Weeding Out Better Wines

The nation's agriculture relies a good deal on its clean reputation. Thelack of residual pesticides, herbicides and other pollutants has givenAustralia's food a high international standing, and a very valuable onecommercially.

It's a reputation that needs constant vigilance. As Australianproducers are increasingly aware, one contamination scare would do theirfood export trade a great deal of damage. In the wine industry, itcould be devastating.

Already, a giant UK supermarket chain is questioning Australia's biggestwine producers about their use of herbicides that are known tocontaminate ground water. Their wines are tested for such contaminantscontinually, but even anecdotal evidence of such herbicide use couldcause significant damage to exports.

In that climate, alternatives to chemical pest control appear veryattractive. Mr Chris Penfold, a Research Officer with AdelaideUniversity’s Department of Agronomy & Farming Systems at the Roseworthycampus is about to begin a comprehensive study of organic weed controlin vineyards.

Funded by the Grape and Wine Research and Development Corporation, andsupported by several local industries and a Californian equipmentsupplier, the project should produce valuable information on how tocontrol vineyard weeds without the use of chemicals. "Not all weeds are bad," says Mr Penfold, "but some might introducedisease to the vines, or act as habitat for insect and other pests. Mostly they simply compete with the crop."

A number of weed control measures will be trialled, he says.

"Cultivation is an obvious one, but cultivation can cause problems bybreaking down the structure of the soil and exposing it to wind andwater erosion. We will be looking at carefully timed cultivation withdifferent implements, along with several other techniques."

These include "flame weeding", where a tractor-mounted device, fuelledby gas, heats the weeds to the point where their cell walls rupture. The use of flame weeding depends on the weed species present andmanagement aims. The gas supplier, Kleenheat, will supply gas andequipment for these trials.

Mr Penfold will also investigate mulching vines, but even that techniquehas variables that must be tested separately.

"There has been quite a bit done already on mulching," says Mr Penfold,"but mainly to improve vine vigour and productivity while simultaneouslyreducing evaporation losses. Now we will see what it can do for weedcontrol.

"Cereal straw mulch has commonly been used on vines, but as itdecomposes it can compromise nitrogen availability. Other concerns arethat it provides a habitat for mice, which then attracts snakes andendangers vineyard workers," he says.

The project will experiment with compost mulching, using mulch donatedby Jeffries Soils and Peat’s Soil.

As well as tending their vines, vineyard managers must also deal withthe 70% of vineyard space that lies between the vine rows. These areasrequire treatments different from those applied to the rows.

"Some weeds in these areas can even be beneficial," says Mr Penfold. "They may help to fix nitrogen in the soil, soak up surplus water oreven provide a habitat for predatory insects that prey on pest insectspecies and reduce their numbers."

The project will begin in the new year. Mr Penfold hopes that it willmake a significant contribution to agricultural practice.

"In the long term, vineyard managers will need to have alternatives toherbicides in controlling weeds, and for organic growers, a wider rangeof strategies than are currently available will enhance the value oftheir production systems," he says.