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ARS Home » Midwest Area » St. Paul, Minnesota » Soil and Water Management Research » Research » Publications at this Location » Publication #303163
Title: Anhydrous ammonia injection depth does not affect N2O emissions in a silt loam over two growing seasons

Author
item MAHARJAN, BIJESH - University Of Minnesota
item Venterea, Rodney - Rod

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/2014
Publication Date: 9/15/2014
Publication URL: https://handle.nal.usda.gov/10113/59591
Citation: Maharjan, B., Venterea, R.T. 2014. Anhydrous ammonia injection depth does not affect N2O emissions in a silt loam over two growing seasons. Journal of Environmental Quality. 43(5):1527-1535.

Interpretive Summary: Anhydrous ammonia (AA) is a major source of nitrogen (N) fertilizer in North America and can promote greater emissions of the greenhouse gas nitrous oxide (N2O) than other N fertilizers. Equipment for applying AA at shallower depths has become commercially available, but the effects of shallow versus deep AA application on N2O emissions have been looked at in only two studies having contrasting soil characteristics and also contrasting results. Reduced tillage has been promoted for its benefits, but its effects on N2O emissions have varied widely. We conducted a two-yr field study to compare effects of AA placement depth and contrasting tillage practices on soil N2O emissions in a silt loam soil in Minnesota. In contrast to two previous studies, N2O emissions were not affected by AA placement depth. Usinng the current and previous results, we found a strong correlation (r2=0.989) between soil clay content and AA placement depth effects on N2O such that increasing clay content corresponding to increased N2O with deeper placement. Tillage affected N2O emissions only in the drier of two seasons in which N2O emissions under no-till (NT) exceeded those under conventional tillage (CT) by 55%. Soil moisture content was enhanced to a greater extent under NT in the drier season. These results highlight how management practices interact with soil and climate factors in regulating N2O emissions, and point out that strategies for N2O mitigation need to be evaluated with regard to site-specific factors and their effectiveness has the potential for significant inter-annual variation. These results will be of interest to producers, scientists, non-profit organizations, and government agencies interested in developing effective strategies for reducing the carbon footprint of agricultural production systems.

Technical Abstract: Anhydrous ammonia (AA) is a major fertilizer source in North America and can promote greater emissions of nitrous oxide (N2O) compared to other N fertilizer sources. Equipment for applying AA at shallower depths has become commercially available, but impacts of shallow versus deep AA application on N2O emissions are not well characterized across different soil types. Reduced tillage has been promoted for its benefits but its effects on N2O emissions have varied widely. We conducted a two-yr field study to compare effects of AA placement depth and contrasting tillage practices on soil N2O emissions and crop (Zea mays L.) performance in a silt loam soil in Minnesota. In contrast to two previous studies, N2O emissions were not affected by AA placement depth. Analysis of current and previous results showed a strong correlation (r2=0.989) between soil clay content and AA placement depth effects on N2O, with increasing clay content corresponding to increased N2O with deeper placement. Tillage affected N2O emissions only in the drier of two seasons in which N2O emissions under no-till (NT) exceeded those under conventional tillage (CT) by 55%. Soil moisture content was enhanced to a greater extent under NT in the drier season. These results highlight how management practices interact with soil and climate factors in regulating N2O emissions, and point out that strategies for N2O mitigation need to be evaluated with regard to site-specific factors and their effectiveness has the potential for significant inter-annual variation.