Effect of elevated carbon dioxide on N-fertilizer recovery under wheat in Australia

摘要

The effect of elevated [CO_2] on the recovery of ~(15)N-labeled urea by wheat was investigated under ambient (380 umol/mol) and elevated (550 umol/mol) [CO_2] at the Free-Air Carbon dioxide Enrichment (FACE) experiment in western Victoria, Australia.~(15)N-enriched (c. 10% atom excess) granular urea was applied to PVC microplots at 50 kg N/ha at rainfed and irrigated condition and two times of sowing. At physiological maturity, total biomass was increased by 23% under elevated [CO_2], as a result ofa 25% and 22% increase in stem and root biomass, respectively, but not grain yield. Total N uptake of wheat was increased by 17% under elevated [CO_2], irrespective of irrigation and sowing time. Elevated [CO2] increased grain C/N ratio by 11% only under irrigation, but not for stem and root. Elevated [CO_2] had no significant effect on percentage of N derived from fertilizer (%Ndff) for grain, stem and root but irrigation increased %Ndff for all wheat parts only in late sowing. Elevated [CO_2] did notalter the percentage of ~(15)N recovered in grain, stem and root, but marginally increased the total recovery by 30% at late sowing time under irrigation. There were no significant effects of elevated [CO_2] on ~(15)N recoveries in soil and total fertilizer N losses, indicating potentially similar availability of fertilizer N residues to subsequent crops in the longer term.