Growers who control summer weeds reap productivity benefits

SOUTHERN grain growers are being advised to control summer weeds early to reap agronomic and financial benefits.

Timing is everything: Herbicides are most effective when summer weeds are small and actively growing.

SOUTHERN grain growers are being advised to control summer weeds early to reap agronomic and financial benefits.

According to the Grains Research and Development Corporation, early summer weed management can boost water use efficiency, crop establishment and yields, herbicide efficacy, pest and disease control, nutrient availability and overall grower profitability.

The GRDC’s landmark National Water Use Efficiency Initiative showed spraying 10 days after significant rainfall resulted in the greatest subsequent winter crop yield across 300-700mm annual rainfall areas when compared with late summer weed control and no control at all.

In areas where ground cover was minimal following significant rainfall deficits and failed crops, growers were advised to consider the risks of removing any existing vegetation too early.

Agricultural scientist and key researcher leading the WUE Initiative James Hunt said he encouraged growers to manage summer weeds at the three to five leaf stage using herbicides at registered label rates, as herbicide efficacy was highest when summer weeds were young and actively growing.

He said summer weed control replicated experiments conducted during the WUE Initiative demonstrated average yield improvements in winter crop performance of 60 per cent.

“In seasons with high growing season rainfall, yield improvement was driven by nitrogen availability and in seasons with low growing season rainfall it was driven by water availability alone,” Dr Hunt said.

“In average seasons it was driven by both nitrogen and water availability.”

Dr Hunt said a further benefit of summer weed control was destruction of the green bridge (weeds and volunteer cereals) that can harbour pests and diseases between seasons, potentially reducing winter crop performance.

Growers were also being reminded to follow best practice when spraying summer weeds to reduce the risk of off-target spray drift and to be aware of new restrictions to the use of 2,4-D.

The Australian Pesticides and Veterinary Medicines Authority has suspended the labels of all products containing the active ingredient 2,4-D from October 4, replacing them with a permit.