Guenther: For problem fields, diagnosis in the details

Providing agronomists with detailed information on a problem field can help field visits go well — but farmers also need to know agronomists might not have a solution right away.

“Your job is to collect the information to help with the diagnostics. A lot of times you’ll want to guess at what it is, but stick to those facts,” Shawn Senko told agronomists during a recent Canola Council of Canada webinar.

Describe the problem

Senko, the council’s agronomy specialist for the northern Saskatchewan region, tries to get as much information as possible before going to the field.

He starts out by asking farmers what the problem is, where it’s showing up, and what it looks like.

Last year, for instance, Senko got several calls about aster yellows. After going through those first three questions, Senko was often able to diagnose the problem as aster yellows without visiting, though he did ask for pictures to confirm.

“So, that’s going to happen once in a while. You may get lucky and be able to solve the problem with these three questions,” he said.

Field history

Problems aren’t usually that easy to diagnose, so Senko’s next step is to get a fairly detailed history of the crop and field before going to the farm.

Farmers can help by tracking the crops grown on the field over the last three years. Senko says that helps him figure out potential disease pressures and volunteer issues.

Senko also likes to know which herbicides were applied this year and in previous years, and what rates were used. If farmers can’t remember which herbicides they used, knowing the previous varieties helps narrow the list.

Soil test results, including organic matter, pH levels and salinity, help agronomists figure out nutrient deficiencies and herbicide carryover potential.

Senko also gathers information from the current growing season. Seeding details, such as seeding size, date, rate, depth, source, variety and seed treatments, are useful. He also likes to know what types of seeding tool and packing system were used. Soil temperature and moisture during seeding give Senko an idea of expected emergence.

Senko also asks about fertilizer blend and placement. Most farmers will know the absolute numbers of N-P-K-S, but Senko also likes to know more details, such as whether it was all applied during seeding or split between spring and fall.

“A good example (is) sulfur source. I’ve had a field call in the past where I looked at the numbers. Everything looked good. Fifteen pounds of sulfur with the seed. It’s not a great amount, but it should be enough.”

Then, however, “I’m talking with our fertility expert, Dan, looking at all the information I took down. He said, ‘Well, wait, only half of that’s available the first year. So really that’s only like putting seven pounds down with the seed.'”

Farmers can also note weather conditions during the season, along with timing and uniformity of crop emergence.

Field observations

Once Senko arrives at the farm, he starts looking for patterns. For example, clear differences in emergence within a field could come down to something as simple as different seed lots.

Senko also looks at volunteers and related weeds at the field’s edge to get an idea of environmental stresses.

“You want to stay away from the trap of looking across the road at the neighbour’s field, though, comparing crops. Totally different seeding times, fertility, field history.”

Plant populations, both within a specific area and across the field, provide clues. Senko uses a plastic hoop to count plants at five to 10 sites in the field. He also eyes individual plants closely, noting:

  • Plant stage: This can help diagnose the problem later on.
  • Lesions: Colours, shapes, location on plant, size, how many plants have them.
  • Abnormal growth: Including stunted, twisted, wilted, or lodged plants. Senko compares them to unaffected plants.
  • Damage: Chews, rips, nips, broken stems. Does it look like insect damage?
  • Roots: Compare the roots of healthy and unhealthy plants.

It’s also worth digging in bare patches to see if there are cutworms, or whether seeds germinated. Senko also looks for a blue seed coat. Senko said he’s even found the seed coat in the previous year’s stubble, and it can help pinpoint problems.

Senko said one year he was checking a field where plants were dying a week after spraying.

“We started pulling plants and every one we find that’s dying doesn’t have a blue seed coat. And the healthy plants, almost every one has a blue seed coat with it.”

Senko said the farmer had used a different herbicide system with a previous canola crop, and the volunteers were dying. The current year’s canola formed a healthy plant stand.

The Canola Council also has an online diagnostic tool that farmers can use to come up with possible causes for problems in their canola crops.

— Lisa Guenther is a field editor for Grainews at Livelong, Sask. Follow her @LtoG on Twitter.

About the author

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Field Editor

Lisa Guenther

Lisa Guenther is field editor for Grainews based at Livelong, Sask. You can follow her on Twitter @LtoG.

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