Mechanical clearing of gorse

01-02-2009 | Not Specified

Mechanical clearing is an effective primary control method in some situations.

However some gorse grows back from stumps and roots left behind after clearing.

Clearing using this method won't reliably kill mature gorse, so you must combine it with other methods to achieve long-term gorse control on your property.

The aim of mechanical clearing is to reduce the above ground mass of gorse before follow up methods are applied; including spraying with herbicides, restoring pasture, grazing or cultivation.

Typically, spraying re-growth after mechanical clearing requires only 20-25% of the herbicide needed for spraying uncleared gorse.

A variety of mechanical clearing techniques are proven on gorse.

If you clear with mechanical methods it is important to remember that the use of heavy machinery can increase the risk of erosion and soil structure degradation.

Larger machines generally work faster and may be more cost effective. Proven techniques are summarised below.

• Dozing: with a bulldozer, tractor with blade, or similar machine.

The aim of using a bladed machine is to break the gorse off at soil level. Avoid scalping the surface soil.

Grubbing with an excavator, tractor with bucket, front-end loader, bobcat or similar machine. The aim is to break the gorse off at soil level without scalping the soil.

This is most effective on old, hard gorse and least effective on young, soft gorse.

• Root raking or stick raking: with an excavator or bulldozer fitted with a root rake or stick rake.

The aim is to pull bushes and larger roots out of the ground.

This method results in less re-growth than dozing, but creates more soil disturbance, therefore more seedling re-emergence.

• Mulching or grooming: with a tractor or excavator-mounted mulcher.

This method cuts bushes off at ground level and processes them into mulch. The mulch layer provides some suppression of seedlings. Excavator mounted mulchers can be used to access creek banks and steep sites, but must be kept out of the streambed proper (see p52).

• Crushing: with a tractor or bulldozer mounted or similar.

This method breaks bushes, including the root crown, into pieces and incorporates broken material with the top 10cm of the soil profile.

This is claimed to result in less re-growth than other mechanical methods because the leaves and green stems are buried.

• Slashing: with roadside or grass slashing equipment can be used to reduce the height of gorse.

Slashing will not kill gorse, and gorse subject to repeated slashing will flower and set seed at a height of only 10-15cm. It may also develop an extensive root system.

The reduced stem and leaf growth means that there is not enough surface area to absorb sufficient herbicide for effective follow-up spraying.

The deep trash layer left after slashing gorse limits effective herbicide coverage when spraying re-growth or seedlings.

• Pulling: with a tractor and chain or similar tools.

This can be effective at reducing above-ground mass. Pulling should not be used where soil disturbance is unacceptable, especially in riparian zones.

• Cultivation: with discs or similar equipment.

This is useful for breaking established roots and for follow-up treatment of seedlings and small re-growth. Some equipment may be strong enough to clean up burnt canes after fire.

Ploughing living gorse is not deemed to be practical. Trying to cultivate standing bushes will create a mess and might damage equipment.

Cultivation as part of a cropping regime or for pasture maintenance is very effective at killing gorse seedlings. This buries seed below viable depth and can also promote germination prior to other follow-up methods.

Many farmers believe that three to four years of cultivation and cropping will control gorse effectively on arable land.

Any machinery or implement used to control gorse must be thoroughly cleaned before leaving the infected area to prevent the spread of gorse seed.

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