Cotton into wheat: less erosion and pesticide run off by Cathy Nicoll

Cotton conventionally sown (top) and direct-drilled into wheat stubble.

Planting cotton into wheat stubble has been shown to reduce by as much as 70 per cent the amount of soil (and pesticides) lost from paddocks during irrigation.

The innovative research by the Queensland Department of Natural Resources (QDNR) at Emerald also proved the additional benefit to growers of a reduced need for early-season pesticide sprays, with no reduction in cotton yield.

QDNR scientist David Waters is enthusiastic about the results. "This is the first time this cropping technique has been tried with such success.

"It shows that it is possible to double-crop cotton into wheat stubble. We expect even less soil loss next season. The growers will trial shielded sprays rather than use inter-row cultivation to control weeds later in the season." (Shielded sprays have a collar that prevents spray directed onto weeds in channels from drifting onto nearby cotton plants.)

The Land and Water Resources Research and Development Corporation, the Cotton Research and Development Corporation and the Murray-Darling Basin Commission jointly funded the research.

The one-year study compared erosion and pesticide loss from paddocks used to grow cotton conventionally and a wheat-double cotton crop. The trials were based on two adjacent properties in the Emerald Irrigation Area in Central Queensland.

Fewer pests

Mr Waters said that researchers and growers alike found fewer problems with insects and weeds in paddocks with cotton sown into the wheat stubble. The result was a decrease by 40 per cent in the total amount of endosulfan needed to control heliothis.

"This may be because the stubble provided a physical barrier against heliothis invasion while the cotton plants were young," he said.

Grower Scott Black of 'Liskard' is particularly happy with the results. "We've saved on erosion. We've saved on chemicals. We've saved on wind damage in November. And the wheat pays for itself."

The only drawback, according to Mr Black, was slightly reduced establishment for cotton when sown directly into stubble. Even so, total cotton yields were about the same as the conventional cotton crop at around six bales per hectare.

"It's only a minor problem, and I think we'll have it sorted out this year," says Mr Black. "I will continue to crop wheat over the winter, just for its stubble. Having the wheat stubble meant the cotton needed three less endosulfan sprays, with no reduction in yield. I think anyone would be happy about this type of result."

Mr Waters expects similar reductions in soil erosion in dryland cotton enterprises. But dryland wheat does not produce enough stubble to protect young cotton plants from pests, and so growers would not see the same reduction in endosulfan spray applications.

Contact: Mr David Waters 07 4982 8800 Mr Scott Black 07 4982 0592

Region North