Research done across Saskatchewan recommends that the best way to optimize wheat yields is to adjust your wheat seeding rate to reflect moisture conditions, says a report from the Western Applied Research Corporation (WARC).
The research concluded if you’re heading into what looks like a drier growing season, a mid- to lower wheat seeding rate achieves the optimum yield — and if it looks like decent soil moisture for the growing season, go with a higher seeding rate.
The research project, launched in 2022, was in response to what appears to be a cycle of drier growing seasons, WARC research manager Jessica Enns says.
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“Some producers were asking if the standard provincial recommendation for wheat seeding rates should be adjusted due to the dry weather,” she says.
Saskatchewan Agriculture has a standard recommendation that producers target between 20 and 25 wheat plants per square foot — but do those figures hold up under varying moisture conditions?
The project kicked off in 2022, with Blaine and Adam Davey Farms, Holman Farming Group and Kun Farm Inc. covering the cost of the WARC research at two sites. Sask Wheat in 2023 funded the second year of an expanded project carried out at eight sites, including Prince Albert, Melfort, Yorkton, Indian Head, Swift Current and Scott.
What did they learn?
For optimum wheat yields at sites with lower moisture — Scott, Indian Head and Melfort — the ideal seeding rate targeted a plant count of between 15 and 25 wheat plants per square foot, for an average of 20 plants per square foot.
Under higher moisture growing conditions, meanwhile, such as at Swift Current, Prince Albert and Yorkton, the ideal seeding rate showed a plant count between 25 and 35 plants or an average of at least 30 plants per square foot produced optimum yields.
The WARC research project used seven different seeding rates at all sites. Treatments included:
- 108 seeds/square metre, resulting in 10 plants per square foot
- 163 seeds/square metre, resulting in 15 plants per square foot
- 217 seeds/square metre, resulting in 20 plants per square foot
- 272 seeds/square metre, resulting in 25 plants per square foot
- 326 seeds/square metre, resulting in 30 plants per square foot
- 378 seeds/square metre, resulting in 35 plants per square foot
- 432 seeds/square metre, resulting in 40 plants per square foot
To determine high and low moisture areas, they looked at the growing season precipitation for both 2022 and 2023 and calculated what percentage that was compared to the long-term average.
“Those sites where the growing season moisture was below 70 per cent of the long-term average were described as the low-moisture group, while sites with moisture greater than 70 per cent of the long-term average were placed in the high-moisture group,” Enns says.
Among the low group, Indian Head had the lowest precipitation at 49 per cent of long-term average, followed by Melfort at 56 per cent and Scott right at 70 per cent.
Swift Current wouldn’t generally be considered a high-moisture growing area, but in 2022 and 2023 it just happened to have higher growing-season moisture, which placed it in the high-moisture group — those two years came in at 99 and 110 per cent of the long-term average, respectively. Yorkton squeaked in with moisture at 72 per cent of long-term average, and Prince Albert at 81 per cent.
Hard red spring wheat varieties for the research project were selected based on popular varieties for each region. At Scott and Indian Head, the project seeded AAC Wheatland; at Melfort it was AAC Starbuck; at Prince Albert, AAC Brandon; at Swift Current, CDC Adamant VB; and at Yorkton, AAC Alida VB.
To determine the performance of each wheat plot, they looked at yield as well as head density, tillering, head size and length. “We looked at a number of factors to determine what seeding rate delivered the biggest bang for the buck,” Enns says.
Among low-moisture sites, the data showed the optimum plant count was in the 15-25 plants per square foot range; there was an average of 55 seed heads per square foot and between one and two tillers per plant.
“At the higher seeding rate on these low moisture sites the overall performance began to decline once the plots passed that 25 plant count, so on average 20 plants per square foot was optimum,” Enns says.
And among the research plots at high moisture sites, a plant stand of 25-35 plants per square foot (average of 30 plants), producing between one and two tillers, had the highest head densities and the highest yields. With higher moisture and higher seeding rates, the yields actually just kept climbing.
Researchers found with both low- and high-moisture groups using a seeding rate that produced between one and two tillers per plant was optimum. In plots with more tillering — more competition — yields were reduced. They also found with both low- and high-moisture sites, as yields increased, grain protein levels declined.
“We don’t have a specific moisture number, but these results suggest if conditions are dry at seeding and it appears to be a dry growing season ahead, opt for the lower plant count,” Enns says.
“And if it looks like fairly good moisture for the growing season opt for the higher seeding rate and plant count.”
As of March, WARC did not have plans to repeat the wheat seeding rate research in 2024.
