|Anderson, Randal - Randy|
Submitted to: Weed Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/27/2006
Publication Date: 3/22/2007
Citation: Anderson, R.L., Beck, D.L. 2007. Characterizing weed communities among various rotations in central South Dakota. Weed Technol. 21:76-79. Interpretive Summary: With the development of no-till systems, producers are changing their crop rotations in central South Dakota. Along with winter wheat, producers now grow a diversity of crops. Crop diversity can disrupt weed population growth, especially if crops in sequence have different planting and harvesting dates. This study showed that rotation design can have a major impact on weed community density. Arranging rotations to include two cool-season crops such as winter wheat and dry pea followed by two warm-season crops such as corn and soybean was the least favorable for weed community growth. Weed community density differed 13-fold between rotations. Furthermore, this rotation design also improves crop growth and yield due to the rotation effect.
Technical Abstract: Producers in the Great Plains are exploring alternative crop rotations, with the goal of reducing the use of fallow. In 1990, a study was established with no-till practices to compare performance of eight rotations comprised of various combinations of winter wheat (W), spring wheat (SW), corn (C), chickpea (CP), dry pea (Pea), soybean (SB), or fallow (F). After 12 years, we characterized weed communities by recording seedling emergence in each rotation. Downy brome, cheat, redroot pigweed, and green foxtail were the most common weeds observed. Weed community density was highest for W-CP, being 13-fold greater than weed density with Pea-W-C-SB. Density of downy brome and cheat were related to how frequently winter wheat appeared in the rotation. Warm-season weeds such as redroot pigweed and green foxtail were least prominent if a two-year interval of cool-season crops were included in the rotation. Based on results from three long-term rotation studies in the semiarid Great Plains, we suggest that arranging crops in a cycle of four, with two cool-season crops followed by two warm-season crops, will reduce weed community density compared to rotations with less crop diversity. Index words: crop design, no-till