Hydroseeding a History

Hydroseeding is a method of spraying seeds on to large areas or steep slopes evenly.

Hydroseeding was developed in the United States where there was a need to establish grass on order to prevent soil erosion following the "Dust Bowls" of the 1930's. The process has developed over the years but the basics are still as true now as they were then.

What was required was a system that would fix seed to soils and increase moisture retention in order to encourage rapid growth. Various different mulches were tried and finally it was decided that wood based products offer the best in all situations. We at goroots now use only wood based products and our own wood peat mix.

Interestingly one of the develpoments tried and rejected was to mix the seed with tar emulsions which was used for sticking the seed in very difficult applications such as the high traffic areas of airport runways. We have used tar on a couple of projects but now due to the enviromental problems its use is severly restricted.

What goes in to the mix

The process involves 4 elements

1. Seed: Generally grass seed mixed in different proportions depending on the application. The rate of application depends on the use that the turf will be put to after establishment. From 20gms/m² for amenity applications to 30gms/m2 for fine turf. Using a variety of suppliers we are able to provide virtually any seed mix. We can also apply wild flowers and sedums if required though in these cases the application rate is much lower 5gms/m².

2. Mulch: There is a considerable range of Mulch types after much trial we have settled on 100% wood based Mulch this consists of tree fibres only. The main advantage is our mulch can be applied at much thicker rates than those containing paper there by allowing better germination we can apply at a rate of 3,000 kg/ha where as the paper and cotton waste are recommended above 800-1500kg/ha. The advantage of thicker mulch applications is the seed is better protected and much more of the moisture is retained. Paper mulches have very little use as they dry out very easily and form a crust that small plants are unable to penetrate.

3. Fertilizer: We use a fertilizer designed to promote germination and seedling development we also match the fertilizer to the prevailing ground conditions.

4. Tackifier: This is added to the mulch mix in order to increase the adhesion of the slurry as well as to allow for additional moisture retention. In a major study of hydroseeding the conclusion was that Wood mulch combined with tackifier provided the best possible outcome in all conditions tested.

What happens next

All the materials are mixed with water in a spefically designed machine these operate on two systems

Mechanical Agitation

Mechanically aggitated hydroseeding machines have an auger inside the which form two functions firstly to break up the bales of mulch and secondly to mix the slurry evenly. Mechanical machinesa are very efficient in this the best have paddles that continously move the material from one end of the machine to the other. Our machine can mix as fast as we can feel it.Evenly mixed mulch slurry is essentail for even applications also it means less hose blockages and less down time.

Jet Agitation

Jet agitated machines work using the main pump to circulate the slurry in order to mix it the usual design is to have a tube inside the tank with a number of holes in it, these create a swirling action within the tank whichencourages the mixing. There are two diasdvantages of this system firstly mixing is very slow and they will only realy work with the sub standard paper only mulch. Secondly they block up not only the hoses but the tubes with in the tank leading to long breakdowns. Often the operators well aware of these problems will reduce the mulch content in oredr to maintain output.