Weed seedbank community responses to crop rotation schemes

Improved weed management strategies may be possible through rotational schemes which alter the weed seedbank community. This study investigated the effects of 2-year crop rotations with alfalfa (Medicago sativa L.), clover (Trifolium pratense L.), rye (Secale cereale L.), or sweet corn (Zea mays L. var. rugosa Bonaf.) on weed seedbank density and diversity at three sites in New York. Weed seedbank density and diversity increased under all rotational schemes over the 2 years, but increases were generally lowest after sweet corn, in which tillage and herbicides were used. By the end of the second year, seed densities of individual weed species had changed to different extents in response to rotational crop. Most of the instances in which seed densities increased significantly were associated with rye. Although pre- and post-emergence herbicides plus tillage were used with sweet corn, weed seedbank densities were similar compared with the alfalfa and clover rotations, in which no herbicides nor tillage were used. Our results indicate that legumes could be a component in the sustainable management of weeds through manipulation of the seedbank. A rye cover crop did not appear to deter seed return nor recruitment to the seedbank as much as the legumes did. (C) 2003 Elsevier Ltd. All rights reserved.