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oe owns a 2,000-acre farm near Morinville, Alta., where he grows canola and wheat. In May 2012, Joe called me with concerns about the level of scentless chamomile growing in his canola field. I suggested he spray an herbicide containing clopyralid and glyphosate; however, 12 days later when we scouted for chemical efficacy we found the herbicide had done little to control the outbreak. A week later, Joe called me again. He thought the chamomile was choking out his canola crop.

At the field, the patterns of poor emergence did not correlate with the areas being choked out by the chamomile. In the areas where there were higher incidences of weeds, there did not appear to be fewer cotyledons. We thought nutrients had leached in the soil profile in the damaged areas, or excessive amounts of water had drowned the cotyledons in low-lying regions; however, we realized that the germination pattern did not correlate to areas where nutrients had been abundant, or where soil moisture had been excessive.

There were many seeds that had germinated but died off before emergence. There had to be something wrong with the soil, I thought.

I asked Joe what he had planted the previous year, but Joe didn’t know — this was his first year with this field and he did not know what the previous tenant had planted.

In cases like these, the history of the field is all-important. Joe contacted the previous tenant to find that he had planted aherbicide-tolerant canola, and a Group 2 herbicide had been the chemical of choice. Joe’s canola was suffering from herbicide injury from residue in the soil!

Now Joe had a tough decision to make; reseeding the field to a cereal was the only option left — that residue wasn’t going anywhere. However, Joe decided against this option because he felt the field was not ideal to begin with.

This time, the casebook does not have a happy ending. Very few canola plants grew in the field, resulting in drastically reduced yield results.

Understanding the field’s history when taking on new acres is critical to success. Questions need to be asked and answered in order for a new tenant to determine an appropriate crop rotation schedule for a field. †

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