|Spandl, Eric - UNIVERSITY OF MINNESOTA|
|Durgan, Beverly - UNIVERSITY OF MINNESOTA|
Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 1998
Publication Date: N/A
Interpretive Summary: Two grasses, green and yellow foxtail (pigeon grass), are the most troublesome weeds of small grain fields in the central and northern Great Plains. The timing of seedling emergence of these weeds is important for developing useful control practices. Two management practices that producers can easily change to affect weed emergence patterns are tillage system and planting dates. Consequently, foxtail seedbanks and emergence patterns were determined during three years (1994-96), for three planting dates (early, middle, late), and across three tillage systems (moldboard plow, chisel plow, and no-till) in continuous spring wheat in Fargo clay soil of the Red River Valley of Minnesota and North Dakota. Foxtails emerged faster but at lower densities in moldboard plow than other tillage systems. Foxtails emerged relatively slowly but in great numbers when wheat was sown in early May. In contrast, foxtails emerged quickly and at low densities when wheat was sown in late May. Practical application of this information, (1) delayed planting offsets the negative effects of reduced tillage in terms of foxtail densities, and (2) more rapid and uniform seedling emergence with delayed sowing increases single pass control of foxtail, but simultaneously decreases the window of opportunity for effective postemergence control of these weeds, will be of benefit to producers in selecting appropriate management and control practices.
Technical Abstract: Foxtail emergence patterns were evaluated in spring wheat under three tillage and planting regimes: moldboard plow, chisel plow, no-till and three wheat planting dates. The first planting date was as soon as feasible in spring while the second and third planting dates were 9 and 16 days later. Foxtail emergence patterns and seed bank density were evaluated each year in plots that were maintained with the same treatments for three consecutive years. Green foxtail was the dominant weed species. A tillage regime did not influence percent emergence of foxtail initially or as emergence approached 100%. However, foxtail emergence was lower in chisel plow and no-till than in moldboard plow regimes during intermediate emergence stages. By the third year, total foxtail plant emergence was greater in no-till and chisel plow than in moldboard plow and also greater in no-till than chisel plow. Earlier planting generally increased percent foxtail emergence until mid-season. At 22 days after planting, average emergence of foxtail was 48, 67, and 81% for planting dates one, two and three, respectively. Delayed planting increased rates of foxtail emergence but decreased density of emerged seedlings. Producers adopting chisel plow or no-till systems can expect to see greater foxtail infestations than in moldboard plow systems. Delaying wheat planting may be a viable option for foxtail management through reduced densities and more simultaneous emergence patterns.