Author: Ziska, Lewis H.

Source: Global Change Biology, Volume 6, Number 8, December 2000 , pp. 899-905(7)

Publisher: Wiley-Blackwell

Abstract:

Summary

Soybean (Glycine max) was grown at ambient and enhanced carbon dioxide (CO₂, + 250 μL L⁻¹ above ambient) with and without the presence of a C3 weed (lambsquarters, Chenopodium album L.) and a C4 weed (redroot pigweed, Amaranthus retroflexus L.), in order to evaluate the impact of rising atmospheric carbon dioxide concentration [CO₂] on crop production losses due to weeds. Weeds of a given species were sown at a density of two per metre of row. A significant reduction in soybean seed yield was observed with either weed species relative to the weed-free control at either [CO₂]. However, for lambsquarters the reduction in soybean seed yield relative to the weed-free condition increased from 28 to 39% as CO₂ increased, with a 65% increase in the average dry weight of lambsquarters at enhanced [CO₂]. Conversely, for pigweed, soybean seed yield losses diminished with increasing [CO₂] from 45 to 30%, with no change in the average dry weight of pigweed. In a weed-free environment, elevated [CO₂] resulted in a significant increase in vegetative dry weight and seed yield at maturity for soybean (33 and 24%, respectively) compared to the ambient CO₂ condition. Interestingly, the presence of either weed negated the ability of soybean to respond either vegetatively or reproductively to enhanced [CO₂]. Results from this experiment suggest: (i) that rising [CO₂] could alter current yield losses associated with competition from weeds; and (ii) that weed control will be crucial in realizing any potential increase in economic yield of agronomic crops such as soybean as atmospheric [CO₂] increases.

Keywords: carbon dioxide; climate change; competition; lambsquarters; pigweed; yield

Document Type: Commentary

DOI: http://dx.doi.org/10.1046/j.1365-2486.2000.00364.x

Affiliations: 1: Climate Stress Laboratory, Bldg 046 A, USDA-ARS, 10300 Baltimore Avenue, Beltsville, MD 20705, USA

Publication date: 2000-12-01

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