Nitrogen dynamics under elevated carbon dioxide

By 2070, atmospheric carbon dioxide (CO₂) concentration is expected to double that observed in 1950. In this higher CO₂ world, the sustainability of global crop production may be in jeopardy unless current N management strategies are changed. Many studies have tried to quantify the effect of increased CO₂ on plant production and N utilization, but the results have generally been inconclusive and contradictory. To interpret the available information and provide new insight on crop management in the near future, we examined the effects of elevated CO₂ on N dynamics in grain crop and legume pasture systems using meta-analytic techniques (366 observations from 127 studies).

The analysis revealed that elevated CO₂ increases crop production. However, to achieve this increase, an adequate supply of N, derived from soil, fertilizer and/or biological N-fixation is required. Since N demand and removal in many grain cropping systems is predicted to increase under future CO₂-enriched environments, current N management practices need to be revised. These practices may include higher rates of fertilizer N application, greater use of legume intercropping, or legume cover crops, etc. ANZ-04