Agronomy Library > Soil Conservation

Tillage Intensity and Crop Rotation Effects (Weed Dynamics in Winter Wheat)
Author: R. E. Blackshaw et al.
Date Created: February 20, 2002
Last Reviewed: February 28, 2007

Document Source: Canadian Journal of Plant Science 81: 805-813

Development of improved weed management system requires knowledge on how various weed species respond to changing agronomic practices. A long-term study was conducted to determine the weed population responses to various tillage intensities and crop rotations in winter wheat dominated cropping systems.

- Weed density and species composition differed with tillage, rotation, year and date of sampling within years.

- Weed community dynamics were most affected by year-to-year differences in environmental conditions, followed by crop rotation and then tillage intensity. 

- Russian thistle (Salsola iberica) and kochia (Kochia scoparia) densities increased in years of low rainfall and above average temperatures. Winter annual weeds such as downy brome (Bromus tectorum) and flixweed (Descuraina sophia) as well as perennial dandelion (Taraxacum officinale) increased in years where higher than average rainfall was received in fall or early spring.

- Continuous winter wheat facilitated a dense downy brome infestation to develop over time. Trifluralin is not efficacious on stinkweed or Canada thistle and its use in canola resulted in an increase in these species in a winter wheat-canola rotation.

- Total weed densities were often greater in zero tillage than in either minimum or conventional tillage. Russian thistle, downy brome, kochia, and redroot pigweed were associated with zero tillage, while wild buckwheat, flixweed and wild mustard were associated with conventional tillage. Perennials such as dandelion and sow thistle were associated with zero tillage but Canada thistle was associated with conventional tillage.