Photoacoustic Infrared Spectroscopy to Continuously Measure Nitrous Oxide and Ammonia Emissions From Soil.

Although N is beneficial and essential for life, it is also a common atmospheric pollutant as nitrous oxide (N₂O) and ammonia (NH₃)—contributed largely from N fertilization. Polymer-coated urea (PCU) fertilizer is a promising controlled release fertilizer that provides improved N-release timing. Glasshouse studies were conducted to compare N₂O and NH₃ emissions from PCU and uncoated urea to an untreated control utilizing a non-static, non-flow-through chamber in conjunction with photoacoustic infrared spectroscopy (PAIRS) for gas collection and analysis. Three short-term 20-Day Studies with sand, sandy loam, and loam soils and a full-term 45 Day Study with loam soil were completed. Volatilization of NH₃ was reduced by 72% and 22% in the sandy loam and loam soils, respectively, in two of the short-term studies and by 14% in the loam in the full-term study. Evolution of N₂O was reduced by 42% and 63% in the sandy loam and loam soils of the short-term studies and by 99% in the loam soil of the full-term study. Overall, PCU decreased gaseous losses of N following fertilization while providing a steady supply of N to the plant. Photoacoustic infrared spectroscopy is a viable analysis method that gives higher temporal resolution analysis than is typically reported.