See more from this Session: Agriculture, Emissions, and Air Quality
Tuesday, October 18, 2011: 8:35 AM
Henry Gonzalez Convention Center, Room 210A, Concourse Level
Nitrous oxide (N2O) is a potent soil-derived greenhouse gas that significantly contributes to global warming; N2O comprise 40-44% of the CO2 equivalent emissions from soil under rain-fed, and 16-33% under irrigated corn in the United States. On a global scale, agricultural N2O emissions are projected to increase 35-60% by 2030 due to increased N fertilizer use and animal manure production (FAO, 2003). We reviewed research conducted in the last 3 decades to determine the current state of knowledge on the effects of nitrification inhibitors and related aspects of N management on the rate of nitrification of applied nitrogen fertilizers, N2O emissions from soil, and nitrogen use efficiency (NUE) in corn. Although scientists agree that most nitrification inhibitors delay the nitrification process, and have potential to reduce N2O emissions from fertilized cornfields, opinion is divided whether these delays significantly lowered growing-season N2O emissions, improved NUE and/or corn yield. Nitrapyrin, the most commonly used nitrification inhibitor, occasionally reduced corn yield at agronomic optimum N application rates, even though significant yield increases due to nitrapyrin were observed at lower-than-optimum N fertilizer rates. Few experiments have been conducted to address how timing of N application and placement depths (with or without inhibitors), and spread across the various N application timeframes used by corn farmers (e.g. early fall, late fall/pre-plant and spring pre-plant or sidedress applications) affect N2O emissions. In particular, limited data exist to assess N2O emissions following spring sidedress-applied N, especially given the availability of reformulated nitrapyrin - Instinct™ - for application with liquid N fertilizers, and the introduction of more N efficient corn hybrids in use today. On-going experiments across Indiana indicate that Instinct™ reduced N2O emissions by up to 53%, across soil and tillage systems. Availability of technologies that can integrate nitrification inhibitors and N management options in time and space offers opportunity for further research in integrated nitrification inhibitors and N management that best reduce N2O emissions in corn.