|Anderson, Randal - Randy|
Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2006
Publication Date: 3/22/2007
Citation: Anderson, R.L., Stymiest, C., Swan, B., Rickertson, J. 2007. Weed community response to crop rotations in western South Dakota. Weed Technol. 21:131-135. Interpretive Summary: Cropping systems are changing in western South Dakota because of conservation tillage. Producers are adding a diversity of crops to the conventional rotation of winter wheat-fallow. The diversity of crops with different life cycles can disrupt weed population growth because of different planting and harvesting dates. This study showed that arranging rotations to include two cool-season crops such as winter wheat and peas followed by two warm-season crops such as corn and sunflower will be least favorable for weed community growth. Producers can reduce input costs for weed management 50% with rotations designed in this fashion, when included with other cultural tactics. Cropping systems are being developed in this region that are not so dependent on herbicides for efficient weed management.
Technical Abstract: Producers in the semiarid Great Plains are exploring alternative crop rotations, with the goal of replacing winter wheat-fallow. In 1993, a study was established to compare performance of eight rotations comprised of various combinations with winter wheat (W), spring wheat (SW), dry pea (Pea), safflower (Saf), corn (C), sunflower (Sun), proso millet (M), or fallow (F). Weeds were managed with a combination of herbicides and subsurface tillage. After eight years, we characterized weed communities by recording seedling emergence in each rotation. Seventeen species were observed, with downy brome, kochia, horseweed, and stinkgrass comprising 87% of the community. Rotations with the least number of weed seedlings were W-F and SW-W-C-Sun; in comparison, weed density was six-fold higher in W-M. Density of downy brome and kochia was related to canopy development and frequency of winter wheat in rotation. Stinkgrass and green foxtail were prominent in proso millet, but their density was related to frequency of warm-season crops in rotation. Horseweed established readily in safflower and dry pea. In the semiarid Great Plains, designing rotations in a cycle-of-four that include cool- and warm–season crops can be a key component of integrated weed management. Index words: crop diversity, crop rotation