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Evaluating shade cloth to simulate Palmer amaranth (Amaranthus palmeri) competition in sweetpotato

Published online by Cambridge University Press:  22 March 2021

Levi D. Moore*
Graduate Student, Department of Horticultural Science, North Carolina State University, Raleigh, NC, USA
Katherine M. Jennings
Associate Professor, Department of Horticultural Science, North Carolina State University, Raleigh, NC, USA
David W. Monks
Professor, Department of Horticultural Science, North Carolina State University, Raleigh, NC, USA
David L. Jordan
Professor, Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, USA
Ramon G. Leon
Associate Professor, Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, USA
Michael D. Boyette
Professor, Department of Biological and Agricultural Engineering, North Carolina State University, Raleigh, NC, USA
Author for correspondence: Levi D. Moore, Department of Horticultural Science, North Carolina State University, 2721 Founders Drive, Raleigh, NC27965. (Email:


Field studies were conducted in 2019 and 2020 to compare the effects of shade cloth light interception and Palmer amaranth (Amaranthus palmeri S. Watson) competition on ‘Covington’ sweetpotato [Ipomoea batatas (L.) Lam.]. Treatments consisted of a seven by two factorial arrangement, in which the first factor included shade cloth with an average measured light interception of 41%, 59%, 76%, and 94% and A. palmeri thinned to 0.6 or 3.1 plants m−2 or a nontreated weed-free check; and the second factor included shade cloth or A. palmeri removal timing at 6 or 10 wk after planting (WAP). Amaranthus palmeri light interception peaked around 710 to 840 growing degree days (base 10 C) (6 to 7 WAP) with a maximum light interception of 67% and 84% for the 0.6 and 3.1 plants m−2 densities, respectively. Increasing shade cloth light interception by 1% linearly increased yield loss by 1% for No. 1, jumbo, and total yield. Yield loss increased by 36%, 23%, and 35% as shade cloth removal was delayed from 6 to 10 WAP for No. 1, jumbo, and total yield, respectively. F-tests comparing reduced versus full models of yield loss provided no evidence that the presence of yield loss from A. palmeri light interception caused yield loss different than that explained by the shade cloth at similar light-interception levels. Results indicate that shade cloth structures could be used to simulate Covington sweetpotato yield loss from A. palmeri competition, and light interception could be used as a predictor for expected yield loss from A. palmeri competition.

Research Article
© The Author(s), 2021. Published by Cambridge University Press on behalf of the Weed Science Society of America

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Associate Editor: Martin M. Williams II, USDA–ARS


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