by Deborah Jeanne Sergeant
Want a greater winter wheat yield? Dennis Pennington, wheat systems specialist with Michigan State Extension, offered numerous tips during his presentation “Precision Planting in Winter Wheat” at the recent Soybean and Small Grains Congress.
Pennington said he’s heard wheat growers who need to update their planter wonder if they should sell their drill, buy wheat plates and plant soybeans and wheat with the same planter. Row spacing plays into this decision.
“If we plant wheat on 15-inch row spacing, what impact will that have on yield?” Pennington asked. “Based on this, we ventured down the road on precision planting.” His research goal was to design a canopy structure to maximize the light interception and radiation use efficiency. Growers want a canopy that can capture as much light energy as possible and turn it into biomass. A number of things can influence wheat yield, like seed placement, row spacing, seeding rates, variety selection and planting time.
He said a conventional drill doesn’t allow for much precision. “You can calibrate to the number of seeds and seeds per acre, but dropping one by one, it can’t happen,” Pennington said. “An air seeder has the same concept.”
The goal is to be consistent. Uniform seed placement avoids variable planting depth, skipping and double planting. “We want a picket fence, like corn, but with wheat we have much higher populations than corn,” Pennington said. “We want uniform placing of the plants within the row and less gaps within the row. We think that by doing that, we might get a more uniform number of tillers per plant. That may lead to more uniform planting and more uniform heads and perhaps lead to things like better head scab control when we apply fungicide for fusariam head blight.” If wheat emerges more uniformly, then application of fungicide will be more effective since the plants will have uniform maturity.
His research project experimented with using a seed drill and a precision planter with 7.5-inch row spacing at two million seeds/acre and at one million seeds/acre. “By cutting the population in half, that space between the seeds is double,” Pennington said.
The trials took place in two locations in Michigan, where the climate is similar to that of the Northeast. The lower seeding rates were much more uniform in their planting depth.
“We measured the distance between these plants,” he said. “In an ideal world, it would be exactly the same down the row. You want the lowest coefficient variation as possible. The precision planter had lower, but it wasn’t statistically significant. Depth is another story.”
He measured all the plots and found that the variation was lower by 40% among those planted with a precision planter rather than the drill.
“With singulation, I don’t think they’re there yet,” Pennington said. “With depth control, it has a certain benefit.”
He wants to grow wheat plants with four to five first order tillers. “We don’t want second order tillers,” he added. “They form on tillers and don’t produce their own root systems. They usually are aborted and don’t contribute anyway.”
It’s also important to get the crop planted in autumn before winter dormancy. “At high seeding rates, we have a lot less heads per plant,” Pennington said. “The size of the heads on these low seeding rates are smaller because you have so many more heads that one root system is trying to support.”
The precision planter fields had more tillers over the season. “Both had more early in the season and both had tiller mortality and were harvested at about five,” Pennington said.
Ideally, he wants to see five tillers at the beginning of the season and to maintain them. The extra tillers use water and nutrients that don’t contribute to yield. Population has a significant influence on tiller development.
Farmers also have to look how their planting affects disease prevalence. Pennington collected samples and submitted them for testing for fusarium head blight. If fungicide is applied when plants were all flowering, it increases the treatment’s efficacy. That’s why a more uniform stand decreases fusarium head blight.
By lowering losses to head blight, farmers may be able to back off on their seeding rate. If the precision planter used different row spacing, that can also affect yield because it affects the canopy. Pennington found that five-inch row spacing is considerably better than other spacings.
“If you go to five-inch row spacing, you’ll gain 10 bushels per acre,” he said. “That is pretty significant. The narrow row spacing will improve yield.”
The number of seeds per acre also makes a difference. As population increases, the yield increases until you reach a certain plateau, Pennington explained. He found that 500,000 seeds/acre wasn’t enough, but between one and 1.5 million worked best of all the rates tried.
“Improved seed placement – seeding depth and spacing – at planting can lead to increase in crop uniformity and overall yield and quality,” Pennington said.
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