Hydromulching
Introduction
A special blend of mulches, water, seed, fertiliser and binders (Tackifiers) are mixed into a slurry and then sprayed onto a seed bed. Properly specified and applied the mulch protects the soil from erosion and aids in moisture retention assisting seed germination.
Site Preparation
Where possible, topsoil should be spread prior to hydromulching. It should be noted that hydromulching is not a 'magic' solution. Site soil must be capable of supporting vegetation growth for hydromulching to be successful. If there is no quality site-soil available, a layer of topsoil will need to be applied prior to hydromulching. Should the subgrade be compacted, then the area will require scarifying prior to spreading of the topsoil. Where topsoiling and scarification are impractical, hydromulching can still be used with higher seed rates and additional ingredients to assist in plant establishment.
Hydromulching Ingredients
i. General
Mulch mixtures vary from recycled paper (cellulose) to wood and other organic fibres such as sugar cane mulch. Synthetic fibres can also be added to increase the strength of the mulch. Prior to recent developments paper mulch was primarily used with Bitumen Emulsion as the binder. Better results have recently been achieved using other organic mulches which have longer fibres.
ii. Paper Mulch
This type of mulch was previously the most popular product used in Hydromulching due to its availability and low cost. In warmer climates, it was found to be less effective as it drew moisture from the soil as it dried. Consequently, extra post installation watering is required to ensure high seed germination rates. Paper mulch also has a much shorter fibre than some other organic mulches and therefore we do not recommend it to be used on batters.
iii. Woodfibre Mulch
Recent developments have seen an increased use of these products in hydromulch. Woodfibre has much longer and stronger fibres than paper mulch and has better moisture retention. Much of the woodfibre used is imported and can be quite expensive. We therefore recommend that it is blended with other locally produced organic mulches.
iv. Sugarcane Mulch
Fine chopped sugarcane mulch is an excellent product when used in combination with other products. Being readily available and inexpensive, sugarcane mulch has long durable fibres which when combined with other fibres make a strong matrix to protect both the soil and the new seed.
v. Seed Mix
Most seed types can be applied through hydromulch with seed selection being varied to suit local soil and climatic conditions. It is advisable to use some form of fast germinating cover crop to give protection to the soil and the permanent species as they establish. This cover species should not overly compete with the other plants and therefore application rates should be carefully monitored. Cover species will vary depending on the time of year that planting takes place. Native seeds can also be applied in hydromulch. Many of the native species are difficult to source and have low germination rates. Consultation with seed merchants to discuss available species and how to treat them to achieve good germination is advised.
vi. Fertiliser
The type and rate of fertiliser used should be varied to suit the soil type onsite and the variety of seed specified. For grass type vegetation we recommend 250kg to 400kg per ha. When using some native seed, organic fertiliser should be used.
Post-Hydromulching Maintenance
During hydromulching water will soften the seedcoat, which begins the germination process. The seed should not be allowed to let out to dry out after initial watering. It is vital that post installation watering takes place. Application rates should be varied to suit local conditions. Generally, watering should take place every day until germination and then gradually reduced to harden off the plants.
Typical Hydromulching Specifications
For relatively flat areas with little overland flow
Type A
| Mulch | Recycled paper 100% |
| Application Rate | 1,500kg/ha |
| Tackifier | 3% By weight |
| Water | 35,000ltrs to 45,000ltrs/ha |
| Seed Mix | Site specific |
| Fertiliser | Site specific |
Type B
| Mulch | Sugarcane Mulch 75% Recycled Paper 25% |
| Application Rate | 2,500kg/ha |
| Tackifier | 3% By weight |
| Water | 55,000ltrs to 70,000ltrs/ha |
| Seed Mix | Site specific |
| Fertiliser | Site specific |
Batter Slopes to 1:3 Gradient
Type A
| Mulch | Sugarcane Mulch 65% Recycled Paper 15% Wood Fibre 20% |
| Application Rate | 3,000kg/ha |
| Tackifier | 4% By weight |
| Water | 55,000ltrs to 70,000ltrs/ha |
| Seed Mix | Site specific |
| Fertiliser | Site specific |
Type B
| Mulch | Sugarcane Mulch 75% Recycled Paper 25% |
| Application Rate | 3,000kg/ha |
| Tackifier | 4% By weight |
| Water | 55,000ltrs to 70,000ltrs/ha |
| Seed Mix | Site specific |
| Fertiliser | Site specific |
Steep Batter Slopes over 1:3
| Mulch | Sugarcane Mulch 65% Recycled Paper 15% Wood Fibre 20% |
| Application Rate | 5,000kg/ha |
| Tackifier | 5% By weight |
| Water | 70,000ltrs to 85,000ltrs/ha |
| Seed Mix | Site specific |
| Fertiliser | Site specific |
Note! These specifications are a guide only. For more specific information please contact Erosion Solutions International Pty Ltd. on 61-7-3114 8230