Weed interference period and economic threshold level in barley

Determination of interference periods, competitive ability and economic threshold level ( ETL ) are important tools for integrated weed management (IWM) in barley. The objec-tive of the work was to determine the periods of interference, the competitive ability and the ETL of weeds in barley ( Hordeum vulgare ). Two field experiments were carried out, in a randomized block design, with four replications. In this study, the periods of coexistence and control for ryegrass ( Lolium multiflorum ) and turnip ( Raphanus raphanistrum ) infesting barley cultivar, cv. ANA 01 were evaluated. The coexistence periods and/or control were: 0, 7, 14, 21, 28, 35, 42 and 120 days after barley emergence (DAE). In experiment 2the treatments for determination of ETL s were composed by barley cultivars (BRS Suábia, ANA 01, BRS Korbel, BRS Manduri, BRS Cauê and BRS Greta), and turnip densities, from zero (0) to maximum densities of 816, 788, 948, 394, 584 and 618 plants · m − 2 , in competition with each cultivar. Control of turnip and ryegrass should be adopted in barley in the period between 12 to 22 DAE, which is described as a critical control period. The rectangular hyperbola adequately estimates losses in grain yield due to turnip infestation. There is an effect on the competitive ability of the cultivars in relation to turnip, which resulted in ETL s that ranged from 0.27 to 1.99 plants · m − 2 . The cultivars BRS Greta, BRS Suábia, ANA 01 and BRS Manduri were the most competitive in the presence of turnip.