Nitrogen Fertilization Affects Bahiagrass Responses to Elevated Atmospheric Carbon Dioxide

Increased atmospheric CO 2 and temperature typically lead to greater DM (dry matter) production of grassland plants; however, limited plant N may reduce this response. A 2‐yr study (1998–1999) was conducted to evaluate the effects and interactions among atmospheric CO 2 , temperature, and N fertilization rate on yield and nutritive value of ‘Pensacola’ bahiagrass ( Paspalum notatum Flügge). Bahiagrass was field grown in Millhopper fine sand (loamy, siliceous Grossarenic Paleudult) under greenhouses with controlled atmospheric CO 2 and temperature. Atmospheric CO 2 levels were 360 and 700 μmol mol −1 , and temperatures were B (baseline, corresponding to ambient in the greenhouse), B + 1.5°C, B + 3.0°C, and B + 4.5°C. Bahiagrass was fertilized at 80 kg N ha −1 (BG‐80) or 320 kg N ha −1 (BG‐320). Dry matter yield for BG‐80 remained the same regardless of CO 2 level (7.5 and 6.3 Mg ha −1 in Years 1 and 2), but BG‐320 DM yield increased with increasing CO 2 concentration in three of four harvests in Year 1 and from 14.8 to 17.3 Mg ha −1 in Year 2. Total N harvested response followed a similar trend as DM yield. Increasing temperature from B to B + 4.5°C had a positive effect on DM yield of BG‐80 (23%) and a lesser positive effect on BG‐320 (9% increase). Bahiagrass nutritive value increased due to greater N fertilization, but elevated CO 2 concentration and temperature had no effect. Nitrogen fertilization affected bahiagrass DM yield response to CO 2 , but not the nutritive value response to elevated atmospheric CO 2 or temperature.