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Title: CROP RESIDUE DECOMPOSITION AS AFFECTED BY GROWTH UNDER ELEVATED ATMOSPHERICCO2

Author
item Torbert, Henry - Allen
item Prior, Stephen - Steve
item Rogers Jr, Hugo
item RUNION, G. - FORESTRY SCHOOL AUBURN AL

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Scientist have detected an increasing global concentration of CO2 in the atmosphere largely from the use of fossil fuels, such as gasoline. This increase has led to concerns regarding its potential effects on the environment, such as the possibility of global warming. A highly debated hypothesis is that the increased levels of CO2 in the atmosphere is being removed by plants and is being stored in soil in the form of organic carbon. Understanding how CO2 is cycled is important if we are to determine its potential impact to the environment. This study examined how plants grown under different levels of atmospheric CO2 decomposed after they had died. The data from this study indicated that there is a potential for carbon from atmospheric CO2 to be stored in soil under agriculture production systems, but the potential storage of carbon may be different for different crop species. The findings of this study demonstrate the importance of further research for developing mitigation strategies for global change based upon wise management practices.

Technical Abstract: Increasing global CO2 level has led to concerns about process changes in the biosphere. Elevated atmospheric CO2 has been shown to increase plant biomass resulting in greater amounts of residue returned to soil. However, he effects on the long-term storage of C in soil are highly debated. Changes in both quantity and quality of plant residue as well as residue management may alter soil C and N dynamics. Plant residues were collected from an experiment with increased CO2 levels under field conditions. A soil incubation study was conducted in a Blanton loamy sand (loamy siliceou thermic, Grossarenic Paleudults)to examine the effect of two crop species soybean, Glycine max (L.) Merr. and grain sorghum, Sorghum bicolor (L.) Moench) grown at two CO2 concentrations (ambient and twice ambient),and two simulated tillage treatments (till or no-till) on potential Cand N minera- lization. Difference in biomass inputs between plants grown in ambient an elevated atmospheric CO2 was also considered. Tillage reduced inorganic N content but had no effect on C mineralization. Both inorganic N content and C mineralization were higher with soybean compared to grain sorghum. While changes due to elevated CO2 concentration to both plant residue quality and quantity affect C cycling,residue quality may be more important for determining C storage. Nitrogen cycling in soil may be a controlling factor for C storage in terrestrial ecosystems.