Burial Environment Drives Seed Mortality of Kochia (Bassia scoparia), Wild Oat (Avena fatua), and Volunteer Canola (Brassica napus) Irrespective of Crop Species.

Charles M Geddes

doi:10.3390/plants10091961

Abstract

Models of weed population demography are critical to understanding the long-term viability of management strategies. The driving factors of weed seedbank persistence are often underrepresented in demographic models due to the cumbersome nature of seedbank research. Simplification of weed seedbank dynamics may induce substantial error in model simulations. A soil bioassay was conducted to determine whether growth of different crop species, including wheat (Triticum aestivum L.), canola (Brassica napus L.), and field pea (Pisum sativum L.), differentially impact seed mortality of kochia [Bassia scoparia (L.) A.J. Scott], wild oat (Avena fatua L.), and volunteer canola in seven burial environments in western Canada. Weed seed survival after the 7 week burial period varied widely among burial environments (from 8% to 88% when averaged among weed and crop species), whereas growth of the different crop species had negligible impact on seedbank persistence. Among environments, wild oat seed survived the greatest (79%), followed by kochia (20%), and volunteer canola (6%). Weed seed survival was associated with soil physical properties (texture) and seed microsite characteristics (temperature), but not crop species or soil chemical properties. Overall, these data support the need for greater integration of soil and environmental parameters into models of weed population demography.

Highlights

There was a general trend among environments where a greater percentage of wild oat seeds survived compared with kochia and volunteer canola, with the exception of burial environment 5 in which similar seed mortality was observed for all three weed species (Figure 2)
Giant foxtail (Setaria faberi Herrm.), common lambsquarters (Chenopodium album L.), and velvetleaf (Abutilon theophrasti Medik.) seedbank persistence ranged among environments from 7–42%, 5–95%, and 5–88%, respectively, after one year of burial in a multi-site-year study across the U.S
In a common garden study of nine soils in western Canada, volunteer canola seed survival after 5 months of burial over winter was greater among the clay soils compared with the sandy loam and loamy sand soils, whereas the opposite relationship was observed over summer [13]

Summary

Introduction

Recent 2014–2017 estimates for the Canadian prairie region (comprising 87% of annual-cropped area in Canada) suggest that herbicide-resistant weeds infest about 9.6 M ha (35% of total area) of farmland under annual crop production, which has grown from 7.7 M ha (29%) in 2007–2009, and. The most recent round of surveys estimated that herbicideresistant weeds cost prairie farmers CAD 530 M annually in increased herbicide usage, and decreased crop yield and quality [1]. Kochia [Bassia scoparia (L.) A.J. Scott], wild oat (Avena fatua L.) and volunteer canola (Brassica napus L.) are among the most problematic weed species impacting prairie cropland in Canada. In a 2017 survey of 1232 annual-cropped fields in Alberta, CA, kochia, wild oat, and volunteer canola were the 15th, 5th, and 4th most abundant weeds present after post-emergence herbicide application [2]. Wild oat and volunteer canola were abundant throughout the agricultural production area of Alberta [2]

Methods

Results

Conclusion