Effects of carbon dioxide enrichment on cotton nutrient dynamics

The rise in atmospheric carbon dioxide (CO₂) concentration is predicted to have positive effects on agro‐ecosystem productivity. However, an area which requires further study centers on nutrient dynamics of crops grown under elevated CO₂ in the field. In 1989 and 1990, cotton Gossypium hirsutum (L.) ‘Deltapine 77'] was grown under two CO₂ levels 370 umol mol^‐1=ambient and 550 μmol mor^‐1=free‐air CO₂ enrichment (FACE)]. At physiological maturity, nutrient concentration and content of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) were determined for whole plant and individual plant organs. While the effects of added CO₂ on whole plant nutrient concentrations and contents were consistent, some differences among plant organs were observed between years. FACE often decreased tissue nutrient concentration, but increased total nutrient accumulation. Results indicate that under elevated CO₂, field grown cotton was more nutrient efficient in terms of nutrient retrieval from the soil and nutrient utilization in the plant. This implies more efficient fertilizer utilization, better economic return for fertilizer expenditures, and reduced environmental impact from agricultural fertilization practices in the future.