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The hypothesis of this study is that the weed population dynamics differ between organic and conventional cropping systems. It is believed that weeds are more common under diverse organic cropping systems but less problematic.

The overall objective of this experiment is to determine how weed population dynamics differ between organic and conventional cropping systems and rotations.

To do this the following sub-objectives will be addressed:

1. Determine how cropping system and rotation affect weed populations (plant density, seed bank density) over time
2. Determine how weed populations affect weed biomass, crop yield and crop yield loss
3. Determine how drivers of weed population dynamics including seed bank survival, seedling emergence and biomass accumulation differ between cropping system and rotation.

Weeds are perceived to be a large problem in organic crop production. The effect of organic crop rotations on crop yield loss due to weeds and on the population dynamics of weeds is not known. The overall objective of this experiment is to determine the effect of organic crop rotations on weed populations. It is believed that diverse crop rotations will have greater seedbank losses, reduced weed seed emergence and reduced yield losses from weeds.

The first approach will be to conduct a historical statistical analysis of the weed related data from the Alternative Cropping Systems (ACS) trial located at Scott, SK. This trial will be in year 17 and 18 for the final two years of this research program. Statistical analysis will determine the effect of crop rotations and cropping system on weed and yield parameters over time. In this way we will determine crop rotations that reduce weed populations and maintain acceptable yields over time.

The second approach will consist of imposing small subplots into select treatments of the ACS. The intent of the subplot experiments is to determine how weed population dynamics differ between specific systems. We will measure granivory, yield loss, weed biomass accumulation and seedling emergence in the wheat phase of the no-tillage and organic crop rotations. The subplot experiments will inform us as to how organic crop rotations affect weed populations over time.

The overall result of this research will be the identification of organic crop rotations which reduced yield losses and weed populations. 

• Do organic weed control systems have a fit in controlling herbicide resistance?
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• • Weed Technology (2013) 27: 204-211
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