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Title: Influences of rising atmospheric carbon dioxide and ozone concentrations on soil respiration, soil microbial biomass, nutrient availability and soil C dynamics in a soybean-wheat no-till system

Author
item Booker, Fitzgerald
item CHENG, LEI - North Carolina State University
item Burkey, Kent
item Fiscus, Edwin
item HU, SHUIJIN - North Carolina State University

Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 5/30/2009
Publication Date: 5/30/2009
Citation: Booker, F.L., Cheng, L., Burkey, K.O., Fiscus, E.L., Hu, S. 2009. Influences of rising atmospheric carbon dioxide and ozone concentrations on soil respiration, soil microbial biomass, nutrient availability and soil C dynamics in a soybean-wheat no-till system. American Society of Agronomy Meetings.

Interpretive Summary: N/A

Technical Abstract: Effects of the elevated carbon dioxide and ozone on agroecosystems include effects on root growth, soil microbiology and soil C dynamics although the combined effects of these gases on belowground processes have been little studied. The objective of this experiment was to determine the separate and combined effects of elevated carbon dioxide and ozone on soil respiration, microbial biomass, nutrient availability and soil C levels. Plants were treated with either ambient or elevated carbon dioxide (550 µmol mol-1) in combination with charcoal-filtered (CF) air or CF air plus ozone (1.4 x ambient ozone) using open-top field chambers. Soil respiration during three growing seasons was stimulated by 26% with elevated carbon dioxide and suppressed by ozone during soybean reproductive growth, possibly due to early root senescence. Microbial soil respiration was also higher with elevated carbon dioxide but similar to the control in the added ozone treatment. There were no treatment effects on microbial biomass C. Availability of soil cations (Ca and Mg) was increased with elevated carbon dioxide while ammonia availability was lower in the added ozone treatment. Delta 13C values of the coarse organic matter fraction decreased with elevated carbon dioxide while percent C marginally increased. In combination, elevated ozone attenuated the effect of elevated carbon dioxide on soil respiration and percent C, suggesting that C sequestration potential for soybean-wheat no-till systems could be curtailed by rising tropospheric ozone concentrations.