Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 8, 2005
Publication Date: July 1, 2006
Citation: Prior, S.A., Torbert III, H.A., Runion, G.B., Rogers Jr, H.H., Ort, D.R., Nelson, R.L. 2006. Free-air carbon dioxide enrichment of soybean: Influence of crop variety on residue decomposition. Journal of Environmental Quality. 35:1470-1477. Interpretive Summary: The increasing level of CO2 in the atmosphere has led to concerns regarding potential changes in the global environment. Elevated CO2 can lead to changes in crop residue quality, but it is not known if this is true for all soybean varieties. . Such knowledge is needed to help predict how the breakdown of crop residues will impact carbon and nitrogen cycling in farm soils. Ours results showed that soybean variety selection will have a greater influenced on nitrogen cycling in soil under elevated CO2 conditions. The breakdown of residues of some soybean varieties may result in more plant available N in soil in a high CO2 world.
Technical Abstract: Elevated atmospheric CO2 can result in larger plants returning greater amounts of residues to the soil. However, the effects of elevated CO2 on carbon (C) and nitrogen (N) cycling for different soybean varieties has not been examined. Aboveground residue of eight soybean varieties (Glycine max [L.] Merr.) was collected from a field study where crops had been grown under two different atmospheric CO2 levels [370 µmol/mol(ambient) and 370 µmol/mol (free-air carbon dioxide enrichment) (FACE)]. Senesced residue material was used in a 60 day laboratory incubation study to evaluate potential C and N mineralization. Residue N concentration was usually increased by FACE, but residue C concentration was not altered. Varietal differences were observed with the oldest variety having the lowest residue N concentration and highest residue C:N ratio. Residue C:N ratio was lower under FACE which could be attributed to increased N fixation. Mineralized N was usually increased by FACE, except for a non-nodulating variety, suggesting that increased N fixation impacted residue decomposition. Mineralized N was lowest in the oldest variety, illustrating the influence of high residue C:N ratio. Across varieties, mineralized C was increased slightly by FACE, however, differences in varieties suggest that the impact of elevated CO2 on N mineralization could be influenced by soybean variety selection.