Typical 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.

Common Mulches Used For Hydromulching

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 drier 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.

Sugarcane

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.

Similar 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 10 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 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.

Cotton

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 recommend 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 Fibres

As depicted at the top, 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, affecting vegetation growth practically in harsher Australian landscapes.

Option 2: Thermally Refined Wood Fibres

Demonstrated at the top 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 pushing 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.

Benefits

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 to maximising on your results. Erizon has a dedicated team of environmental consultants who will be able to help you make the right decision. The team has the following two Hydromulching options available, which can be tailored to meet your goals and objectives.

Hydromulching Options

Below is a brief description of the hydromulching products that we use in our hydroseed slurry. Our team of experts can help you choose the right hydromulch to ensure the success of your project.

  • EnviroLoc – 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.

  • EnviroPro – Hydromulching Hydraulic Growth Medium (HGM)

    EnviroPro 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.

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