Winter wheat at Lethbridge, Alta. has out-produced spring wheat by 20 per cent in Agriculture and Agri-Food Canada (AAFC) trials, and a quarter-century of follow-up work by Brian Beres now spells out the agronomic levers behind that gap.

The premium traces to escaping the July heat blast above 30 °C that triggers floret abortion in spring wheat. "Why does winter wheat around Lethbridge yield 20 per cent more than spring wheat?" asks Beres, a research scientist at AAFC Lethbridge. "It's because it avoids the typical heat and drought stress during its critical growth stage."

What seeding rate delivers a 20-plant stand?

Early trials at Lacombe and Lethbridge (2002-2004) found that the then-average farmer rate of 25 seeds per square foot (250/m²) routinely fell short of a 20-plants/ft² (200/m²) target. Forty-five seeds/ft² (450/m²) closed the gap reliably.

Above 300 seeds/m² rarely lifts yield further. The intangibles — weed competitiveness, uniform canopy, easier fungicide timing — justify the higher rate more than the raw tonnage does. Beres urges growers to adjust for thousand-kernel weight and environment rather than copy a single number.

Does a seed treatment pay?

A 2011-2013, 26 site-year Prairie study compared a low seeding rate plus no treatment against a high seeding rate plus a dual fungicide/insecticide seed treatment. Net returns clustered at C$148/ha (low rate + treatment), C$154/ha (high rate alone) and C$143/ha (high rate + treatment). The untreated low-rate system trailed.

The biggest surprise: abiotic stress tolerance, not pest control, drove most of the response when treatment was added. A stronger base agronomy plus a quality seed treatment sharpens system stability, Beres says.

How flexible is nitrogen timing?

Two multi-year trial series (2006-2010 and 2013-2018) tested side-banded urea, broadcast urea, urea-ammonium nitrate (UAN 28-0-0), Agrotain, SuperU and polymer-coated ESN. Most placement, timing and source combinations produced similar yields — except spring-broadcast ESN, where prills stranded in stubble thatch could not hydrolyse on cue.

Liquid UAN treated with a urease inhibitor, split 50-50 between side-band at seeding and in-crop at Feekes 4, held the highest, most stable yield with adequate protein. Enhanced-efficiency fertilisers did not cut greenhouse gas emissions. Early-spring broadcast untreated urea more than doubled N₂O loss versus side-banded urea.

Can winter wheat skip the in-crop herbicide?

Beres' 2018-2022 four-location Prairie weed project used AAC Wildfire hard red winter wheat. Pre-plant glyphosate, alone or tank-mixed with Focus (pyroxasulfone plus carfentrazone-ethyl), topped yields at 81 bu/ac (5.4 t/ha). The crop's competitive canopy removed the need for a spring in-crop spray, saving growers a combined $25/ac ($62/ha).

The same approach worked in canola stubble. A pre-harvest herbicide applied by a swather retrofitted with an on-board sprayer at 60 per cent seed colour change, combined with a pre-plant burn-off, killed the need for an in-crop winter wheat herbicide.

Beres credits the on-board sprayer concept to Jim Halford, an Indian Head, Sask. farmer and ConservaPak air drill inventor who demonstrated it on his own farm first.

Is a second fungicide pass worth it?

Within the same 2018-2022 project, two applications of prothioconazole plus tebuconazole (Prosaro XTR) at ZGS32 and ZGS60 hit 83 bu/ac (5.58 t/ha). A single ZGS60 pass reached 81 bu/ac (5.45 t/ha); the untreated check dropped to 78 bu/ac (5.25 t/ha).

"My takeaway from this research is that it yet again reaffirms that there is less reliance on herbicides in a winter wheat system, but one application of a fungicide is almost a pre-requisite in most environments and a second could be warranted if the penultimate leaf is showing signs of disease," Beres says.

Do plant growth regulators pay back?

Moddus (trinexapac-ethyl) trials on Flourish and Moats (2014-2017, multi-site) lifted grain yield 3-8 per cent and cut plant height 5-10 per cent. Plant height reduction was largest at Feekes 7 with the full dose.

Flourish, a short, stiff variety, showed no statistical response. Moats, a taller type with 'Fair' lodging rating, gained yield when Moddus went on at Feekes 7. Beres says the input pays only when lodging risk is real.

What stubble should winter wheat follow?

Across 16 site-years (2018-2022), straight-cut canola cut the following winter wheat yield versus windrowed canola. In the rotational-crop comparison, soybean stubble led at 59 bu/ac (3.94 t/ha), with lentil close behind; canola followed at 54 bu/ac (3.64 t/ha). Flax and oat trailed.

Beres calls the soybean-versus-canola result counter-intuitive: lower-residue pulses beat the snow-trapping champion. He still urges growers not to abandon canola, citing carry-over benefits beyond the first year.

What should growers pencil in next?

Beres frames the package as G × E × M — genetics, environment and management in combination. The EEF premium of $5-7/ac trades against yield-stability insurance, he argues; in higher-productivity zones, split nitrogen applications still pay.

Growers weighing next season's plan should benchmark 450 seeds/m² (adjusted to thousand-kernel weight) on a urease-inhibitor-protected UAN split, schedule at least one Prosaro XTR pass at ZGS60, and pencil in a soybean or lentil stubble ahead of the autumn drill.