- • The effects of elevated CO2 are reported here on the uptake of nitrogen (N) and its relationships with growth and grain yield in rice (Oryza sativa).
- • Using free-air CO2 enrichment (FACE), rice crops were grown at ambient or elevated (c. 300 µmol mol−1 above ambient) CO2 and supplied with low, medium or high levels of N.
- • For the medium and high N treatments, FACE increased N uptake at panicle initiation but not at maturity. For total dry matter, as well as spikelet number and grain yield, positive interactions between CO2 and N uptake were observed. Furthermore, spikelet number was closely associated with N uptake at panicle initiation.
- • These results indicate that, to maximize rice grain yield under elevated CO2, it is important to supply sufficient N over the whole season, in order to maintain the enhancement in dry matter production. In addition, N availability must be coordinated with the developmental stage of the crop, specifically to ensure that sufficient N is available at panicle initiation in order to maximize spikelet number and grain yield.