EFFECTS OF CARBON-DIOXIDE ENRICHMENT ON COTTON NUTRIENT DYNAMICS

The rise in atmospheric carbon dioxide (CO2) concentration is predicte d to have positive effects on agro-ecosystem productivity. However, an area which requires further study centers on nutrient dynamics of cro ps grown under elevated CO2 in the field. In 1989 and 1990, cotton [Go ssypium hirsutum (L.) Deltapine 77'] was grown under two CO2 levels [3 70 mu mol mol(-1)=ambient and 550 mu mol mol(-1)=free-air CO2 enrichme nt(FACE)]. At physiological maturity, nutrient concentration and conte nt of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magne sium (Mg), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) were determined for whole plant and individual plant organs. While the effe cts of added CO2 on whole plant nutrient concentrations and contents w ere consistent, some differences among plant organs were observed betw een years. FACE often decreased tissue nutrient concentration, but inc reased total nutrient accumulation. Results indicate that under elevat ed CO2, field grown cotton was more nutrient efficient in terms of nut rient retrieval from the soil and nutrient utilization in the plant. T his implies more efficient fertilizer utilization, better economic ret urn for fertilizer expenditures, and reduced environmental impact from agricultural fertilization practices in the future.