Weed seedling emergence is partially dependent on biotic and abiotic conditions directly surrounding the seed. When environmental conditions are appropriate, seed germination and emergence occurs. We studied the impact of seeding depth (surface, 1 to 2, 3 to 4, and 6 to 7 cm) and fluctuating soil moisture regimes (field capacity [FC]–1/3FC–FC; FC–1/6FC–FC) on percent weed emergence in a greenhouse. At FC, wild mustard and field pennycress had the greatest percent emergence when seeds were placed on or near the soil surface, whereas percent emergence of barnyardgrass and round-leaved mallow was unaffected by seeding depth. All the perennials tested had the greatest percent emergence at FC when seeds were placed near or on the soil surface, except for common milkweed which only emerged below the soil surface. When soil moisture levels fluctuated, surface seeds of barnyardgrass, catchweed bedstraw, green foxtail, wheat, and wild oat had less emergence than seeds below the soil surface; field pennycress had increased emergence when the seeds were placed on the surface; and round-leaved mallow and wild mustard emergence was unaffected by seeding depth. The emergence of curly dock, dandelion, and perennial sowthistle was unaffected by seeding depth, whereas foxtail barley and quackgrass emergence was reduced when seeds were placed on the surface and soil moisture fluctuated.
Nomenclature: Barnyardgrass, Echinochloa crus-galli L. ECHCG; catchweed bedstraw, Galium aparine L. GALAP; common milkweed, Asclepias syriaca L. ASCSY; curly dock, Rumex crispus L. RUMCR; dandelion, Taraxacum officinale Weber in Wiggers TAROF; field pennycress, Thlaspi arvense L. THLAR; foxtail barley, Hordeum jubatum L. HORJU; green foxtail, Setaria viridis (L.) Beauv. SETVI; perennial sowthistle, Sonchus arvensis L. SONAR; quackgrass, Elytrigia repens (L.) Nevski AGGRE; round-leaved mallow, Malva pusilla Sm. MALSU; spring wheat, Triticum aestivum L. ‘AC Barrie’ wild mustard, Brassica kaber (D.C.) L.C. Wheeler SINAR; wild oat, Avena fatua L. AVEFA.