Sustainable Agriculture Program, Department of Plant, Soil and Environmental Sciences, University of Maine, Orono, ME 04469 5722, USA.
*E-mail: gallandt@maine.edu
Weed Science 53: 695–701, (2005).
Field experiments were conducted in Maine, USA, during the 2002 and 2003 cropping seasons, to determine whether incorporated Brassica cover crops, including rape, rapeseed and yellow mustard, reduce subsequent weed and crop establishment. Related field experiments that examined the influence of Brassica cover crops on plant growth was also conducted. Emergence rate and total emergence of 16 weed and crop bioassay species were measured following Brassica cover crops, fallow or incorporated residues of other short-season cover crops including oat, crimson clover and buckwheat. The bioassay species, representing a range of seed sizes, were chosen to determine whether larger seed size confers protection from residue-mediated effects on emergence. Averaged over bioassay species, Brassica cover crops reduced emergence by 23 to 34% compared to fallow; emergence following brassicas was delayed by approximately 2 days. The effects of the incorporated Brassica residues were similar to those of the other short-season cover crops, which reduced emergence of the bioassay species by 19 to 39% and delayed emergence by 2 days. Seed size was a poor predictor of a species' establishment. Brassica residues are capable of delaying seedling emergence and reducing establishment, although the magnitude of their effects were comparable to other widely available cover crops.
