Cropping systems to control winter annual grasses in winter wheat (Triticum aestivum)

Field studies were conducted from 1990 through 1997 to evaluate the long-te rm effect of 2- and 3-yr rotations on the control of downy brome, jointed g oatgrass, and feral rye in winter wheat. At the completion of the study, jo inted goatgrass and feral rye densities averaged 8 plants/m(2) and <0.1 pla nt/m(2) for the 2- and 3-yr rotations, respectively. Downy brome densities averaged <0.5 plant/m(2) for both the 2- and 3-yr rotations, with no treatm ent differences observed. Winter annual grasses were not eradicated after t wo cycles of the 3-yr rotations, but weed densities were reduced 10-fold co mpared to densities after one cycle and more than 100-fold compared with th e 2-yr rotations. Wheat grain contamination with dockage and foreign materi al followed a similar trend. The 3-yr rotations were economically competiti ve with 2-yr rotations and provided superior control of the winter annual g rass weeds.