient seed-to-soil contact. The second step consists of using cellulosic mulch and proprietary binder and tackifier at a high application rate to ensure optimum erosion control. The BFM’s viscous bonding agent dries to form a protective skin over the treated surface area, while interlocking fibres work to maintain a high level of moisture which fosters an ideal growing environment.

Enviro Pro – Hydromulching Hydraulic Growth Medium (HGM)
Enviro Pro is hydromulching in a one-step process, designed to be hydraulically applied with water as a carrier, seed, fertiliser, binder, cellulosic mulch, tracking dye and a distinctive mix of fibres to develop HGM on areas with slopes of up to 3h:1v. The blend of both chemical and mechanical bonding methods is what locks the engineered growth medium in place to stimulate germination with reduced soil loss levels. HGM is capable of not only improving the soil structure more quickly but also uncovering nutrients and creating a mutually beneficial relationship with the target crop, for better resilience to stressful conditions – this is a viable option for revegetating vast expanses of land quickly and efficiently, despite whether your site requires flat or vertical coverage.

Please note it is always essential to gain a second opinion from an environmental consultant before going ahead with your purchase; this process will save you time and money in the long run. If you need assistance, finding an environmental solution that is suited to your environmental conditions, contact our dedicated team today.

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