Belowground response of a bahiagrass pasture to long-term elevated [CO2] and soil fertility management

Authors: Runion, George; Prior, Stephen - Steve; Torbert, Henry - Allen

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2024
Publication Date: 2/8/2024
Citation: Runion, G.B., Prior, S.A., Torbert III, H.A. 2024. Belowground response of a bahiagrass pasture to long-term elevated [CO2] and soil fertility management. Plants. 13(4):485. https://doi.org/10.3390/plants13040485.
DOI: https://doi.org/10.3390/plants13040485

Interpretive Summary: Increasing atmospheric CO2 concentration may impact agriculture. Effects of rising atmospheric CO2 on important pasture and grazing land systems remain far less studied than other crop and forest ecosystems. This study examined root growth of bahiagrass (Paspalum notatum Flüggé) exposed to ambient and elevated (ambient + 200 ppm) levels of atmospheric CO2 and two soil fertility conditions (managed and unmanaged). Across the 10-year study period, fertility additions increased both root length density (53.8%) and root weight density (68.2%) compared to unmanaged areas. Roots were generally unaffected by CO2. This long-term study suggests that Southern bahiagrass pasture root growth would not be greatly impacted by rising CO2 and that these pasture systems would benefit greatly from proper fertility management.

Technical Abstract: While the effects of rising atmospheric CO2 concentration [CO2] on pastures and grazing lands is beginning to receive research attention, these important systems remain far less studied than other agronomic and forest ecosystems. To help fill this knowledge gap, we conducted a long-term (2005-2015) study of bahiagrass (Paspalum notatum Flüggé) response to elevated [CO2] and fertility management. The study was conducted at the USDA-ARS open top field chamber facility at the National Soil Dynamics Laboratory in Auburn, AL. A newly established bahiagrass pasture was exposed to ambient or elevated (ambient + 200 µmol mol-1) [CO2]. Following one year for pasture establishment, half the plots received a fertilizer treatment [N [(NH4)2SO4] at 90 kg ha-1 three times yearly plus P, K, and lime as recommended by soil testing]; the remaining plots received no fertilization. These treatments were implemented to represent managed (M) and unmanaged (U) pastures which are both common in the Southeastern US. Root cores (0-60 cm depth) were collected annually in October and processed using standard procedures. Across the 10-year study period, fertility additions were consistent in increasing both root length density (53.8%) and root weight density (68.2%) compared to unmanaged plots. However, root measurement variables were generally unaffected by either [CO2] or its interaction with management. Study results suggest that Southern bahiagrass pastures could benefit greatly from fertilizer additions. However, results also suggest that bahiagrass pasture root growth is unlikely to be greatly affected by rising atmospheric [CO2], at least by those levels expect during this century.