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Interference of Annual Weeds in Seedling Alfalfa (Medicago sativa)

Published online by Cambridge University Press:  12 June 2017

Albert J. Fischer ,
Jean H. Dawson  and
Arnold P. Appleby
Albert J. Fischer
Affiliation:
Dep. Crop Sci., Oregon State Univ., Corvallis, OR 97331
Jean H. Dawson
Affiliation:
Dep. Crop Sci., Oregon State Univ., Corvallis, OR 97331
Arnold P. Appleby
Affiliation:
U.S. Dep. Agric, Irrigated Agric. Res. and Ext. Ctr., Prosser, WA 99350
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Abstract

Barnyardgrass [Echinochloa crus-galli (L.) Beauv. #4 ECHCG] and pigweeds (mixture of Amaranthus retroflexus L. # AMARE and A. powellii S. Wats. # AMAPO) seeded separately with alfalfa (Medicago sativa L.) in mid-August suppressed alfalfa severely before frost killed them in October and November. Some alfalfa was killed, and yield of alfalfa forage was reduced in each of three harvests the following year. These weeds did not harm alfalfa seeded in mid-September. Downy brome (Bromus tectorum L. # BROTE) and tumble mustard (Sisymbrium altissimum L. # SSYAL) suppressed alfalfa seeded in August and September. They reduced alfalfa stands and reduced yield of alfalfa forage in each of three harvests the following year. Alfalfa seeded August 27 and allowed to compete with a mixture of these species for various periods was injured most by weeds that emerged with the alfalfa and remained uncontrolled until forage harvest in May. These weeds did not reduce alfalfa yields if removed by 36 days after alfalfa emergence. Thereafter, yield decreased as the period of weed interference increased. Interference was most damaging in early spring, when growth of winter annual weeds was rapid and vigorous. Weeds seeded 65 or more days after alfalfa emergence did not reduce alfalfa yields but sometimes produced enough biomass to reduce the quality of the first-cutting alfalfa hay.

Keywords

CompetitionAmaranthus retroflexusA. powelliiBromus tectorumEchinochloa crus-galliSisymbrium altissimumAMAPOAMAREBROTEECHCGSSYAL
Type
Weed Biology and Ecology
Information
Weed Science , Volume 36 , Issue 5 , September 1988 , pp. 583 - 588
Copyright
Copyright © 1988 by the Weed Science Society of America 

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References

Literature Cited

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