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Title: WEED SEEDBANK DYNAMICS IN ORGANIC AND CONVENTIONAL LONG-TERM CROPPING SYSTEMS

Author
item Ullrich, Silke
item Teasdale, John
item Cavigelli, Michel

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/4/2003
Publication Date: 12/1/2003
Citation: Ullrich, S.D., Teasdale, J.R., Cavigelli, M.A. 2003. Weed seedbank dynamics in organic and conventional long-term cropping systems [abstract]. Amer. Soc. Agronomy Abstracts [CDROM]. A08-ullrich412133-Oral.

Interpretive Summary: none needed

Technical Abstract: Weed management is one of the biggest challenges in organic farming. The Farming Systems Project (FSP) in Beltsville, MD, compares five cropping systems, two conventional and three organic. Overall, there has been no long-term increase in the weed seed bank over the first six years. However, there were oscillations in all major species depending on weather, crop, and weed management success. The annual variation in the size of the weed seed bank could be explained by the initial seed bank in the beginning of the season and the weed seed input during the season. Strong declines in the seed bank following years with a large seed bank indicate a high mortality of the seeds in the soil. Weed seed survival in the soil was studied in more detail using buried nylon mesh bags or unenclosed soil cores in FSP and at the Farming Systems Trial (FST) at the Rodale Institute. Comparing the three organic systems in FSP, the seed bank and weed abundance of the dominant species tended to be highest in the two year rotation, intermediate in the three-year rotation and lowest in the four year rotation. This confirms that the more varied and longer the rotation, the lower the population of annual weeds. Organic cropping systems should be designed to offer a variety of mechanisms acting on various stages of the life cycle of annual weeds to regulate weed populations.