What Do I Need To Know About Hydromulching?

Spray Grass Australia (SGA) have been experts in their field for over 25 years; they offer a range of hydroseeding and hydromulching solutions for the most confronting environmental issues across Australia. Over this time, the team have developed innovative solutions to maximise on client objectives and meet varying environmental conditions. To assist you with your next revegetation project, discover everything you need to know about hydromulching with our most frequently asked questions.

What is hydromulching?

Hydromulching is a technique involving the hydraulic application of seed, water, wood fibre mulch, and often tackifiers, fertiliser and tracking dye onto often depleted soils. Clients choose this solution over traditional methods based on the added much, which offers erosion control, soil stabilisation and seed protection from wind and rain. The mulch consists of long length mulch with interlocking organic fibres designed to permeate into the soil surface, ensuring consistent infiltration of water and airflow.

Two types of hydromulching solutions are offered depending on the substrate variables – these include:

• EnviroLoc – Hydromulching BFM (Bonded Fibre Matrix)
• Enviro Pro – Hydromulching GHM (Hydraulic Growth Mediums)

What is the difference between hydromulching and hydroseeding?

These terms are used interchangeably and are effective alternatives to traditional planting processes, such as sod applications, drill seeding or hand seeding. There is however, a core difference between a hydroseeding and hydromulching solution.

Hydromulching solutions consist of hygroscopic fibre-mulch with the seed, fertiliser and water mix, where hydroseeding does not. Hydroseeding is suited to large areas where the physical characteristics of the soil profile are balanced, quality irrigation is present, and mulch is not required.

What is the purpose of hydromulching?

Hydromulching is the supporting process for revegetation, used to help establish seed germination by providing environmental protection and erosion control. We recommend hydromulching to sites with uneven or steep and highly erosive slopes that have experienced soil disruption due to mining, construction or infrastructure works.

If bare and disrupted soil is left unattended environmental damage such wind and rain erosion may cause sediment and debris movement into streams, creeks, lakes and oceans. Hydromulching is the initial stage to prevent such issues from occurring by protecting the soil until vegetation is strong enough to stabilise the mechanical structure of the substrate.

This solution also helps in the civil industry to absorb moisture from rain, snow and frost, which could weaken and damage the road foundation.

What benefits does hydromulching offer?

Hydromulching is a suitable revegetation approach which offers several benefits, including:

• Erosion and seed protection
• Dust suppression
• Hygroscopic properties – providing up to 50 % more water retention than traditional mulches, allowing for faster germination and growth
• Maintains moisture temperature for optimal vegetation growth and environmental support
• Eliminates pathogens and weed growth
• The organic mulch fibres are non-toxic and will degrade over several months, making way for vegetation growth

What preparation is required?

Planning:
Early rehabilitation plans will provide sustainable management for native vegetation and environmentally sensitive areas. This preparation will ensure that an environmental specialist can promptly remediate and prepare solutions for disrupted soils caused by land clearing and other significant site modifications.

Soil testing:
Soil testing is an essential process in all revegetation and hydromulching programs. This procedure looks closely at the soil characteristics and determines any imbalances that may affect vegetation growth – these variables may include potential hydrogen (pH), fertility, microbial activity and differing soil nutrients. Once a scientific analysis has determined the soil profile, a soil amendment strategy is prepared and implemented to support the hydromulching efforts.

Note: if the soil is beyond repair a topsoil alternative, may be required to enable vegetation growth. SGA offers EnviroSoil®, an engineered biotic topsoil with customised amendments designed to improve weak soils that lack nutrients and bioactivity.

What is the process of application?

Project applications can be conducted over one application pass depending on the client’s site requirements; however, generally, a two-part process chosen for sites located within harsher environments. All hydromulching solutions are implemented with SGA’s purpose-built HydroRigs™, designed to hydraulically apply the product evenly onto the substrate area.

Part 1: Seed, Amelioration and Fertiliser Program
The first application process consists of a custom seed mixture to ensure an optimal seed to soil contact ratio. Depending on the condition of the natural soil profile, a tailored amelioration and fertiliser solution may be added to the seed mixture if the soil is lacking in vital active botanicals. These adjustments could include trace elements, soil conditioners, and probiotics for critical nutrients, growth, and seed strike rates.

Part 2: Hydromulching
The second stage involves the application of the hydromulching solution. The mulch will provide broad coverage, acting as a safeguard for the seed by helping it to retain moisture for faster growth while shielding the soil and seed placement from wind and rain erosion.

The solution will mould to the contours of the surface substrate, including high gradient batters and uneven topography. This two-part process takes into consideration the erosion control effectiveness, ability to facilitate growth and the functional longevity for successful rehabilitation of the area.

Equipment:
This application process will use SGA’s entirely mine compliant HydroRigs™ known for their sleek design, power, and speed. This equipment will eliminate the need to work on steep slopes and can provide fast and adequate coverage. The purpose-built trucks have built-in agitators within the holding tanks intended to mix the product for an even hydraulic application. The vehicles can apply product via cannon at a distance of 100 meters and up to 400 meters with the hose attachment. These distances allow for up to 50,000+ square meters of coverage per day.

What is the best season to apply a hydromulching solution?

Choosing an appropriate time to hydromulch is crucial to the growth and long-term results of all rehabilitation projects. Australian conditions do vary from state to state, therefore recommended seasonal periods will differ depending on your site location; however, you should consider the following weather advice before committing to a hydromulching project.

Rainfall is a significant factor in developing vegetation growth; therefore, we would recommend avoiding application during the dryer seasons where irrigation is required, as this will add to water consumption and labour costs. On the other hand, wet seasons with too much rain has the potential to wash mulch, seed and topsoil nutrients away. If the application must occur around anticipated heavy rain events, we will recommend a higher application rate accompanied with additional mulch and binders to withstand the disruption of rain impact.

The hydromulch will act as insulation to the seed, however, if the average temperature is too low, this will alter the seed strike rate, and if the temperature is too high moisture will evaporate, resulting in limited to no growth.

Project locations within the mid to northern parts of Australia should time hydroseeding between winter through to late spring before heavy summer rains reach your project site. Around this time, the temperature is low enough to enable vegetation before warm summer weather arrives.

Depending on your site location, all these variables are taken into consideration and discussed carefully with the client. Our team have a range of suitable solutions depending on what season you are planning to commence work. You will find that various seasons offer different advantages for each solution.

What type of aftercare is required?

If hydromulching is taken place in the appropriate season to accommodate environmental conditions, minimal site maintenance will be required. In most cases, natural rainfall will provide adequate water filtration; however, if your site location lacks in regular rain and is accompanied with severe heat, the mulch is likely to dry out and affect seed germination.

If this is a concern for the client, the team at SGA will work with them to develop a comprehensive irrigation plan to help achieve site objectives.

What type of seed is required?

Native seed species are often the primary choice; however, if onsite soil testing indicates extreme imbalances such as increased salinity, waterlogging or lack of nutrients, the seed variety may be altered to align with the quality of the soil.

The decision-making process also considers several factors, including project location, site conditions, environmental circumstances, the intended use of site and maintenance requirements, all of which will be looked at in-depth to safeguard success. Any site alteration will affect what vegetation will be able to germinate on site.

How long will It take to produce vegetation?

The growth rate of seed post-application is dependent upon, weather conditions such as rainfall, sun exposure and temperature. Providing that the product solution is applied within an optimal seasonal period, signs of vegetation growth will be evident in most locations within 1-2 week, with optimal coverage present between 4-6 weeks.

Why is the hydromulching mixture green?

Most hydromulching solutions include a non-toxic green dye; this is added to the mixture to ensure that technicians can see where the product has reached, preventing overspray and confirming that areas haven’t been missed.

If you require further information on our hydromulching solutions, please contact the team today.