ARS | Publication request: Urea Fertilizer Decreases N2O Emissions Compared to Anhydrous Ammonia in Corn Cropping Systems in Minnesota

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 2009
Publication Date: November 1, 2009
Citation: Venterea, R.T., Dolan, M.S., Ochsner, T.E. 2009. Urea Fertilizer Decreases N2O Emissions Compared to Anhydrous Ammonia in Corn Cropping Systems in Minnesota [abstract]. ASA-CSSA-SSSA Annual Meeting Abstracts. Paper No. 37.

Technical Abstract: Quantifying nitrous oxide (N2O) emissions from corn and soybean fields under different fertilizer regimes is essential to developing national inventories of greenhouse gas (GHG) emissions. The objective of this study was to compare N2O emissions in plots managed for more than 15 yr under continuous corn (C/C) versus corn-soybean (C/S) rotation that were fertilized during the corn-phase with either anhydrous ammonia (AA) or urea (U). Over three growing seasons, N2O emissions from C/C were nearly identical to C/S. However, in both systems, N2O emissions with AA were twice the emissions with U. After accounting for N2O emissions during the soybean-phase, it was estimated that a shift from C/S to C/C would result in an increase in emissions of 0.78 kg N ha-1 (equivalent to 0.11 Mg CO2-C ha-1) when AA was used, compared to an increase of only 0.21 kg N ha-1 (0.03 Mg CO2-C ha-1) when U was used as fertilizer. In light of global trends toward increased use of U, these results have the positive implication that fertilizer-induced N2O emissions may decline in future, at least per unit of applied N. While soil carbon dioxide emissions were 20% higher under C/C, crop residue from the prior year did not affect soil inorganic N or dissolved organic carbon (DOC) levels during the subsequent season, although DOC levels with AA were higher than with U. We also compared different flux-calculation schemes, including a new method for correcting chamber-induced errors, and found that selection of a calculation method altered seasonal emissions estimates by as much as 35%.