QUACKGRASS SUPPRESSION THROUGH CROP-ROTATION IN CONSERVATION TILLAGE SYSTEMS

Quackgrass [Elytrigia repens (L.) Nevski] is a widespread perennial we ed traditionally controlled by tillage, a practice which can contribut e to soil erosion and degradation. This study was initiated to determi ne the impact of integrated weed management strategies utilizing crop rotation, conservation tillage, and postemergence herbicides on quackg rass. Rotations of tall and semi-dwarf winter wheat (Triticum aestivum L. 'Norstar' and 'Norwin') or spring wheat (Triticum aestivum L. 'Kat epwa' and 'HY320') with mustard (Brassica juncea 'Common Brown') and f lax (Linum usitatissimum L. 'Norlin') were conducted at Indian Head, S askatchewan for 4 yr to determine their effect on quackgrass shoot den sity, rhizome dry weight and rhizome node density. The presence or abs ence 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 s pring 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. Sh oot density, rhizome biomass, and rhizome node density were not consis tently correlated to crop yield. Crop rotation is a useful component o f an integrated quackgrass management system.