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Title: NITROGEN FERTILIZATION AFFECTS BAHIAGRASS RESPONSE TO ELEVATED ATMOSPHERIC CO2

Author
item NEWMAN, Y - UNIV OF FLORIDA
item SOLLENBERGER, L - UNIV OF FLORIDA
item BOOTE, K - UNIV OF FLORIDA
item Allen Jr, Leon
item THOMAS, J - UNIV OF FLORIDA
item LITTELL, R - UNIV OF FLORIDA

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2005
Publication Date: 4/1/2006
Citation: Newman, Y.C., Sollenberger, L.E., Boote, K.J., Allen Jr, L.H., Thomas, J.M., Littell, R.C. 2006. Nitrogen fertilization affects bahiagrass response to elevated atmospheric carbon dioxide. Agronomy Journal. 98:382-387.

Interpretive Summary: Nitrogen (N) fertilization could affect the forage yield and nutritive value of grasses under future predicted climate changes of increasing atmospheric carbon dioxide (CO2) and potential global warming. USDA-ARS and University of Florida scientists measured yield of forage dry matter (DM), crude protein (CP), and in vivo digestible organic matter (IVDOM) of bahiagrass, an important Southeastern USA pasture and hay crop. Bahiagrass was grown at high and low N fertilizer rates (80 and 320 pounds of N per acre), two CO2 concentrations (360 and 700 ppm), and four temperatures (Gainesville ambient and +2.7, +5.4, and +8.1 degrees Fahrenheit above ambient). Yields of DM increased with increasing CO2 at high N but not at low N. Increasing temperature had a large positive effect on DM yield at low N (23%) and a smaller effect at high N (9%). Nutritive value (CP and IVDOM) of bahiagrass increased at the high N fertilizer rate, but was not affected by CO2 or temperature. They concluded that status of N in bahiagrass affected DM yield response to elevated CO2 and, although greater N rate increased bahiagrass nutritive value, it did not affect nutritive value responses to CO2 or temperature.

Technical Abstract: Plant nitrogen status may affect the response of grasses to the impact of rising carbon dioxide (CO2) and elevated temperature. The objectives were to determine the effects of nitrogen (N) fertilization rates on yield and nutritive value of bahiagrass (BG), Paspalum notatum Flugge, grown in elevated temperatures and CO2. Annual total herbage dry matter (DM) yield, harvested N, in vitro digestible organic matter (IVDOM), and crude protein (CP) concentrations were determined for herbage of plants grown at 80 or 320 kg of N per ha applied annually during two years in two levels of CO2 (360 and 700 ppm) and four temperatures in temperature-gradient greenhouses (baseline, or 'ambient' temperature, B; B + 1.5; B + 3.0; and B + 4.5 Celsius). Yields of DM increased with increasing CO2 at high N but not at low N, and total N harvested followed a similar trend. Increasing temperature had a positive effect on DM yield at low N (23%) and at high N (9%). Nutritive value of BG increased at the high N rate, but was not affected by CO2 or temperature. Status of N in BG affected DM yield response to elevated CO2 and, although greater N rate increased BG nutritive value, it did not affect nutritive value responses to CO2 or temperature.