Nitrogen rhizodeposition of young wheat plants under elevated CO2 and drought stress

The objective of this study was to determine the effect of drought stress and elevated CO2 concentrations around the shoots on N rhizodeposition of young wheat plants. In a pot experiment, the plant N pool was labeled through (NH3)-N-15 application to shoots at nontoxic NH3 concentrations, and the impact of low water supply (40% field capacity), elevated CO2 (720 mu mol mol(-1) CO2), and the combination of both factors on the N-15 distribution was studied. Total N-15 rhizodeposition ranged from 5 to 11% of the total N-15 recovered in the plant/soil system. Elevated CO2 concentration as well as drought stress increased the belowground transport of N and increased the relative portion of N rhizodeposition on total N-15 in the plant/soil system. However, while the increased N rhizodeposition with elevated CO2 was the result of increased total belowground N transport, drought stress additionally increased the portion of N-15 found in rhizodeposition vs roots. Elevated CO2 intensified the effect of drought stress. The percentage of water soluble N-15 in the N-15 rhizodeposition was very low under all treatments, and it was significantly decreased by the drought-stressed treatments.