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ARS Home » Midwest Area » St. Paul, Minnesota » Soil and Water Management Research » Research » Publications at this Location » Publication #237485
Title: Urea Decreases Nitrous Oxide Emissions Compared with Anhydrous Ammonia in a Minnesota Corn Cropping System

Author
item Venterea, Rodney - Rod
item Dolan, Michael
item OCHSNER, TYSON - OKLAHOMA STATE UNIV.

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2009
Publication Date: 3/1/2020
Citation: Venterea, R.T., Dolan, M.S., Ochsner, T.E. 2010. Urea Decreases Nitrous Oxide Emissions Compared with Anhydrous Ammonia in a Minnesota Corn Cropping System. Soil Science Society of America Journal. 74(2):407-418.

Interpretive Summary: Corn and soybean production together account for nearly half of all land used for crops in the U.S. and comprise approximately 8% of total area of the lower 48 states. Anhydrous ammonia and urea are the two most commonly used nitrogen fertilizers in the U.S. Use of these fertilizers can lead to soil-to-atmosphere emissions of nitrous oxide (N2O) gas. N2O is 300 times more potent as a greenhouse gas than carbon dioxide on a pound-for-pound basis. Therefore, measuring soil emissions of N2O associated with production of corn and soybean and using anhydrous ammonia and urea is essential to developing accurate greenhouse gas inventories for agriculture. The objective of this study was to compare N2O emissions in plots managed for more than 15 years under continuous corn cropping versus corn-soybean rotation in fields in southeastern Minnesota. Over three growing seasons, N2O emissions from continuous corn were nearly identical to emissions from the corn-phase of the corn-soybean rotation when either anhydrous ammonia or urea fertilizer was used. However, in both systems, N2O emissions with anhydrous ammonia were twice the emissions with urea. Emissions from the soybean phase of the rotation were lower than the corn-phase. The management-specific estimates of N2O emissions obtained in this study will assist both scientists and policy makers in improving their estimates of greenhouse gas emissions from agriculture, and in developing improved management practices for mitigating these emissions.

Technical Abstract: Quantifying nitrous oxide (N2O) emissions from corn and soybean fields under different management and climate 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 years under continuous corn (C/C) versus corn-soybean (C/S) rotation in southeastern Minnesota. Over three growing seasons, N2O emissions from C/C were nearly identical to C/S during the corn-phase when either anhydrous ammonia (AA) or urea (U) fertilizer was used. However, in both systems, N2O emissions with AA were twice the emissions with U. The results indicate that the increase in N2O emissions resulting from a shift from a C/S rotation to C/C can be substantially minimized by using U instead of AA. With U, average growing season emissions for a C/S rotation were 0.8 kg N ha-1, which increased to 1.1 kg N ha-1 for C/C, a difference of only 25%. With AA, average growing season emissions for a C/S rotation were 1.37 kg N ha-1, which increased by 60% to 2.15 kg N ha-1 for C/C. While soil carbon dioxide emissions were 20% higher under C/C, we found no evidence that crop residue from the prior year affected 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, and found that selection of a calculation method can alter the total N2O emissions estimates by as much as 35%.