The Effect of Oxygen Concentration on the Germination of Some Weed Species under Control Conditions

Continuous use of heavy machinery in fields and frequent farm traffic sometimes result in soil compaction. Soil compaction reduces the oxygen (O₂) concentration in soil capillaries and hence lowers the O₂ availability for germinating seeds. We investigated how reduced O₂ levels changed germination behavior of weeds to elucidate their potential to adapt to O₂-deficient soils (compacted, compressed, and waterlogged soils and soils with hard surfaces). Two similar laboratory experiments were conducted with five O₂ treatments (20.9%, 15%, 10%, 5%, and 2.5%). The germination percentage of the invasive weed hairy fiddleneck [Amsinckia menziesii (Lehm.) A. Nelson & J.F. Macbr. var. menziesii] and the common weeds common lambsquarters (Chenopodium album L.) and Persian speedwell (Veronica persica Poir) was not significantly reduced at 15% O₂. The germination of scarlet pimpernel (Anagallis arvensis L. ssp. arvensis), silky windgrass [Apera spica-venti (L.) Beauv.], catchweed bedstraw (Galium aparine L.), and knawel (Scleranthus annuus L.) was significantly reduced at 15% O₂. The highest germination was obtained at 20.9% O₂ for blackgrass (Alopecurus myosuroides Huds.), A. spica-venti, G. aparine, annual bluegrass (Poa annua L.), wild mustard (Sinapis arvensis L.), scentless chamomile [Tripleurospermum inodorum (L.) Sch. Bip.], field violet (Viola arvensis Murray) and the less common weeds A. arvensis and S. annuus. Distribution of flora in the landscape may change on O₂-deficient soils by reducing germination of some species such as A. arvensis and S. annuus and favoring others like A. menziesii and C. album. The ability to germinate at 2.5% and 5% O₂ may contribute to explain why A. myosuroides and A. menziesii have become successful as weeds on O₂-deficient soils, as they maintained a germination percentage between 34% and 58% at 2.5% O₂.