The Journal of Agricultural Science

Crops and Soils

The influence of winter oilseed rape (Brassica napus ssp. oleifera var. biennis) cultivar and grass genotype on the competitive balance between crop and grass weeds

L. C. SIMa1 c1, R. J. FROUD-WILLIAMSa1 and M. J. GOODINGa2

a1 School of Biological Sciences (TOB2), University of Reading, Earley Gate, Reading RG6 6AU, UK

a2 School of Agriculture, Policy, and Development, University of Reading, Earley Gate, Reading RG6 6AU, UK

SUMMARY

Three experiments conducted over two years (2002–04) at the Crops Research Unit, University of Reading, investigated competition between autumn sown oilseed rape cultivars (Brassica napus L. ssp. oleifera var. biennis (DC.) Metzg.) and Lolium multiflorum Lam., Lboucheanum Kunth and Alopecurus myosuroides Huds., sown as indicative grass weeds.

Rape cultivar (cv.) had a substantial effect on grass weed seed return. Over the six cultivars tested, L. multiflorum spikelet production ranged from just under 400 spikelets/m2 in the presence of cv. Winner to nearly 5800 in competition with cv. Lutin. Cultivar competitiveness was associated with high biomass, large dense floral layers and early stem extension. There was some evidence of differential competitive tolerance between rape cultivars.

The results suggested that rape cultivars could be screened for competitiveness by measuring floral layer interception of photosynthetic active radiation.

Lboucheanum cultivars varied in ability to compete with rape. In the absence of inter-specific competition, spikelet density was similar for Aberecho and Polly (circa 31 000 spikelets/m2) but when grown with rape Polly outyielded Aberecho (i.e. 12 090 and 7990 spikelets/m2 respectively).

(Received November 20 2006)

(Online publication January 16 2007)

Correspondence:

c1 *To whom all correspondence should be addressed. Present address: Archway House, Fairfield Road, Goring, Reading, RG8 0EX, UK. Email: sim.agronomy@virgin.net

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