Choosing the right seeding rate for spring cereal crops is an important consideration for farmers looking for yield results that can maximize the return on their seeding dollars. A dense, uniform plant stand increases the crop’s yield potential, not only by reducing weed competition but also by compensating for plants lost to disease, insects and untimely spring frosts.
There are provincial guidelines to help Prairie cereal producers determine the best seeding rates to achieve target plant stands that maximize profitability. However, with new, higher-yielding cultivars supplanting older cereal varieties, could it be time to rethink those targets?
It’s a question Anne Kirk, a cereal specialist with Manitoba Agriculture, set out to answer with a series of seeding rate trials held in 2017 and 2018 and again in 2021. Her objective was to see if Manitoba Ag’s long-established guidelines for target plant populations needed to be adjusted to account for newer, high-yielding cultivars of spring wheat, oat and barley.
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Manitoba Agriculture currently recommends farmers use seeding rates that achieve the following plant stand targets — 23 to 28 plants per square foot for spring wheat, 18 to 23 plants per square foot for oat and 22 to 25 plants per square foot for barley.
“We wanted to see if producers … should stick with the recommendations we’ve laid out for a number of years, or if they would be more profitable by increasing target plant stands,” Kirk says.
The seeding rate trials were held at the Manitoba Agriculture Diversification Centres in Arborg, Carberry, Melita and Roblin, with James Frey, Scott Chalmers, Nirmal Hari and Haider Abbas assisting Kirk with the research.
A pair of cultivars for each crop were selected for the study — AAC Brandon and Prosper for spring wheat, CS Camden and AC Summit for oat and AAC Connect and CDC Austenson for barley. Kirk says two varieties were chosen for each of the three crops to determine if they responded the same way or differently to the various seeding rates.
The cultivars were planted to achieve target plant populations of 15, 21, 27, 33 and 39 plants per square foot, using seeding rates that were calculated using 1,000 kernel weight and an assumed seedling mortality rate of 15 per cent. For the 2021 trials, an extra target plant population category of nine plants per square foot was added.
Trial results
The oat and barley sites in 2017 and 2018 showed similar yields across a range of plant stands. At the wheat sites in 2017 and 2018, there was a general trend of higher yields with increased plant stand density, but no significant difference in yields between target plant stands of 21 to 39 plants per square foot at most of the sites.
The 2021 results were similar, showing no significant yield differences across the range of plant densities at most sites. There was a general trend of higher yields with higher-density plant stands at the wheat, barley and one of the oat sites, but no significant difference in yields between target plant stands of 21 to 39 plants per square foot at nine out of the 10 sites.
At all sites throughout the study, the two cultivars for each crop responded similarly in each plant population category, indicating similar seeding rate recommendations could be made for both varieties that were tested, Kirk notes.
“We found, in general, all of the varieties responded the same to the seeding rates,” says Kirk. “So, we couldn’t say (we’d) recommend a different seeding rate for, say, AAC Connect versus CDC Austenson.”
According to Kirk, a primary take-away from the study is there wasn’t anything to indicate Manitoba Ag’s plant stand target recommendations need to be adjusted, although she recommends farmers aim for plant stands on the higher end of the target plant stand recommendations.
Consider higher rates when seeding
There are times when farmers may have to put off seeding or possibly even reseed their spring wheat, oat and barley crops due to things like flooding, hail or herbicide injury.
Manitoba Agriculture cereal specialist Anne Kirk says in situations like this, upping seeding rates a little could be beneficial. As an example, she says it likely makes sense for a farmer needing to reseed spring wheat to select a seeding rate that corresponds with 28 plants per square foot (the upper end of Manitoba Ag’s recommended range for target plant stands for spring wheat), or even a bit higher.
“We know that with cereals in Manitoba, delaying seeding does reduce yield potential. In a late seeding or reseeding situation, I recommend increasing seeding rate,” Kirk says.
