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Nitrogen demand and the recovery of 15N-labelled fertilizer in wheat grown under elevated carbon dioxide in southern Australia

Lam, Shu Kee, Chen, Deli, Norton, Rob, Armstrong, Roger
Nutrient cycling in agroecosystems 2012 v.92 no.2 pp. 133-144
Triticum aestivum, carbon dioxide, grain yield, irrigation, nitrogen, nitrogen content, nitrogen fertilizers, rain, soil, sowing, spring wheat, urea, Australia
There are few reports on the effects of atmospheric carbon dioxide concentration ([CO2]) on fertilizer N recovery by crops under open-air conditions. This study was conducted at the Australian Grains Free-Air CO2 Enrichment (AGFACE) facility in southern Australia to investigate the effects of elevated [CO2] (550 μmol mol−1) on growth, N uptake and fertilizer 15N recovery by spring wheat (Triticum aestivum L. cv. Yitpi) over a 2-year period. 15N-enriched (10.22 atom%) granular urea was applied to microplots at 50 kg N ha−1 at varying seasonal rainfall and temperature scenarios (simulated by supplementary irrigation and late sowing) for three experimental periods [2008 normal sowing (2008NS), 2008 late sowing (2008LS) and 2009 normal sowing (2009NS)]. Elevated [CO2] increased wheat biomass (27–58%), N uptake (18–44%) and amount of plant N derived from soil (20–50%) at 2008NS and 2009NS (rainfed), but the effect was not apparent at 2008LS (hotter and drier) and supplementary irrigated plots for 2009NS (above-average rainfall). Tissue N concentration and N derived from fertilizer were unaffected by elevated [CO2] in any experimental period. Irrespective of [CO2], grain yield and whole plant fertilizer N uptake was 37–94 and 13–609%, respectively, higher under supplementary irrigated plots than that in rainfed counterparts. These results indicate that more fertilizer N will need to be applied to this wheat production zone under future [CO2] environments, and yield gains in hotter and drier climates will be lower than those in higher rainfall zones.