Features Cereals Seeding/Planting
In the cold, cold ground

A series of multi-site studies led by Brian Beres have shown that ultra-early seeding – seeding as soon as possible after the soil temperature first rises above freezing – does not compromise spring wheat yield. In fact, it improves yield stability and often increases yield, compared to seeding based on the calendar date.

Now, Beres is working on an ultra-early seeding system for durum wheat.

“On the Canadian Prairies, there has been a tradition of seeding based on the calendar date. For example, here in southern Alberta, the idea was that as long as wheat is planted by May 10, it’s fine because that’s the insurance cut-off,” says Beres, a research scientist with Agriculture and Agri-Food Canada (AAFC) in Lethbridge. “So there has been this adherence to arbitrary calendar dates as a guide for what would lead to the best outcomes for cereal production.

“I wanted to challenge that traditional thinking and see if we could develop a prescriptive practice that would tell us when we can seed, and if the field conditions allow us, then we go seed.”

Spring wheat results
Since 2015, Beres, his collaborators and Graham Collier, who worked on this research as a PhD student, have investigated spring wheat planting times that are triggered by the soil temperature, rather than the calendar date.

They used soil temperature measured at two inches (five centimetres) deep, and compared triggers ranging from zero through 10°C. The experiments took place at locations in Saskatchewan and Alberta as well as British Columbia’s Peace Region. They assessed the responses of CWRS, CWSWS, CPSR, CWSP and CNHR wheat varieties, and some cold-tolerant experimental lines.

They found that grain yield and yield stability were highest when planting occurs at soil temperatures of zero to two or 3°C. That holds true regardless of the wheat variety. And it holds true even if the planting date is as early as mid-February and bitterly cold conditions occur after planting. 

Beres explains that usually, at such early seeding dates, the seed will remain dormant – sometimes for more than 30 days – until it experiences the cues that govern when the plant initiates sprouting. However, sometimes a prolonged warm spell will enable the seed to germinate and emerge before below-freezing conditions return.

“Conventional wisdom would have said that’s a train wreck waiting to happen. But, after 40-plus site-years of experimentation, we have really never experienced any negative outcomes with ultra-early seeding,” he notes. “We now have an extensive depth of experience telling us anything over 0°C is your trigger to plant. Not only does seeding based on this trigger increase your yield stability field to field, year to year, but more often than not, you’re going to increase your yield too.”

Their results also show yield declines as the soil temperature trigger rises further, with the lowest yield from seeding based on the 10°C trigger.

In addition, they looked into other best management practices (BMPs) for ultra-early seeding of spring wheat. For instance, similar to Beres’ previous work, they observed that yield potential and stability are higher with a seeding rate of 40 seeds/sq. ft. (400 seeds/sq. mt.) compared to 20 seeds/sq. ft., and with a seeding depth of one inch compared to two inches. A fungicide-insecticide seed treatment is also critically important for increased resistance to the abiotic stress associated with this practice.

A pre-seeding burndown just before ultra-early seeding would not be an option since weeds won’t be actively growing at that time. However, Collier’s experiments show a fall-applied residual herbicide is an option. 

Furthermore, Beres notes, “These ultra-early systems are very competitive with weeds because of the early canopy closure. So, chances are that an in-crop herbicide will be sufficient.” He adds that you can consider ultra-early seeding as an opportunity to reduce your reliance on glyphosate, which could help slow the development of yet more glyphosate-resistant weeds.

The early advantage
The researchers’ calculations show this ultra-early seeding system provides a strong economic advantage. Based on Lethbridge data and 2019 CWRS prices, ultra-early seeding at zero to 2.5°C using high seeding rates would result in about $83/acre ($206/hectare) higher returns compared to seeding on May 1 (the traditional spring wheat planting date at Lethbridge) using lower seeding rates.

“In this ultra-early system, we’re using good varieties, good seedlots, dual seed treatments, a high seeding rate and an appropriate seeding depth. The reality is if you can string those practices together properly, you’re going to achieve yield potential a lot more easily and more often,” says Beres. “What we’ve shown in this research is that earlier is better.”

Several factors are likely involved in this earliness advantage. “One factor is that the plants are up and growing earlier in the season, which synchronizes much better to when photosynthetically active radiation is peaking on the Prairies, and also means an earlier harvest avoiding fall frost events,” says Beres. “So, we’ve got a canopy in place that enhances our light absorption and that’s all converting into yield potential as well as competitiveness with weeds.

“Another factor could be that ultra-early seeding disrupts some pest life cycles that a later-planted wheat could be more susceptible to.” For instance, ultra-early seeding might decrease impacts from problems like orange blossom wheat midge, wheat stem sawfly or fusarium head blight. 

“Also, earlier is generally better in terms of taking advantage of what spring moisture there is,” Beres adds. As well, earlier growth helps reduce the risk of yield impacts from drought and heat stress during grain fill.

Using a soil temperature trigger, rather than a calendar date, also allows growers to capitalize on long-term Prairie climate trends toward earlier starts to the growing season. According to Beres, an Alberta farmer who has been growing crops for years says he can plant six weeks earlier now than when he first started farming.

One situation where later planting might be better than ultra-early planting is when severely dry conditions occur early in the growing season.

“However, the years when ultra-early seeding doesn’t work are few and far between,” Beres says. “It makes more sense to adhere to a strategy that works eight or nine times out of 10, as opposed to being conservative because that one-in-10-year situation might hit this year. You pay way more of a price over the long term if you take that conservative route.”

In addition, in those occasional years when ultra-early seeding doesn’t work out, at least there is time to re-seed.

Ultra-early seeding for durum
With funding from the Saskatchewan Wheat Development Commission, Beres is now developing BMPs for ultra-early seeding of durum. His collaborators on this project include durum breeders Curtis Pozniak with the University of Saskatchewan and Yuefeng Ruan with AAFC-Swift Current. 

This project is taking place at five sites – Lethbridge-dryland, Lethbridge-irrigated, Indian Head, Saskatoon and Swift Current – and involves two experiments.

The first is assessing the responses to ultra-early seeding of five CWAD cultivars. Beres selected popular varieties representing a range of maturities, including CDC Defy, AAC Stronghold, AAC Donlow, AC Transcend and CDC Desire. The seeding triggers in this experiment are when the soil temperature in the top two inches reaches zero, two, four, six, eight and 10°C. 

The second experiment is evaluating the responses of CDC Defy, AAC Stronghold and AC Transcend to ultra-early seeding and dormant planting, at seeding depths of one inch and three inches. In this experiment, the soil temperature triggers for ultra-early seeding are zero to three, five, 7.5 and 10°C. The trigger for dormant planting is when the soil temperature in the top two inches first drops below 2°C in the fall.

Beres included dormant planting in experiment two because of producer interest. “As soon as you show that ultra-early planting at or above 0°C can work, right away some farmers start asking, ‘Would planting in the fall work?’ So, they keep me on my toes.”

Both experiments use a relatively high seeding rate of 45 seeds per square foot and a fungicide-insecticide seed treatment. Durum is seeded into the standing stubble of the preceding crop, which is canola at most of the sites, but spring wheat at Swift Current.

After some preliminary work in 2021, the project’s fieldwork started in fall 2021. The earliest planting dates for the dormant planting plots ranged from Nov. 5 (Saskatoon) to Dec. 3 (Swift Current) in 2021. The earliest planting dates for the ultra-early seeding plots ranged from Feb. 9 (Lethbridge-dryland) to May 4 (Indian Head) in 2022.

Highlights so far
The results from 2022 indicate ultra-early seeding also works for durum. “Planting durum as early as when the soil temperatures in the top two inches reached zero to 3°C generally provided higher and more stable grain yield, regardless of the cultivar,” says Beres. “Delaying planting until the soil temperature exceeded 6°C resulted in lower yield stability and lower yields.”

For instance, in experiment one, there was a 25 per cent yield reduction for the 10°C planting compared to the 2°C planting. The initial findings indicate dormant planting is riskier and lower
yielding. “Based on our results to date, you’re going to have one or two outcomes with dormant planting,” says Beres. “One possibility is a train wreck. The other is good crop establishment but with yield potential less than the ultra-early planting and similar to planting at 10°C.”

The dormant-planted plots at Swift Current had almost 100 per cent winterkill, while the other locations had acceptable survival.

In some years at some sites, the ultra-early planted seedlings germinate and emerge and then cold conditions return, but the crop still performs well in the end.

What durum genetics are best?
So far, CDC Defy has the highest overall yields across all the environments and planting dates. However, figuring out which durum genetics would be best for ultra-early seeding is still a work in progress.

Beres points out that in some situations, farmers might want to choose a very early-maturing variety so they could get the crop off as early as possible. That could open up opportunities to relay crop or to plant a fall-seeded crop or cover crop after the ultra-early seeded crop is harvested. Growing an earlier maturing variety could also help the crop avoid some drought and heat stress problems. And it could widen the harvest window so the farm’s workload is more spread out.

In other situations, farmers might prefer to select a much later-maturing variety than usual for their area so they can capture potential benefits from that, such as higher yields. 

Beres also sees an opportunity for breeders and seed developers to produce varieties that are specifically targeted for ultra-early seeding.

“For instance,” he asks, “could you develop a wheat that has some enhanced trait around abiotic stress resistance or some other trait that could be fully exploited or facilitated by ultra-early seeding?”

Tips for growers
“If you want to try ultra-early seeding, the biggest tip is to adhere to the prescriptive practice. The first time you observe soil temperatures in the top two inches exceeding 0°C, that’s when you go in if you can. That trigger has proven to be pretty reliable; don’t go in before you reach that trigger.”

Be sure the temperature probe is at two inches depth, just below where the seed will sit. A common practice is to check the soil temperature at 10 a.m. each day. Take the temperature at various places across the field to encompass the range of conditions, like low and high spots, so you have a representative sample.

Once you reach the temperature trigger, start planting as soon as field conditions will allow it. In the northern Prairies, consider selecting fields with good drainage for ultra-early seeding to reduce seeding delays due to excess moisture.

Using a dual fungicide-insecticide seed treatment to enhance plant resistance to abiotic stress is very important. Optimum seeding rates, good varieties and good seed quality are also prudent. 

Looking ahead
The fieldwork for Beres’s durum project is continuing in 2023 and finishes in 2024. Next, he hopes to tackle ultra-early seeding of barley because of the interest expressed by barley producers.

“Ultra-early seeding is about getting the crop’s photosynthetic machine built as early as you can because that is going to spin off all sorts of benefits,” says Beres. “The fact that we’ve got so many site-years of data with so many positive results tells us ultra-early seeding is worth exploring. It’s not a one-off; it’s a strategy that works.”