Monday, November 5, 2007
71-2
Growth Analysis of Faba Bean and Lupin Under Grassy Weed Competition in a Northern Environment.
Grassy weed pressure can significantly decrease the productivity of faba bean (Vicia faba L.) and narrow leafed lupin (Lupinus angustifolius L.). Field experiments were conducted in north central Alberta, Canada between 2004 and 2006. Faba bean and lupin were grown with barley (Hordeum vulgare L.), as a model weed, at 3 densities (0, 25, and 50 plants m2). Leaf area (LA) development, photosynthetically active radiation (PAR) interception, and dry matter (DM) accumulation of faba bean and lupin were measured at 21-d intervals between 35 and 143 d after planting (DAP). Leaf area peaked 79 to 98 DAP, depending on the year, with marked differences between species. Faba bean and lupin, grown without grassy weeds, increased LA at a mean rate of 0.055 and 0.036 m2 d-1, respectively, between 35 and 98 DAP. A low grassy weed density reduced the mean rate of LA development to 0.032 and 0.013 m2 d-1 for faba bean and lupin, respectively. At early growth stages (55-59 DAP), weed free lupin intercepted less (mean 64%) incident PAR than faba bean (mean 80%). In general, weed presence did not affect the amount of incident light available at the top of the faba canopy. However, due to the height advantage of grassy weeds over lupin, the amount of light available at the top of the lupin canopy was reduced by 51%, 98-100 DAP. At physiological maturity, mean faba bean DM accumulation was 1161, 635, and 417 g m-2 for grassy weed densities of 0, 25, and 50 plants m2, respectively. Mean lupin DM accumulation, at physiological maturity was 1088, 304, and 200 g m-2 for grassy weed densities of 0, 25, and 50 plants m2, respectively. The poor competitive ability of lupin, relative to faba bean, may be attributed to slow early season LA development, short stature, and poor radiation interception.
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