Like many no-tillers in North America, Australian no-tillers are concerned with the impact of changing climate and drought conditions. However, no-till and several other innovative ideas have helped the country’s wheat growers deal with reduced water supplies while boosting yields over the past 3 decades.
Besides making a shift to no-till, the first innovative idea was dealing with a water-limited yield factor. The goal is that about 18 pounds of wheat per acre should be produced for each 1 inch of water that the crop uses. At the time this goal was accepted by growers, wheat yields only averaged about half of this figure, says John Passioura, a honorary research fellow at the Commonwealth Scientific and Industrial Research Organization that serves as Australia’s national science agency.
New Crop Rotations
The second change was to introduce canola into the crop rotation. Where this was done, no-tillers found wheat yields were much greater following canola than with continuous wheat or rotating wheat with other crops.
No-tillers found the presence of canola roots in the soil sharply reduced the vigor of previously unrecognized root diseases. For years, several serious root diseases had led to unreliable responses to nitrogen.
The third change by Australian growers over the past few decades was a rapid shift to no-till and other conservation-tillage techniques. This was possible with the development of more effective herbicides that meant extensive tillage was no longer needed to kill weeds. As a result, no-tillers gained the confidence to aim for higher yields by making more effective use of fertilizer.
Overcoming The Drought
However, the adoption of these cropping practices ground to a halt when serious drought conditions occurred at the turn of the new century. But except for two very tough years, most no-tillers managed to harvest remarkably good yields by utilizing innovative management techniques.
While growers had long relied on the benefits of autumn rains to get crops off to a good start, climate changes resulted in more summer rains. By conserving more rainfall in the subsoil with more effective control of weeds, retaining the stubble from the previous year’s crop and doing a better job of capturing released nitrates, they were able to move to earlier planting.
This led to the use of slower-developing wheat varieties with much longer coleoptiles that can be no-tilled deeper to reach available moisture. However, it is important that these wheat varieties not flower until after the risk of frost damage had passed.
If crops can make more effective use of year-round rainfall, Passioura predicts wheat yields could rise by as much as 25% over the coming decade despite the recent volatility of weather patterns.