Submitted to: Environmental Management
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/18/2003
Publication Date: 7/15/2004
Citation: Prior, S.A., Torbert III, H.A., Runion, G.B., Rogers Jr, H.H. 2004. Elevated atmospheric co2 in agroecosystems: residue decomposition in the field. Environmental Management. 33(1):s344-s354 Interpretive Summary: Results from this study demonstrate that residue production can be expected to increase in a CO2-enriched environment. Decomposition of this high CO2 residue will likely follow patterns similar to those for ambient CO2 produced material. The greater production under high CO2 resulted in more residue remaining after overwintering. The effect of CO2 on aboveground residue remaining will be greater for soybean, while positive effects of CO2 on remaining root residue will be similar for soybean and sorghum. This additional crop residue may lead to an increase in soil quality and protection of soil resources (especially if highly erodible). In a high CO2 world, greater amounts of crop residue could increase soil carbon, ground cover, and promote favorable soil physical characteristics which could increase soil water holding capacity and reduce erosion.
Technical Abstract: Elevated atmospheric CO2 concentration can increase biomass production and alter tissue composition. Shifts in both quantity and quality of crop residue may alter carbon (C) and nitrogen (N) dynamics and management considerations in future CO2-enriched agroecosystems. This study was conducted to determine decomposition rates of the legume soybean [Glycine max (L.) Merr.] and non-legume grain sorghum [Sorghum bicolor (L.) Moench.] residue produced under two levels of atmospheric CO2 (ambient and twice ambient) on a Blanton loamy sand (loamy siliceous, thermic, Grossarenic Paleudults) in Auburn, Alabama, managed using no-till practices. At maturity, harvested plants were separated into component parts for dry weight determination and tissue analysis. Mass, C, and N losses from residues were determined using the mesh bag method. Biomass production was significantly greater for soybean compared to sorghum and for elevated versus ambient CO2-grown plants. The CO2 level had little affect on the C:N ratio of residue (probably because the tissue used was senesced). Elevated CO2 concentration did not affect percent residue recovery; however, greater biomass production observed under elevated CO2 resulted in more residue and C remaining after overwintering. The higher total N content of soybean residue, particularly when grown under elevated CO2, indicated more N may be available to a following crop with lower N inputs required. Results suggest that in a high CO2 environment, greater amounts of residue may increase soil C and ground cover, which may enhance soil water storage, improve soil physical properties, and reduce erosion losses.