Some of the wheat varieties that show an allelopathic effect are some of the most popular ones in the state, and are already growing in many fields right now. Lofton said if farmers know they planted one of the potential allelopathic wheat varieties, and they still want to rotate into winter canola this fall, they still have some options open to them.
“What we’ve seen in the greenhouse so far is that if we break down the residue through tillage or by burning, that essentially makes those chemicals less impactful,” he said. “Think about it. Those chemicals all secrete from the straw and dead material over time, with moisture and sunlight as it breaks down. Tillage or burning is a quick release of those chemicals, and helps move them out of the seeding zone in the field by the next time you seed canola.” Another method, for those who are really trying to stick to no-till, is to strip-till the field before canola, he said.
Lofton emphasizes that allelopathy is something that can be managed if farmers are concerned. First, they need to plant canola at the right time, and using good practices that will give the crop every advantage. Ensure that there’s proper seed-soil contact, and make sure that your fertility program is on point so that you don’t stress the plant out while it’s establishing itself. And, make sure the crop doesn’t have to further compete with weeds and diamondback moths as it’s growing later on.
Next, use the information OSU is providing as a tool to guide your rotations. There are nine wheats that have been identified to have varying impact on canola, he said. But, there are a large number of wheat varieties that don’t have an allelopathic impact as well. If you want to plant one of the wheats on the list that could be allelopathic, maybe use them in the years that wheat will follow wheat in your rotation, he advised.
“Finally, we have good information that some of the canola yield declines are only 10 to 15 percent in some instances,” he said. “If you’re okay with that, then plan for it and be aware. There might be a yield drag with canola following these certain varieties, but maybe you’re okay with 20-bushel canola versus 22-bushel.”