Tillage and wind effects on soil CO concentrations in muck soils

摘要

Rising atmospheric carbon dioxide (CO) concentrations from agricultural activities prompted the need to quantify greenhouse gas emissions to better understand carbon (C) cycling and its role in environmental quality. The specific objective of this work was to determine the effect of no-tillage, deep plowing and wind speeds on the soil CO concentration in muck (organic) soils of the Florida Everglades. Miniature infrared gas analyzers were installed at 30cm and recorded every 15min in muck soil plowed with the Harrell Switch Plow (HSP) to 41cm and in soil Not Tilled (NT), i.e., not plowed in last 9 months. The soil CO concentration exhibited temporal dynamics independent of barometric pressure fluctuations. Loosening the soil resulted in a very rapid decline in CO concentration as a result of wind-induced gas exchange from the soil surface. Higher wind speeds during mid-day resulted in a more rapid loss of CO from the HSP than from the NT plots. The subtle trend in the NT plots was similar, but lower in magnitude. Tillage-induced change in soil air porosity enabled wind speed to affect the gas exchange and soil CO concentration at 30cm, literally drawing the CO out of the soil resulting in a rapid decline in the CO concentration, indicating more rapid soil carbon loss with tillage. At the end of the study, CO concentrations in the NT plots averaged about 3.3% while that in the plowed plots was about 1.4%. Wind and associated aerodynamic pressure fluctuations affect gas exchange from soils, especially tilled muck soils with low bulk densities and high soil air porosity following tillage.