| Abstract: | SUMMARY Increasing atmospheric CO2 concentrations CO2] have the potential to enhance growth and yield of agricultural plants. Con-comitantly plants grown under high CO2] show significant changes of the chemical composition of their foliage and of other plant parts. Particularly, high CO2] result in a decrease of plant nitrogen (N) concentration, which may have serious consequences for crop quality. This presentation summarizes the results of a variety of CO2 enrichment studies with pasture plants (Lolium spp., Trifolium repens) and cereal species (Triticum aestivum, Hordeum vulgare) which were conducted at our laboratory under different growth and CO2 exposure conditions ranging from controlled environment studies to investigations under free air carbon dioxide enrichment (FACE). With the exception of clover in all experiments a CO2-induced decline of forage and grain N concentration was observed. The magnitude of this reduction differed between species, cultivars, management conditions (N fertilization) and CO2 exposure conditions. No unambiguous evidence was obtained whether N fertilization can contribute to meet the quality requirements for cereals and grass monocultures with respect to tissue N concentrations in a future high-CO2 world. As shown in the FACE experiments current application rates of N fertilizers are inadequate to achieve quality standards. |
