Nitrous Oxide Emissions in Soybean Fields with Differential Drainage in Poorly Drained Soils in Minnesota.

The objective of this research was to quantify in-season N₂O emissions in soybean fields under tile-drainage and natural drainage (no tile). The study was set up in a split-plot arrangement in a randomized complete-block design with four replications, with drainage as whole plot (drained and undrained) and N treatment applied on the corn phase of the rotation as split plot (control, single and split-N application). Soil-to-atmosphere N₂O fluxes were measured using the non-steady state chamber method. During 2015, undrained soils had more cumulative N₂O emissions (1.05 kg ha^-1) than drained soils (0.79 kg ha^-1), however no significant differences were observed in 2016 (0.73 and 0.63 kg ha^-1 for drained and undrained soils, respectively). Residual N application from the corn phase of the rotation did not affect cumulative N₂O emissions in the soybean growing season in both years. Field-scale N₂O emissions follows the same pattern than cumulative N₂O emissions in both years. The field-scale N₂O emissions measured in this study were comparable to those previously measured under similar conditions in corn receiving no nitrogen, and 3.3 times lower than corn receiving the EONR of 135 kg N ha^-1.