Soil CO 2 , CH 4 , and N 2 O fluxes over and between tile drains on corn, soybean, and forage fields under tile drainage management

Controlled tile drainage (CTD) can benefit the environment and crop production. However, CTD has the potential to increase soil greenhouse gas (GHG: CO 2 , CH 4 , N 2 O) emissions by increasing soil water contents and elevating field water levels. A paired-field (CTD and uncontrolled tile drainage (UTD)) approach was used to compare soil GHG emissions for silt loam corn, soybean, and forage fields under CTD and UTD management in eastern Ontario, Canada during a drier and a wetter growing season. A total of five field pairs were examined. Soil GHG emissions directly over tile drains (OT) and between tile drains (BT) in the CTD fields were also assessed. Average soil GHG emissions did not significantly differ ( p > 0.05) for CTD and UTD field pairs, except for CO 2 emissions (greater emissions from UTD fields) among two field pairs studied (forage in the drier growing season and soybean in the wetter growing season), and N 2 O emissions from a soybean field pair in the wet growing season (greater emissions from CTD field). Significantly higher soil water contents in the UTD forage field may have augmented CO 2 fluxes there. There were some significantly higher N 2 O (in the wetter growing season) and CO 2 emissions (in both growing seasons) BT relative to OT locations in some fields; but these differences were not translated significantly to other BT and OT site comparisons. The wetter growing season examined resulted in greater average daily soil CO 2 fluxes overall, but similar CH 4 and N 2 O fluxes for soybean fields compared to soybean fields in the drier growing season. Overall, there were no spatially or temporally systematic differences in GHG emissions among CTD and UTD field pairs, or among BT and OT locations in CTD fields.