Effects of Elevated Atmospheric CO2 and N Fertilization on Bahiagrass Root Distribution.

The effects of elevated atmospheric CO2 on pasture systems remain understudied in the Southeastern US. A 10-year study of bahiagrass (Paspalum notatum Flüggé) response to elevated CO2 was established in 2005 using open top field chambers on a Blanton loamy sand (loamy siliceous, thermic, Grossarenic Paleudults). Plants were subjected to ambient or elevated (ambient plus 200 ppm) CO2. After a year establishment period, N was applied to half of the plots ([(NH4)2SO4] at 90 kg/ha 3x/yr) while the remaining plots received no N fertilization. These two treatments represent managed and unmanaged pastures, both of which are common in the Southeast. Root length and dry weight densities were evaluated yearly in 5 cm increments to a depth of 60 cm. In general, there was very little effect of elevated CO2 on root variables. However, roots showed a strong response to N addition. Findings suggest that bahiagrass pasture root productivity will be responsive to N fertilization, but will not be greatly affected by rising atmospheric CO2.