QUACKGRASS SUPPRESSION THROUGH CROP-ROTATION IN CONSERVATION TILLAGE SYSTEMS

Quackgrass [Elytrigia repens (L.) Nevski] is a widespread perennial weed traditionally controlled by tillage, a practice which can contribute to soil erosion and degradation. This study was initiated to determine the impact of integrated weed management strategies utilizing crop rotation, conservation tillage, and postemergence herbicides on quackgrass. Rotations of tall and semi-dwarf winter wheat (Triticum aestivum L. 'Norstar' and 'Norwin') or spring wheat (Triticum aestivum L. 'Katepwa' and 'HY320') with mustard (Brassica juncea 'Common Brown') and flax (Linum usitatissimum L. 'Norlin') were conducted at Indian Head, Saskatchewan for 4 yr to determine their effect on quackgrass shoot density, rhizome dry weight and rhizome node density. The presence or absence of winter wheat within the crop rotation had the greatest impact on quackgrass growth. During years when drought hampered winter wheat establishment, quackgrass growth was greater in winter wheat than in spring wheat, but under conditions favoring winter wheat establishment, the opposite occurred. Quackgrass growth in standard height wheat was similar to semi-dwarf wheat. Annual differences in quackgrass growth occurred between mustard and flax, but overall, no trend developed. Shoot density, rhizome biomass, and rhizome node density were not consistently correlated to crop yield. Crop rotation is a useful component of an integrated quackgrass management system.