Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: June 9, 2011
Publication Date: October 11, 2011
Citation: Phillips, B.L., Ficken, C.D. 2011. Nitrous oxide emissions at the surface of agricultural soils in the Red River Valley of the North, USA. Book Chapter. p. 29-49. IN: (Eds. Guo, L., Guneseka, A. and Hauserman, R.) Understanding Greenhouse Gas Emissions from Agricultural Management. American Chemical Society, Washington, D.C. Interpretive Summary: Nitrous oxide is an important greenhouse gas, as the capacity for nitrous oxide to trap heat is 300 times greater than the capacity for carbon dioxide to trap heat in the atmosphere. Fertilization practices can lead to increased emissions of nitrous oxide at the surface of soils. However, few have tested effects of fertilizer on soil gas emissions using on-farm case studies. This chapter discusses how nitrous oxide is produced and how variable-rate fertilizer application was compared to single-rate fertilizer application using independent farmers located in the Red River Valley of the North, USA. Experiments were designed to evaluate effects of variable, versus single rate application of nitrogen (N). Large fields managed for economic food production were selected, and farm owners continued to manage fields business-as-usual during the study. Effects of fertilizer-N at the agronomic rates applied at St. Thomas, ND and Crookston, MN were not as dramatic as anticipated. There was not a linear relationship between fertilizer rates applied and nitrous oxide emissions, nor was there a linear relationship between fertilizer rates applied and crop yield. Results suggest effects of fertilizer-N on nitrous oxide emissions in situ depend upon soils and the soil environment.
Technical Abstract: Agricultural fertilization worldwide reportedly contributes 6.2 Tg N2O-N yr-1 to a total global source strength of 17.7 Tg N2O-N yr-1, and it is not entirely clear how fertilizer management influences the net flux of N2O from soils. Data are lacking in agriculturally productive areas of the upper Midwestern United States, where sub-zero soil temperatures persist over a prolonged winter. Variable-rate fertilizer management was compared with more conventional, single-rate management to test for differences in N2O emissions using on-farm case studies in the Red River Valley of the North, USA. Varying the amount of N applied did not affect N2O emission rates, and greater amounts of N did not increase crop yields during this 2-year study. Background N2O data measured at undisturbed grass sites suggest N2O emissions at the surface of soils under production agriculture episodically, but not consistently, exceed background.