The benefits of rotation may apply not only to herbicides and crops but also to varieties, say agronomists.
“In reality, some producers, especially in southern Alberta’s feedlot regions, have few choices from their current barley-snow rotation,” said Kelly Turkington, a plant pathologist with Agriculture Canada in Lacombe, Alta.
“They need feed barley or silage or both. And barley gives them that,” he said.
That can create disease problems but rotating varieties with differing sources of resistance can help, said Neil Harker, also with Agriculture Canada in Lacombe.
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“It is even better if you can add an oats and triticale to the rotation, but even differing barley varieties will help a great deal. It all adds diversity to the soil and that helps to naturally avoid serious disease problems,” said Harker.
Some researchers say it is no accident that net blotch and scald have become a greater problem in some regions of Alberta than in other parts of the Prairies.
The “snow-barley rotation” often has depended on saved seed, with single varieties being replanted year after year on the same land. The increased water retention in minimum and zero-till systems means that not even summerfallow breaks the continuous barley cycle.
“There is a million acres of barley silage out there every year in Alberta, many more in feed barley, and it is eliminating the (microbial) diversity in the system,” said Harker.
Turkington said fungicide applications may help, but are poorly studied, expensive and none is a “magic bullet.”
After three seasons of experiments at Lacombe, the interim results are convincing scientists that changing varieties every year may allow producers to avoid disease problems that would force them to change crops and feeding rations.
Research is showing that choosing not only a different variety of barley, but also one from a different breeding program can make a significant difference.
“Switch from a CDC (University of Saskatchewan Crop Development Centre) variety to an AC (Agriculture Canada) variety and the change in cultivars make a significant break in the disease chain,” said Turkington.
George Clayton, deputy science director at Agriculture Canada in Lacombe, agreed.
“Kasota, Seebe, Lacombe and Falcon, some have the same genetic background for disease resistance, so you need to pinpoint that background in order to make the best choices for what to include in a rotation,” he said.
Harker said the most effective rotational change is still switching crop types.
“The biggest bang for your buck remains in changing crops. We see yield increases, not just a drop in disease issues, when we make that triticale, oats and barley rotation. But making a variety change improves soil diversity and for some producers that may be enough for now,” he said.
