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1 November 2003 Effects of shading on common waterhemp (Amaranthus rudis) growth and development
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Common waterhemp is a significant weed problem in Midwestern cropping systems partly because of its potential for multiple emergence events during the growing season. The effects of shade and time of emergence on this weed have not been characterized. In the field, common waterhemp vegetative and reproductive growth were evaluated under different irradiance levels at two emergence times. In full sunlight a common waterhemp plant emerging in late May produced 720 g of biomass and over one million seeds, and a plant emerging in late June produced 350 g of biomass and over 730,000 seeds. Plant biomass and seed production were lower as irradiance levels were decreased to 40, 68, and 99% shade. Mortality was high for common waterhemp grown in 99% shade; however, surviving plants produced some viable seed. Common waterhemp plants grown under reduced irradiance had higher leaf area ratios and lower relative growth rates.

Nomenclature: Common waterhemp, Amaranthus rudis Sauer AMATA.

Lawrence E. Steckel, Christy L. Sprague, Aaron G. Hager, F. William Simmons, and German A. Bollero "Effects of shading on common waterhemp (Amaranthus rudis) growth and development," Weed Science 51(6), 898-903, (1 November 2003).
Received: 3 October 2002; Accepted: 1 April 2003; Published: 1 November 2003

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