Aboveground weed competitive ability of spring wheat (Triticum aestivum L.) in organic and conventional management systems.

摘要

The use of competitive spring wheat (Triticum aestivum L.) cultivars may reduce the negative effects of weed competition in organic and conventional systems. A series of studies were conducted to evaluate the agronomic performance and competitive ability of spring wheat cultivars under organic and conventional farming systems, and to identify traits conferring competitive ability in organically grown wheat. Twenty-seven Canada Western Red Spring wheat cultivars, representing 114 years of Canadian wheat breeding, were grown under organic and conventional management in field trials conducted from 2002-2004. Cultivars performed differently in the two management systems, suggesting that there may be some cultivars better suited to organic than conventional management systems. Of the 27 bread wheat cultivars, five were selected to be evaluated for their breadmaking quality when grown in the two management systems. Although differences were detected between the two systems, results suggest that growing high quality bread wheat under organic management systems in north central Alberta is possible. There was no evidence in either of these studies suggesting that older cultivars are better suited to organic production than modern cultivars. An additional set of 11 spring wheat and barley cultivars differing in height, tillering and maturity characters were grown at recommended (300 seeds m-2) and doubled seeding densities, with or without competition from tame oats, under organic management in 2003 and 2004. Cultivars differed in their abilities to achieve and maintain grain yield under competition, and to suppress weeds. Barley was generally more competitive than wheat. Doubling the seeding rate increased grain yield, weed suppression and economic returns, suggesting that it is a suitable strategy for overcoming weed competition in organic grain production. We investigated the stability and adaptation of 9 wheat cultivars in differing natural weed environments. Older cultivars were the most yield stable across a wide range of environments, while semidwarf cultivars were the least weed stable. Height, early season vigour, time to heading and maturity, and tillering were identified as traits related to cultivar competitive ability. A competitive crop ideotype for organic agriculture would be a tall plant with strong early season vigour, and early heading and maturity.