By Bruce Barker, P.Ag CanadianAgronomist.ca
Research over the past seven years has looked into the benefit of seeding spring wheat much earlier than is traditionally done. The theory was that ultra-early seeded spring wheat could produce greater grain yield by capturing the benefits of longer frost-free periods that include early season growing degree-day accumulation, increased vegetative growth periods, early season precipitation, increased day-length at anthesis and reduced average temperatures at grain fill.
Several research trials have been conducted since 2015 to look at the potential for seeding wheat as early as when the soil temperature reaches 0 C at the two-inch (five-cm) depth. One research study, led by Agriculture and Agri-Food Canada research scientist Brian Beres in Lethbridge, Alta, and Graham Collier, as part of his PhD research program.
The first study was conducted at six sites in Western Canada over four years from 2015 to 2018, with 13 total site-years: Dawson Creek, B.C.; Edmonton, and Lethbridge, Alta; and Regina, Scott and Swift Current, Sask.
Seeding date was based on soil temperature triggers of zero to 2.5, 5, 7.5 and 10 C. Two experimental, cold-tolerant, spring wheat lines, LQ1299A and LQ1315A, were seeded at 20 seeds/ft2 (200 seeds/m2) to represent a suboptimal rate and at 40 seeds/ft2 (400 seeds/m2) as the optimal seeding rate. The wheat was seeded directly into standing stubble at one or two inches (2.5 and five cm) deep with a no-till drill with knife openers on 9.5-inch (24-cm) row spacing. All seed was treated with a fungicide seed treatment to control common seedling diseases.
In all but one site-year, air temperatures below 0 C were recorded after the earliest seeding date with the lowest temperature of -10.2 C. Eight of 13 sites recorded air temperatures below -5 C after the initial seeding date with the lowest at -10.2 C at Lethbridge in 2016 and -9.8 C at Scott in 2016.
Similarly, all but one site-year experienced many days of air temperature below 0 C after the earliest seeding date, ranging from two days to a maximum of 37 days of frost after seeding. Eleven of 13 sites recorded more than 10 nights with air temperatures below 0C.
The highest average wheat yield at 74 bushels per acre (4.95 tonne/hectare) occurred with the earliest seeding date, while the latest seeding date at 10 C had the lowest average yield at 68 bu/ac (4.57 tonne/ha). Yield decreased linearly from the earliest to the latest seeding date. Seeding depth and wheat experimental line did not significantly affect grain yield.
The optimum seeding rate of 40 seeds/ft2 resulted in almost four bu/ac higher yield than the lower seeding rate of 20 seeds/ft2.
The greatest yield stability was due to combinations of optimum seeding rate, early planting, and to a lesser extent, shallow seeding depth.
The researchers calculated the economic benefit of ultra-early seeding at the optimum seeding rate compared to a traditional seeding date at Lethbridge on May 1 with a sub-optimal seeding rate. Seeding on May 1 was projected to result in an 11 per cent yield loss of 7.6 bu/ac (0.51 tonnes/ha). Using an average 2019 CWRS wheat price of $6.72/bu ($246/tonne) for 13.5 per cent protein wheat, ultra-early seeding at 40 seeds/ft2 would have generated an extra $83/acre ($206/ha).
Another research study by Beres and Collier investigated ultra-early spring wheat seeding using a conventional CWRS and two cold-tolerant spring wheat lines and seeding times based on soil temperature triggers of 0 C through 10 C. This research found that ultra-early seeding resulted in no detrimental effect on grain yield, and that it did not require the development of cold-tolerant spring wheat genetics.
A third research study assessed different spring wheat classes and varieties. This study found that all spring wheat varieties and classes tested, including CWRS, CWSWS, CPSR, CWSP, CNHR, and two experimental cold-tolerant varieties, maintained similar yields when planted at the 2 C or 8 C trigger planting temperatures. However, the ultra-early planting date had improved grain yield stability and improved growing system stability. This study was conducted at a sub-optimal planting rate of 20 seeds/ft2 (200 seeds/m2) in order to more easily identify any negative effect of ultra-early planting on conventional Canadian wheat lines.
The results of these studies show that adopting ultra-early wheat seeding systems on the Canadian Prairies can lead to higher, more stable yield, and that registered varieties in the spring wheat classes are suitable for ultra-early seeding.
The research found that the best agronomic practices are to seed wheat as soon as feasible after soil temperatures reach 0 C, and prior to soils reaching 7.5 to 10 C, with an optimal seeding rate of 40 seeds/ft2, and at a shallow seeding depth. Certainly, the opportunity to seed spring wheat at a 2 C temperature trigger requires well drained fields that allow early seeding to proceed, but the research highlights the potential.
Beres is now conducting research on ultra-early seeded durum wheat. Stay tuned for more results.
Bruce Barker divides his time between CanadianAgronomist.ca and as Western Field Editor for Top Crop Manager. CanadianAgronomist.ca translates research into agronomic knowledge that agronomists and farmers can use to grow better crops. Read the full Research Insight at CanadianAgronomist.ca.