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Every year, landlord Dwan Jantz comes to her field
near Wilbur when the grain is being harvested.

Photo by William Bell




Distance learning

AMMO's 2020 Wheat College goes online with Wheat Pete

July 2020
By Trista Crossley

Setting aside the factors that can’t be changed, such as weather, what has the biggest impact on wheat yields? Peter Johnson, a Canadian agronomist with 30 years of specializing in cereals, says it’s all about the producer.

“Researchers have identified that if you put growers in the same region with the same inputs, everything the same, 27 percent, basically 1/4 of the yield outcome, is based on the producer and how they apply those inputs,” he said. “That is outside of the weather and soil type and everything else. It’s really cool in terms of how we can drive those yields forward, so keep an open mind.”

Johnson was speaking to growers as part of the Agricultural Marketing and Management Organization’s 2020 Wheat College. Normally, Wheat College is a full day of classroom and hands-on presentations. This year’s event, however, was solely online thanks to COVID-19 restrictions. Nearly 60 growers logged into Zoom to hear Johnson speak. Johnson is the resident agronomist with Real Agriculture, where he hosts a weekly podcast, “Wheat Pete’s Word.” He is also a regular on “Agronomy Monday” on Real Ag radio, Sirius Satellite Radio 147.

Johnson said the beauty of wheat is that the agronomy applies no matter where it is grown.

“If you think of it on a larger scale, a farmer’s No. 1 job really is harvesting sunlight. We take the sunlight energy, we take carbon dioxide, put it together with water, and we make photosynthate and turn that into food,” Johnson said. “I want to talk about how do we really make cereal yield? Wheat is different than many crops. It gives us so much more potential to do a good job of management, and it is way more management responsive. So where do we find those sweet spots?”

Johnson identified four areas for growers to consider:

• Number of heads per square foot. He said the simple answer is to use more seed, but it’s more important to manage tillering, particularly with a winter wheat crop. “Tillering is one of those things that we really haven’t paid enough attention to, the impact of tillering and how that plays in higher yields.” He encouraged growers to get out in their fields and actually count the number of heads in a square foot rather than just looking from the road.

• Number of spikelets or head size. “Lots of professors, wheat teachers will tell their students that the maximum yield of a wheat field is determined once we determine head size. Once we have that head size determined, we can’t do anything more to increase yield. I just call absolute malarkey to that.” Johnson believes there is much more to wheat yield than just the head size. In his experience, he added, almost never does head size limit wheat yield.

• Number of florets. Right after pollination is when it is determined if growers get one seed at every one of those spikelets or three seeds. “This is where a lot of us have slipped the clutch. We haven’t really thought about trying to manage at that stage, and yet, that is the No. 1 most critical period in terms of making higher wheat yields.”

• Weight of each grain. Johnson said growers can easily increase yields 10 percent just by having higher test weight in the crop.

“There are these critical times from a management standpoint where we need to be doing better,” he said. “How do we employ those various time periods and increase our yields if we can?”

Johnson said that growers need to better manage wheat during antithesis and grain fill.

“Grain fill conditions are critical. Once you hit anthesis, once that wheat head is pollinated, you have 1,200 growing degree days for grain fill. That’s a fairly constant number across most wheat. If we can figure out how to lengthen that grain fill at all, then we can get much bigger yields,” he explained.

Growing degree days are calculated by taking the high temperature plus the low temperature, divided by two, minus 32 to get the temperature in Fahrenheit. Then divide that number into 1,200. Johnson’s example was to take a high of 86 degrees and a low of 52 degrees to get 32 days of grain fill (86 plus 52 equals 138; divide that by 2; minus 32 is 37; now divide 1,200 by 37).

“If I could somehow shift that and get a 77 degree day and a 49 degree night, it’s not that big of a shift. When I do that math, I have a 39 day grain fill period. Does that make a difference on yield? That makes a huge difference on yield,” he said. “You gain almost four bushels per acre per day for every day extra of grain fill you can gain.”

The only way to do that, he added, was to plant earlier so the grain fill period is shifted into an earlier, cooler time of the year. Johnson cautioned that it isn’t a one-to-one ratio. One day of earlier planting doesn’t give wheat a day earlier to head out. As a cool season crop, a perfect day for wheat is a high of 65 with a low of 50 degrees. Johnson said if you could do that every day, you would maximize wheat yield. Wheat is comfortable with temperatures of 65 to 77 degrees. Temperatures more than 77 degrees will begin to negatively impact the crop, and if the temperatures go over 100 during the grain fill period, then the wheat crop is basically shut down.

“As you manage the wheat crop and you are trying to predict yields, keep those critical temperatures, 77 degree temperatures, in mind. Every day above 77 degrees during grain fill, you lose one bushel per acre per day,” he said.

Johnson also touched on keeping the crop green as long as possible by applying fungicides later during heading. He said research has shown that for every day the plant stays green through the grain fill period, growers gain up to three bushels per acre. He also stressed the importance of fall weed control, rotating crops and uniform emergence in a field by planting seed all at the same depth.

At the end of the presentation, Johnson answered growers’ questions about nitrogen application timing, the effect of nitrogen on protein and narrow row spacing and the role it plays in establishing a canopy. Besides providing an excellent means of weed control, a thick canopy captures more sunlight that in turn provides more yield.

“You can get high yields with wider rows,” Johnson said. “Just make sure there’s no bare dirt come flag leaf. If there is, you’ve left yield on the table.”

Johnson’s presentation can be found online here. Registered participants were entered into a drawing for a Blackstone Grill, which was won by Lori Stonecipher of Walla Walla, Wash. Ryan Ells of Toledo, Wash., was the winner of the RTIC Cooler from Corteva Agriscience.