Periodicity of Germination and Emergence of Some Annual Weeds

Abstract

Seeds of yellow foxtail [Setaria lutescens(Weigel) Hubb.], ivyleaf morningglory [Ipomoea hederacea(L.) Jacq.], common cocklebur (Xanthium pensylvanicumWallr.), jimsonweed (Datura stramoniumL.), velvetleaf (Abutilon theophrastiMedic.), and giant ragweed (Ambrosia trifidaL.) were buried in the soil November 20 and 21, 1966 at Urbana, Illinois for noting emergence of seedlings from April 1 through August 18, 1967. Similarly, seeds of yellow foxtail, ivyleaf morningglory, jimsonweed, velvetleaf, giant ragweed, common ragweed (Ambrosia artemisiifoliaL.), and Pennsylvania smartweed (Polygonum pensylvanicumL.) were buried on October 25, 1968 for emergence observations from April 1 to August 18, 1969. Pennsylvania smartweed, giant ragweed, and common ragweed had large flushes of germination from early April through early May, with no emergence after June 1. Velvetleaf displayed similar early flushes and had additional small flushes of emergence in late May or June. Yellow foxtail seedlings also emerged in April and May in 1969 and in May and June during both years. Common cocklebur seedlings emerged abundantly in April and May but less abundantly in June. Ivyleaf morningglory and jimsonweed displayed flushes of emergence sporadically after May 1. Flushes of emergence for all species which occurred after May 1 were preceded by sufficient rainfall to bring the surface 10 cm of soil to field capacity. Cumulative heat units in the soil above 10 C were not correlated with initiation of emergence for any species. The early emergence was attributed to stimuli from general soil warming while emergence after May 1 was stimulated by favorable soil moisture from rainfall.

Dormancy and longevity of annual ryegrass (Lolium rigidum) as affected by soil type, depth, rainfall, and duration of burial

“…Inhibition of germination due to soil depth has been reported for many species e.g. by Holm (1972), Stoller and Wax (1973), Benvenuti andMacchia (1995, 1997) and Benvenuti et al (2001), including L. rigidum (Gramshaw and Stern 1977). Chauhan et al (2006b) reported that regardless of burial depth, the dormant L. rigidum seed component present at the end of a growing season was quite small (4-16%).…”

Effect of No-Till or Conventional Planting and Cover Crops Residues on Weed Emergence in Vegetable Row Crop

“…Spring soil tillage usually results in an increase in emergence of annual broadleaf weeds (Froud-Williams et al 1984;Shilling et al 1986). This increase in weed emergence is often synchronized with crop emergence and is attributed to the strong periodicity of germination in many summer annual weeds (Roberts and Bodrell 1983;Roberts and Lockett 1978;Stoller and Wax 1973) coupled with seed exposure to germination promoters. Spring tillage increases the proportion of seeds that germinate and emerge by exposing weed seeds to germination promoters such as light (Scopel et al 1994), increasing the probable zone of emergence for small-seeded weeds (Mohler and Galford 1997), and reducing the mechanical resistance of the soil to emerging weed seedlings (Morton and Buchele 1960).…”

Interactions between substrate temperature and humidity in signalling cyclical dormancy in seeds of two perennial tropical species

“…Seeds submitted to humid/dry treatments demonstrated a gradual alleviation of dormancy after suspending irrigation (dry substrate) but subsequent increases in dormancy levels once the soil became humid again. A number of workers have shown that seed desiccation followed by rehydration can induce Signalling cyclical dormancy in seeds of tropical species secondary dormancy (Staniforth and Cavers, 1979;Downs and Cavers, 2000), and that periodic changes in soil humidity can affect the dormancy levels of buried seeds (Batlla and Benech-Arnold, 2010) -thus acting as an additional signalling factor for secondary dormancy (Stoller and Wax, 1993;Vleeshouwers, 1997).…”