Agronomy Library > Annual Weeds

Crop Rotations and Tillage Effects on Weed Populations
Author: R. E. Blackshaw, F. O. Larney, W. Lindwell, and G. C. Kozub
Date Created: February 10, 1994
Last Reviewed: January 22, 2009
Document Source: Weed Technology, Volume 8: 231-237  Summary A long-term study was conducted at Lethbridge Alberta to determine the response of weed populations to various crop rotations and tillage treatments: - Weed density and species composition differed with rotations, tillage and date of sampling within years. - Fewer weeds were found in winter wheat-fallow than in continuous winter wheat, winter wheat - lentil or winter wheat canola rotations. - A dense infestation of downy brome developed in continuous winter wheat rotation. - In all rotations more weeds were present in zero tillage plots than in either minimum or conventional tillage plots. - Dandelions and perennial sow thistle densities increased slightly over years in minimum and zero tillage treatments. Flixweed, field pennycress, wild buckwheat, and common lamb's quarters densities decreased in zero tillage but densities of downy brome, redroot pigweed and Russian thistle increased. Russian thistle was not well controlled with trifluralin and its density increased in winter wheat-canola rotations. Message: Changes in crop sequence and seeding practice (tillage intensity, soil disturbance, seeding date, fertilizer placement, etc.) can affect weed populations.