Flixweed (Descurainia sophia) Shade Tolerance and Possibilities for Flixweed Management Using Rapeseed Seeding Rate

Abstract

Brassicaceae weeds can be problematic in canola varieties that have not been modified to resist specific broad-spectrum herbicides. The overall objective of this study was to evaluate the potential for increased rapeseed seeding rate as a management strategy for flixweed. To accomplish this objective, a field study was conducted to determine crop seeding rate effects on canopy light transmission and rapeseed yield characteristics, as well as a greenhouse study to determine morphological and photosynthetic responses of flixweed to decreasing irradiance levels. Results from the field study indicated that light transmittance through the canopy decreased linearly as crop seeding rate increased from 1.8 to 9.0 kg ha-1. Increasing crop seeding rate did not influence rapeseed aboveground biomass, seed yield, and harvest index, but negatively affected rapeseed seed oil content in one of two site-years. Greenhouse study results indicated that declining irradiance levels caused reductions in flixweed biomass, root allocation, and photosynthetic light compensation point. Flixweed leaf allocation, foliage area ratio, and specific foliage area increased in response to decreasing irradiance levels. Combined results of field and greenhouse studies suggest that increasing rapeseed seeding rate can suppress flixweed growth while not causing yield penalties from increased intraspecific competition. However, increased rapeseed seeding rate might not be an adequate control strategy on its own because flixweed displays characteristics of a shade-tolerant species.

Effect of Shading on Interspecific Competition Between Aegilops tauschii and Triticum aestivum

“…Shen et al (2021) showed that according to the changes in the growth and competitiveness of the invasive plant A. adenophora during shading treatment, the crop Helianthus tuberosus L. could be used as an alternative control in the invaded shadowy orchard and forest edges. Landau et al (2017) showed that as rapeseed seeding rate increases, its canopy light transmittance decreases linearly, and the weakening of light suppresses the growth of the weed species Descurainia sophia to some extent. erefore, increasing the seeding density of rapeseed may be considered an effective strategy to inhibit D. sophia.…”

“…is proportional to a moderate increase in the sowing rate (Butts et al, 2016). However, the effective control of weeds by an increase in the crop planting rate depends to a certain extent on the shade tolerance of the target weeds (Landau et al, 2017). Hence, knowledge of shade effects on the growth and competition of targeted weeds will provide insight into the potential effectiveness of this strategy.…”