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I received my first call from Joe, a Morinville-area farmer who farms 2,000 acres of canola and wheat, on May 28, 2012. Concerned with the level of scentless chamomile in his canola field, Joe was looking for a way to clean it up. He had planted glyphosate-tolerant canola on this particular field, but by late May, Joe noticed the chamomile had taken over his field.

Given that the canola had been planted, but had not yet emerged, I suggested that he spray an herbicide containing clopyralid and glyphosate on the field. Twelve days later, Joe and I checked the efficacy of the chemical on the weeds. To our dismay, the herbicide had done little to set the chamomile back. At the time of application the weeds had already grown too big.

A week later, Joe called again. “The chamomile is choking out the crop and reducing emergence,” he told me. I had a feeling there was more to this field than met the eye, so I decided to visit Joe’s farm again.

Although some of the smaller weeds looked stunted from the herbicide application, the larger ones were still going strong. A thorough investigation revealed that the field was not uniform and had many low spots and inconsistencies to the soil. The areas of poor emergence did not correlate with those being choked out by the chamomile. Where there were higher incidences of weeds there did not appear to be fewer canola seedlings.

We first thought that nutrients had leached from the affected areas, or excessive amounts of water had drowned the cotyledons in low-lying regions; however, we quickly realized that the germination pattern did not correlate to those areas where nutrients had been abundant or water had been excessive. Frequent bare spots occurred randomly in the field.

It had not been dry enough to cause fertilizer to burn the seed. However, continued scouting of the field revealed the cotyledons that had managed to push through the soil looked healthy, but many of the seeds that had germinated had died off before they emerged from the soil.

Records indicated temperatures over that period would not have caused frost damage. There had to be something else going on here. The only thing that made any sense at this point was a problem with the soil.

“What did you have here last year?” I asked Joe.

“This is my first year with the field, and I don’t know what the previous renter had,” he told me.

To diagnose this problem, the field’s history was crucial.

What is causing the poor emergence of crop in this field? Send your diagnosis to Grainews, Box 9800, Winnipeg, MB, R3C 3K7; email [email protected] or fax 204-944-5416 c/o Crop Advisor’s Casebook. Best suggestions will be pooled and one winner will be drawn for a chance to win a Grainews cap and a one-year subscription to the magazine. The best answer, along with the reasoning which solved the mystery, will appear in the next Crop Advisor’s Solution File. †

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