Crop advisor casebook: Seeding issue makes for unhealthy wheat plants?

A Crop Advisor's Solution from the May 12, 2020 issue of Grainews

McKinna Kotyk.
photo: Supplied

In early June, I got a call from Keith, who owns a mixed cattle and grain farm near Grandview, Man. He’d been out checking his crop for herbicide timing when he noticed there were parallel stripes of yellowing plants running all across the field.

Keith, who also grows canola, oats and mixed hay on his 2,400-acre farm, thought it had to be an equipment-related issue, but he needed help figuring out exactly what that was.

“It seems clear that it’s a mechanical issue by the looks of the repetitive pattern,” Keith said, “but I’m not sure what the problem is.”

I told Keith I’d drive out to the farm to have a look. As I neared the wheat field, the striping pattern Keith was concerned about was clearly evident from a kilometre away, so I knew it was no small problem we were dealing with.

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When I entered the field, I observed that the affected plants all looked unhealthy, dull in colour, had spindly leaves and were slightly wilted. They were also smaller than they should have been at this stage in their development.

I asked Keith about the history of the field and was told it had been planted with a Roundup Ready canola variety the previous year. The grower also mentioned in the past few years he’d been growing large crops across his farm.

Initially, I wondered if the problem with the current year’s wheat crop could have been caused by some kind of sprayer malfunction during an early herbicide application in the field. However, a close inspection of the affected areas revealed no sprayer tracks and there were healthy weeds growing across the field as well.

My second thought was this could be a seeding issue. Keith informed me that he’d used a double shoot drill to seed the field, with phosphate accompanying the wheat seed in one shoot and another fertilizer blend placed away from seed with the other shoot.

I wondered if the seed had been placed deeper than it should have, and if this could explain the stark differences in plant size and vigour across the crop. This possibility was eliminated, though, when I dug up some plants in different parts of the field and observed the seed had been planted at the same depth in both affected and unaffected areas.

At this point, I knew there was really only one other possibility that could account for the problem in Keith’s wheat field.

Crop Advisor’s Solution: Mechanical problem causes phosphate deficiency in wheat

At this point, I started to lean toward the issue being a nutrient deficiency. Keith had informed me the field had produced a large crop for the last five years, which I knew could have led to a significant nutrient depletion in the soil.

Another clue presented itself when I learned Keith had applied two different fertilizer blends with the double shoot drill used to plant the crop, with phosphate accompanying the wheat seed in one shoot and a separate nitrogen, sulphur and potash blend was applied away from the seed as a side band.

When Keith informed me there was some phosphate left over after he finished seeding the field, I thought the most likely explanation was a mechanical problem with the seed-placed phosphate flowing properly during application in the affected areas. Keith acknowledged this was a possibility; this field was the last cereal crop he had seeded that spring, and he figured he’d been somewhat lax and hadn’t checked the drill for plugged openers or other issues prior to or while planting that last field.

To confirm the nutrient deficiency diagnosis, we collected some plant tissue samples and sent them in for testing, which later confirmed the affected plants were very low in phosphorus.

To address the issue, I recommended that Keith apply a foliar phosphate product. The undernourished wheat plants did recover slightly, although they remained a few days behind developmentally for the remainder of the growing season.

The result was that Keith’s wheat field yielded slightly less than what he’d hope for, but we were pleasantly surprised by the yield considering the symptoms of the crop in early June.

After harvest, fall soil samples were collected and they indicated that all of Keith’s fields were generally phosphate deficient, so I recommended that he adjust his fertilizer program to build phosphate levels across the farm. Keith assured me he would do that, and he would also be much more mindful of the importance of carefully checking his seeder and other equipment for potential problems, not just at the start but throughout the growing season.

McKinna Kotyk works for Richardson Pioneer Ltd. in Grandview, Man.

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