Differences in periodicity and depth of weed seedling recruitment due to agronomic management practices, such as reduced tillage, have implications for weed competitive ability and management strategies. Periodicity and depth of seedling recruitment of 10 different weed species was measured in the field in 2004 and 2005. The seedling recruitment of rigid ryegrass, threehorn bedstraw, and wild radish seedlings was higher under minimum tillage than under no-till scenarios. In contrast, the seedling recruitment of Oriental mustard, annual sowthistle, squirreltail fescue, little mallow, and turnipweed was higher under the no-till system. The seedling recruitment of wild oat and African mustard was not influenced by the tillage system. The mean seedling recruitment depth of wild oat, rigid ryegrass, threehorn bedstraw, wild radish, and turnipweed was greater under minimum tillage than under the no-till system. These weeds are able to emerge from deeper in the soil profile. In contrast, the seedling recruitment depth under minimum-tillage and no-till systems was similar for African mustard, Oriental mustard, annual sowthistle, little mallow, and squirreltail fescue. These are all small-seeded species, which failed to emerge from deeper depths under either tillage system. In addition, all of these species except African mustard showed higher total seedling recruitment under the no-till system. Results of this study will facilitate weed-control timing decisions and provide validation data for weed seedling recruitment models.

Nomenclature: Wild oat, Avena fatua L., AVEFA; African mustard, Brassica tournefortii Gouan, BRSTO; threehorn bedstraw, Galium tricornutum Dandy, GALTC; rigid ryegrass, Lolium rigidum Gaudin, LOLRI; little mallow, Malva parviflora L., MALPA; wild radish, Raphanus raphanistrum L., RAPRA; turnipweed, Rapistrum rugosum (L.) All., RASRU; Oriental mustard, Sisymbrium orientale L., SSYOR; annual sowthistle, Sonchus oleraceus L., SONOL; squirreltail fescue, Vulpia bromoides (L.) S.F. Gray, VLPBR.