Jeffrey D. Svedin, Brigham Young University, Provo, UT, Bryan G. Hopkins, 701 E. University Parkway, Brigham Young University, Provo, UT and Curtis Ransom, Plant, Insect, and Microbial Sciences, University of Missouri, Columbia, MO
Broadcast topdressing nitrogen fertilizer is a common application method for turf grass. While nitrogen (N) is essential to plant life, broadcast topdressing exposes applied N to potential significant gas loss via ammonia (NH3) volatilization and nitrous oxide (N2O) emission. This gas loss is a financial dilemma which can lead to atmospheric pollution. Polymer coated urea (PCU) and polymer sulfur coated urea (PSCU) are control release fertilizers that engineered to release N over time to match plant demand and have demonstrated reduction of N gas loss. Evaluating N gas loss is regularly done through soil flux measurements, which can be inconsistent due to variability in sampling and escape of N gas. The objectives of this study were to increase precision and accuracy of atmospheric N gas measurement while evaluating the control release properties of PCU and PSCU. A semi enclosed system was created to capture all NH3 volatilization and N2O after fertilizer application. Gas capture and analysis via Photoacoustic Infrared Radar Spectroscopy (PAIRS) was done in a laboratory setting over 48 d. Fertilizer prills were surface applied to a Timpanogos Loam soil. Gases were collected every 1 h. Residual soil N was analyzed at the end of the study. Between 75-89% of the applied N was accounted for throughout the study. The PCU and PSCU both reduced cumulative NH3 volatilization compared to uncoated urea. Polymer coated urea NH3 volatilization was equal to the control during the 48 d period indicating, at these conditions, a near elimination of N gas loss through this fertilizer source. Polymer sulfur coated and PCU both contained over five times less soil NH4-N than uncoated urea and no increase compared to the control, while the PCU NO3-N pool was equal to uncoated urea and PSCU soil NO3-N was greater than uncoated urea. This suggests that when applied uncoated urea floods the soil with NH4-N, whereas PCU and PSCU release N approximately equal to the soil microbial activity. The reduced pool of NH4-N in PCU and PSCU and associated reduction in NH3 volatilization would suggest that the decreased time as NH4-N reduces the applied fertilizer NH3 gas loss. Further research must be done to completely understand control release N fertilizer gas properties within a living turfgrass system which would include plant N intake and variations in temperature, water, and plant and soil interactions.