Fall-applied residual herbicides improve broadleaf weed management in ultra-early wheat (Triticum aestivum L.) production systems on the northern Great Plains

Abstract

Ultra-early spring wheat ( Triticum aestivum L.) planting systems based on soil temperature on the northern Great Plains have lower overall variability in grain yield, and can increase grain yield relative to current calendar date-based spring wheat planting systems used in the region. However, ultra-early planting when soils are cold (2 °C), and resulting early crop emergence, precludes most foliar pre-seeding weed control options. Field trials were conducted at three sites in western Canada from 2017 to 2019 to evaluate the crop safety, broadleaf weed efficacy, and growing system stability resulting from the inclusion of fall applications of soil-applied residual herbicides prior to planting wheat ultra-early the following spring. Flumioxazin (protoporphyrinogen oxidase inhibitor; Weed Science Society of America (WSSA) group 14) and pyroxasulfone (very long chain fatty acid synthesis inhibitor; WSSA group 15) were applied alone and in combination at multiple rates in the late fall prior to ground freeze. The following spring, hexaploid spring wheat was planted ultra-early, based on a soil temperature trigger of 2 °C, and later, triggered by a soil temperature of 8 °C. When planting was completed ultra-early, grain yield was greater, and variability of grain yield was lower. Herbicide treatments increased broadleaf weed control, and in some environments further increased grain yield and reduced grain yield variability without resulting in phytotoxicity. The ability to safely incorporate fall-applied residual herbicides into ultra-early spring wheat planting systems provides an option for growers to adopt ultra-early planting without negatively impacting weed management on their farms.

Learning to balance wheat G × E × M interactions in response to a changing climate—The case for ultra‐early planting systems

“…Slafer et al (2023) reported that grain yield was a function of the length of the wheat critical growth period and the growing conditions during that period. In ultra-early planting systems, the critical developmental period of wheat shifts to earlier in the growing season, occurs under cooler temperatures, and potentially lasts longer than when planting occurs later in the season (Collier et al, 2020(Collier et al, , 2021Collier, Spaner, Hall, et al, 2022). By shifting these sensitive growth stages earlier in the growing season, ultra-early planting has the potential to increase grain yield by optimizing wheat phenology within predominant environmental conditions on the northern Great Plains.…”

“…Ultra-early planting when soils are cold (≤2˚C), and resulting early crop emergence, precludes most foliar pre-seeding weed control options. Collier, Spaner, Hall, et al (2022) conducted field experiments at three sites in western Canada from 2017 to 2019 to evaluate the crop safety, broadleaf weed efficacy, and growing system stability resulting from the inclusion of fall applications of soil-applied residual herbicides prior to planting wheat ultra-early the following spring. Flumioxazin (protoporphyrinogen oxidase inhibitor; Weed Science Society of America [WSSA] group 14) and pyroxasulfone (very-long-chain fatty acid synthesis inhibitor; WSSA group 15) were applied alone and in combination at multiple rates in the late fall prior to ground freeze.…”

“…Producers should consider augmenting the improved weed competitive ability of ultra‐early‐planted wheat‐growing systems with the use of fall‐applied residual herbicides in fields intended to be planted ultra‐early. This growing system will lead to increased grain yield and increased growing system stability relative to current conventional wheat‐growing practices and increase the resiliency of wheat‐growing systems on the northern Great Plains (Collier, Spaner, Hall, et al., 2022). Further tactical development and intensification of the proposed ultra‐early spring wheat‐growing system for western Canada are in progress.…”

An improved design for a zero-tillage experimental plot drill

“…The drill was first used in conjunction with a newly conceptualized seeding system for wheat--"ultra-early wheat", and was first detailed in interim and final reports for that project (Beres et al 2018). It was further described in the subsequent studies and publications of ultra-early wheat seeding systems (Collier et al 2020b(Collier et al , 2021(Collier et al , 2022a(Collier et al , 2022b.…”