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Title: Nitrogen Source Affects Nitrous Oxide Emissions from Irrigated No-Till Corn in Colorado (USA)

Author
item Halvorson, Ardell
item Del Grosso, Stephen - Steve

Submitted to: Nitrogen Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/23/2008
Publication Date: 6/28/2009
Citation: Halvorson, A.D., Del Grosso, S.J. 2009. Nitrogen Source Affects Nitrous Oxide Emissions from Irrigated No-Till Corn in Colorado (USA). In: Grignani, C., Acutis, M., Zavatto, L., Bechini, L. Betora, C., Gallina, P.M. and Sacco, D. eds.). Proceedings 16th Nitrogen Workshop, Connecting Different Scales of Nitrogen Use in Agriculture. June 28 to July 1, 2009. Turin, Italy. (abstract). p. 161-162.

Interpretive Summary:

Technical Abstract: Introduction Nitrogen fertilization is essential for optimizing corn yields and economic returns in irrigated cropping systems in the USA Central Great Plains area (Maddux and Halvorson, 2008). However, N application generally increases nitrous oxide (N2O) emissions from cropping systems (Mosier et al., 2006; Halvorson et al., 2008, 2009). Agriculture contributes approximately 78% of the total N2O emissions in the USA. An extensive review of greenhouse gas emissions from cropping systems (Snyder et al. 2007), showed little information available on N fertilization effects on N2O emissions from irrigated cropping systems in western U.S.A., and in particular the effects of commercially available controlled-release and stabilized N sources on N2O emissions. The global warming potential of N2O is approximately 296 times greater than that of CO2, thus it is important to develop methods to reduce N2O emissions in agricultural systems. Our objective was to evaluate the effect of N source on N2O emissions from an irrigated, no-till (NT) continuous corn (CC) field in northern Colorado, USA (40o 39’ N; 104o 59’ W; 1535 m a.s.l.). Materials and Methods Nitrous oxide emissions from plots receiving dry granular urea (46% N) and liquid urea-ammonium nitrate (UAN; 32% N) were compared with those receiving controlled release and stabilized N sources at rates of 0 and 246 kg N/ha in 2007 and 0 and 202 kg N/ha in 2008. Controlled release, polymer-coated urea sources were ESN® (44% N) and Duration III® (43% N) produced by Agrium Advanced Technologies, Sylacauga, AL. Stabilized N sources were SuperU® (46% N) which is a granulated urea impregnated with a urease and nitrification inhibitor, and UAN treated with AgrotainPlus® (UAN+AP). The SuperU® and AgrotainPlus®, produced by Agrotain International, St. Louis, MO, contain urease (N-(n-butyl)-thiophosphoric triamide) and nitrification (dicyandiamide) inhibitors. The N was band applied in the corn row at emergence with 1.3 cm of sprinkler-irrigation water applied within 3 days. The soil, a Fort Collins clay loam (fine-loamy, mixed, superactive, mesic Aridic Haplustalfs), has a SOM content of about 2.1%; pH of 7.6; and clay and sand content of 33 and 40%, respectively. A randomized complete block design with 3 replications was used. Nitrous oxide fluxes were measured during the growing season at two locations within each plot using static, vented chambers, 1 to 3 times per week, and a gas chromatograph analyzer (Mosier et al., 2006). Total 2007 yearly precipitation was 273 mm with a May - October corn growing season total of 201 mm. The 2008 yearly precipitation totaled 296 mm, with a May - October corn growing season total of 241 mm. A tornado passed through the plot area on 22 May 2008 accompanied by 11 mm rainfall and damaging hail. Again on 14 August, a hail storm damaged the corn crop severely, with >50% (estimated) leaf defoliation accompanied by 3 days of rainfall totaling 98 mm. Irrigation water applied totaled 406 mm in 2007 and 360 mm in 2008. Results Growing season N2O emissions were similar both years for each N source. The two year average, growing-season cumulative N2O fluxes are shown in the Fig. 1 below for each of the N sources. Dry granular urea had the greatest growing season N2O emission followed by UAN, Duration III®, and ESN® with the SuperU® and UAN+AP treatments having the lowest N2O emissions. When compared to urea, the controlled release (ESN®) and stabilized N (SuperU®) sources reduced N2O emissions 33 and 48%, respectively, in this irrigated NT continuous corn production system. Addition of AgrotainPlus® to the UAN solution reduced N2O emissions 35% when compared to UAN alone. Application of SuperU® resulted in a 29% reduction in N2O emissions compared with UAN alone. The check (no N applied) treatment had the lowest level of N2O emissions during the