Submitted to: Global Change Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/31/2005
Publication Date: 4/5/2005
Citation: Prior, S.A., Runion, G.B., Rogers Jr, H.H., Torbert III, H.A., Reeves, D.W. 2005. Elevated atmospheric co2 effects on biomass production and soil carbon in conventional and conservation cropping systems. Global Change Biology. 11:657-665. Interpretive Summary: Increased CO2 in the atmosphere has led to concerns regarding potential environmental changes and how crops will be managed. We studied how elevated CO2 would affect crop production and soil C storage under conventional and conservation management. Cover crop residues were increased by high CO2 in conservation systems. But, the variable response of weeds to CO2 in the conventional system suggest more work is required to clarify management implications. Rising CO2 levels will increase soybean residue more than that of sorghum regardless of management systems used. Yield will be increased (due to high CO2) for soybean followed by wheat and sorghum. Total residue production was increased by high CO2 and conservation management. This resulted in increased soil carbon in the soil profile, suggesting that in a future elevated CO2 world, agroecosystems could store more C, especially with conservation management. Results also suggest that with conservation management in a high CO2 environment, more crop residue will increase ground cover thereby improving water infiltration and soil water storage, and reducing soil erosion.
Technical Abstract: Increasing atmospheric CO2 concentration has led to concerns about potential effects on production agriculture as well as agriculture's role in sequestering C. In the fall of 1997, a study was initiated to compare the response of two crop management systems (conventional and conservation) to elevated CO2. The study used a split-plot design replicated three times with two management systems as main plots and two CO2 levels (ambient and twice ambient) as subplots using open top chambers on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudults). The conventional system was a grain sorghum [Sorghum bicolor (L.) Moench.] and soybean [Glycine max (L.) Merr.] rotation with winter fallow and spring tillage practices. In the conservation system, sorghum and soybean were rotated and three cover crops were used [crimson clover (Trifolium incarnatum L.), sunn hemp (Crotalaria juncea L.), and wheat (Triticum aestivum L.)] under no-tillage practices. The effect of management on soil C and biomass responses over two cropping cycles (four years) were evaluated. In the conservation system, cover crop residue (clover, sunn hemp, and wheat) was increased by high CO2, but CO2 effects on weed residue were variable in the conventional system. Elevated CO2 had a greater effect on increasing soybean residue as compared to sorghum, and grain yield increases were greater for soybean followed by wheat and sorghum. Differences in sorghum and soybean residue production within the different management systems were small and variable. Cumulative residue inputs were increased by elevated CO2 and conservation management. Greater inputs resulted in a substantial increase in soil C concentration at the 0-5 cm depth increment in the conservation system under CO2-enriched conditions. Smaller shifts in soil C were noted at greater depths (5-10 and 15-30 cm) due to management or CO2 level. Results suggest that with conservation management in a high CO2 environment, greater residue amounts could increase soil C storage as well as increase ground cover.