ARS | Publication request: Weed Community Emergence Pattern in Eastern South Dakota

Submitted to: Western Society of Weed Science Research Reports
Publication Type: Research Notes
Publication Acceptance Date: January 8, 2009
Publication Date: March 9, 2009
Citation: Anderson, R.L. 2009. Weed Community Emergence Pattern in Eastern South Dakota. Western Society of Weed Science Research Reports, pp. 155-156.

Interpretive Summary: Our research program is seeking to develop a population-centered approach to weed management. A key component of this approach is understanding weed seedling emergence. In this study, we characterized the emergence of weed seedlings commonly found in this region across a three-year interval. Most weeds emerged during May and June. Seedlings emerged earlier when the sites had been tilled the previous fall. We also quantified emergence density across years, and found that emergence in the third year was only 10% of emergence in the first year. Producers can gain an advantage for managing weeds if they choose to grow crops with different growth periods than corn and soybean. This practice will help producers accrue the advantage of rapid loss of weed seed viability across time. The population-centered approach has reduced need for herbicides 50% in the drier regions of the Great Plains.

Technical Abstract: Producers who followed rotations comprised of crops with different growth periods are able to manage weeds with less herbicides. The diversity in growth periods provides more opportunities for producers to prevent weed seed production. In our research program, we are exploring impact of cool-season crops on weed dynamics in the corn-soybean rotation. Our first goal was to quantify the emergence pattern of weeds common in the corn-soybean rotation. Weed seedling emergence in six permanent quadrats (0.5 m2 in size) were monitored across a three-year interval. Quadrats were established in both no-till and tilled systems. More than 80% of seedlings emerged in May and June. Seedlings emerged both earlier and at a greater density with tillage. Comparing seedling density between years, the number of seedlings in no-till in the third year was 65, contrasting with 626 seedlings emerging in the tilled quadrats in the first year. The two-year interval with no-till reduced weed density almost 90%; producers can accrue the benefit of this natural decline in seedling emergence by adding crops such as winter wheat to the corn-soybean rotation.