Want to use less herbicides?

Top: Twin fluid nozzies give effective applications at only 2 to 5 litres per hectare. Bottom: Ultra-low herbicide delivery - interim aim is 10 to 40 litres per hectare at 40km per hour.

A research and development team based in Victoria has developed a breakthrough in the conservative delivery of herbicides. The so-called 'Spraysmart' system involves new hand-held of field sprayers designed to safely deliver herbicides at very low volume rates without unduly changing potential droplet drift.

The system includes reccommendations on a range of complementary herbicides covering the major weed complexes. The sprayer design revolves around adaptation of a twin fluid nozzle.

The payback is hoth environmental and crop benefits and considerable financial savings for farmers and other users.

According to project coordinator Harry Combellack of the Victorian Department of Conservation and Natural Resources Keith Turnbull Research Institute, the main criteria for the system were that it be simple to operate and reliable each time out.

Unfortunately Spraysmart, developed with financial assistance from growers through the GRDC, has now reached a Catch 22 situation. Mr Combellack said agrochemical companies are proving reluctant to undertake field trails and registration required to market products with suitable label recommendations until the equipment for their application is marketed.

Similarly, agricultural machinery manufacturers, although very interested, want to see registration and labelling of suitable herbicides for use in the 'Spraysmart ' system before they embark on the expensive path of converting prototype to commercial equipment.

The research team is turning to growers for help. Mr Combellack said he is,hitting the road as part of an extension program to inform growers of the benefits of the system and to encourage them to lobby for commercialisation.


Farmers and conservationists generally agree that a reduction in herbicide use benefits the whole community. Cerealgrowers alone spend an estimated $319 million dollars on herbicides each year, and spend another $40 million dollars or so applying them.

While herbicides provide undeniably effective, energy-effective control of weeds and make a significant contribution to strategies aimed at reducing soil degradation they present a growing list of worries. Those include concern that they may affect human health by direct contamination or through residues in air, food or water.

Experience is also showing some herbicides may have adverse affects on crops by fostering root diseases in wheat and barley grown on calcareous soils and in lupins. Research is also indicating that plant nutrition may be adversely affected hy the use of some herbicides (see Ground Cover issue 1).

Overseas governments have been working towards reducing their use. Denmark introduced laws in the late 1980s aimed at reducing herbicide use by 25 per cent in three years and by 50 per cent in 10 years. Sweden, Holland and parts of Canada have already followed suit.

Effective control at 1/3 the rate

Research overseas has shown that some herbicides, especially when mixed with oil adjuvants, can control weeds effectively at rates as low as one-third those normally used. But currently available commercial machinery cannot readily apply chemicals evenly at such low rates.

The redesign of application equipment was therefore basic to any significant changes.

The Australian team coordinated by Mr Combellack took up the challenge. The team comprises Australian and overseas representatives of spray-machinery manufacturers, agrochemical companies, market researchers and government, farmer and research organisations.

They envisage volume rates eventually falling as low as 2 litres per hectare and a reduction in herbicide use rates of about 15 per cent. They have set an interim goal of 10 to 40 Iitres per ha at 10km per hour.

Other goals included the development and registration of new herbicides and adjuvants to take advantage of the new equipment, together with protocols for their safe use and handling. Ideally, said Mr Combellack, the chemicals will be delivered in a ready-to-use form.

Enter the twin fluid nozzle

The twin nuid nozzle has proven the key to effective applications at rates as low as only 2 to 5 litre per ha. The nozzles have been used in industry for several decades but not for this purpose. Researchers have successfully designed prototype hand-held application equipment and a prototype field sprayer that can relate output to ground speed and apply herbicides without greatly increasing droplet drift. The sprayers are simple to operate and can be used on light-weight vehicles.

The success of the nozzles depends on their ability to atomise liquid at low rates of flow - less than 100mL per minute - by mixing it with compressed air internally.

Growers should take advantage

"Growers made this research possible through the Grains Research and Development Corporation, and the results can repay that investment many times over," said Mr Combellack.

"If you want to help the environment and take advantage of financial savings the 'Spraysmart' system can offer, pass on the message to the agrochemical and machinery companies through your local representatives. If we can convince them that the market lies ready and waiting, we can break the log-jam"