Interference of onion growth by green foxtail (<i>Setaria viridis</i>(L.) Beauv.)

• Main Author: Englund, Patricia L.
• Other Authors: Ashford, Ross
• Format: Others
• Language: en
• Published: University of Saskatchewan 2012
• Online Access: http://library.usask.ca/theses/available/etd-08012012-093050/

<p>Very little experimental work was done in Saskatchewan before 1971 on the use of herbicides for weed control in irrigated vegetable crops. In 1970 a 2-acre demonstration block at Outlook, Saskatchewan revealed that onions (<i>Allium cepa</i> L.) would perform well in this area under irrigated conditions <Young-Zyi 1974). It was also shown that a severe weed problem existed with this crop. Recommended herbicides were unpredictable, depending largely upon soil type, moisture level and temperature.</p> <p>Green foxtail (<i>Setaria virldis</i>(L.) Beauv.) apparently offers very little competition in well-established cereal crops and therefore causes less concern to grain growers than vegetable growers. It was initially observed in field trials by D.H. Dabbs (1983) that green foxtail caused a "drastic reduction" in onion yields that could not be explained simply by the effects of competition. Effects were evident even at green foxtail densities as low as 2.5 plants/m². It did not appear logical that so few green foxtail plants could be inhibiting onion growth by straight competition for light, nutrients and water.</p> <p>Recent reports have stressed the need for additional research on the biology of specific weed-crop interactions (Chamblee .e.t .al. 1982; McWhorter and Shaw 1982; Schweizer and Bridge 1982). They point out that information provided by such research would be useful in establishing guidelines for specific systems of integrated weed management.</p> <p>Based on these observations and ideas, it was hypothesized that green foxtail inhibits onion growth allelopathically. At present, the literature indicates that approximately 50 weed species throughout the world may possess allelopathic properties.</p> <p>Field, growth chamber and laboratory studies were initiated in an effort to determine the extent to which green foxtail reduces the growth of onions and secondly) to determine if green foxtail plants possess a chemical that inhibits developing onion plants. Experiments attempted to separate competitive effects of green foxtail on onion from noncompetitive Callelopathic) effects. A third objective was to establish if any cultivar differences exist in the response of onions to the presence of green foxtail.</p>