|CHENG, LEI - North Carolina State University|
|HU, SHUIJIN - North Carolina State University|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2012
Publication Date: N/A
Technical Abstract: Atmospheric carbon dioxide and ozone often have counteracting influences on many C3 crops depending on the concentration of the gases and sensitivity of the crop and variety, but effects of these gases on plant-soil processes are poorly understood. The objective of this six-year experiment was to determine the separate and combined effects of elevated carbon dioxide and ozone on soil respiration and carbon accumulation in a no-till soybean-wheat system. Plants were treated with either ambient or elevated carbon dioxide (550 ppm) in combination with charcoal-filtered (CF) air or CF air plus ozone (1.4 x ambient ozone) using open-top field chambers. Plant residue C and N inputs to the soil were increased by 20 to 30% by elevated carbon dioxide and decreased by 5% by ozone. Soybean fine root biomass was increased by 13% by carbon dioxide and inhibited by 42% by ozone. Wheat root biomass was not significantly altered. Soil respiration averaged across six growing seasons was stimulated by 33% with elevated carbon dioxide but the effect of ozone was not significant. Soil microbial respiration was stimulated by 19 to 31% by elevated carbon dioxide. Between 2005 and 2011, soil C and N in the 0-5 cm depth doubled in all treatments, while there was no significant change in C and N at 5-10 cm and 10-20 cm depths. There were no significant effects of elevated carbon dioxide or ozone on soil C or N concentrations except in the final year of the study when C levels in the control and ozone treatments declined. Apparently double-cropping and no-till contributed to increased soil C and N content while increased C and N inputs with elevated carbon dioxide stimulated decomposition. Ozone effects were null, suggesting that inhibited decomposition compensated for reduced residue inputs.