Free-air Carbon Dioxide Enrichment of Wheat: Soil Carbon and Nitrogen Dynamics
- S. A. Prior *,
- H. A. Torbert,
- G. B. Runion,
- H. H. Rogers,
- C. W. Wood,
- B. A. Kimball,
- R. L. LaMorte,
- P. J. Pinter and
- G. W. Wall
- U SDA-ARS National Soil Dynamics Laboratory, Box 3439, Auburn, AL 36831-3439;
U SDA-ARS Grassland, Soil and Water Research Laboratory, 808 East Blackland Rd.,Temple, TX 76502;
S chool of Forestry, Auburn University, Auburn, AL 36849;
D epartment of Agronomy and Soils, 202 Funchess Hall, Auburn University, Auburn, AL 36849-5412;
The predicted positive impact of elevated atmospheric carbon dioxide (CO2) concentration on crop biomass production suggests that more C will reach the soil. An aspect of soil C sequestration that requires further study is the effect of elevated CO2 on C and N dynamics; this relationship is the key to understanding potential long-term C storage in soil. Soil samples (0–5, 5–10, and 10–20 cm increments) were collected after 2 yr of wheat (Triticum aestirum L.) production under two CO2 levels [370 (ambient) and 550 µL L−1 (free-air CO2 enrichment)(FACE)] and two water treatments [100% of ET replaced (wet) and 50% of ET replaced (dry)] on a Trix clay loam [fine, loamy, mixed (calcareous), hyperthermic Typic Torrifluvents] at Maricopa, AZ. Organic C, total N, potential C and N mineralization, and C turnover were determined during a 60-d incubation study. Organic C content increased at all three soil depths under FACE and the total N content increased at the 5 to 10 and 10 to 20 cm depths. In general, increased N mineralization under dry conditions corresponded well with patterns of higher C mineralization and turnover. Nitrogen mineralization was unaffected by CO2 treatment, indicating that factors other than N may limit C mineralization and turnover. Soil respiration and C turnover patterns were not affected by CO2 treatment level at the 0 to 5 cm depth; however, these measures were lower under FACE at the lower depths. Soil respiration and C turnover at the 10 to 20 cm depth were increased by water stress under ambient CO2; these measures under both water levels for FACE were similar to the ambient CO2/wet treatment, suggesting that more C storage in wheat cropping systems is likely under elevated CO2 regardless of water treatment.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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