Assessing The Efficacy Of Nitrification and Urease Inhibitors On Nitrous Oxide and Ammonia Emissions In Forage Seed Production In The Saskatchewan Parkland Region.

Forage seed production requires significant fertility inputs, and differs from forage feed production in that fertilizer strategies focus on seed rather than biomass production. Because forages grasses are perennial and are typically grown for three or more years, N fertilizer cannot be incorporated into the soil and is instead broadcast on the surface. Urea, which is the most commonly used form of N fertilizer in the Parkland region, is subject to a variety of losses—including ammonia (NH₃) volatilization and denitrification-induced nitrous oxide (N₂O) emission. These losses may negatively impact the nitrogen use efficiency (NUE) of the fertilizer N; consequently, producers are looking for strategies that reduce N losses from broadcast applications of N fertilizer. One possible strategy involves the use of urease and nitrification inhibitors.

The aim of this study was to assess the use of urease and nitrification inhibitors in forage seed production to reduce gaseous N losses to the environment and increase NUE. Sites were established in existing forage seed fields at four locations in the Parkland region of Saskatchewan to evaluate the impact of fall and spring applications of urea and three stabilized urea fertilizers on NH₃ volatilization and N₂O emissions. The fertilizers were urea treated with Agrotain^® (a urease inhibitor) and the stabilized fertilizers Alzon^® (urea + a nitrification inhibitor) and SuperU^® (urea  + urease and nitrification  inhibitors). Fertilizers were applied in the fall of 2012 and the spring of 2013 at a rate of 92 kg N ha^-1. Immediately after fertilizer application in fall, NH₃ volatilization was measured consecutively every day until snowfall occurred, and again after snowmelt the following spring. After spring application of fertilizers, NH₃ volatilization was measured daily for three weeks. Nitrous oxide emissions were measured twice to thrice per week in the fall of 2012 and in the spring of 2013. Ammonia  emissions were measured by connecting forced-drought chambers (chambers through which an air flow is guided) to acid traps (sulfuric acid), followed by colorimetric analysis of the trap solutions. Nitrous oxide emissions were measured by collecting gas samples from non-steady state, vented chambers and analyzing the samples using gas chromatography.