Trace Gas Fluxes, Global Warming Potential and Greenhouse Gas Intensity Related to Tillage and Nitrogen Application with and without Nitrapyrin in Rainfed Corn.

On-farm studies were conducted in Indiana over a 3-yr period to assess effect of tillage and nitrogen (N) fertilizer application, with and without nitrapyrin (Instinct^®), on seasonal carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) fluxes, global warming potential (GWP) and greenhouse gas intensity (GHGI) during corn production.  Tillage consisted of no-till (NT) and conventional tillage (CT) or reduced tillage (RT), and N was applied as UAN at a single N rate, with and without nitrapyrin (Instinct^®).  Seasonal CO₂, CH₄, and N₂O were measured weekly for up to 8 weeks, and thereafter biweekly during the growing season, and corn yield recorded at harvest.  Global warming potential due to treatment was estimated by multiplying cumulative CO₂, CH₄ and N₂O by appropriate factors as recommended by the Inter-governmental Panel on Climate Change (IPCC) and summing across all GHGs, and GHGI was estimated by dividing GWP by yield.  Tillage and N source effects on GHG fluxes varied significantly by year and location.  The soil acted as a minor sink of CH₄ across treatments or locations. No-till and RT/CT, respectively, resulted in 2055 and 2068 kg CO₂ ha^-1, and in 780 and 910 kg CO₂-eq ha^-1 of N₂O emissions.  Without Instinct, UAN resulted in 2274 kg CO₂ and 748 kg CO₂-eq yr^-1 of N₂O, while UAN+Instinct resulted in 2111 kg CO₂ and 539 kg CO₂-eq yr^-1 N₂O emissions. Global warming potential ranged from 2135 to 4015 kg CO₂-eq for UAN, but was 1903-3320 kg CO₂-eq for UAN+Instinct.  GHGI for UAN was 0.31 kg CO₂-eq kg⁻¹ grain and was 14% greater than for UAN+Instinct, and 9% greater for NT relative to CT or RT (0.32 kg CO2-eq kg⁻¹ grain).  Our results indicated that UAN+Instinct has the potential to reduce global warming under NT or CT/RT.