Environmental Implications of Polymer Coated Urea

Nitrogen is an essential plant nutrient in the biosphere. Although N is necessary and beneficial for life, it is also a common pollutant in the atmosphere and hydrosphere as it may be lost to the atmosphere as ammonia (NH 3 ) or nitrous oxide (N 2 O) gases or to groundwater as nitrate (NO 3- ) following fertilization. Polymer coated urea (PCU) is one type of N fertilizer which uses temperature-controlled diffusion to control N release to better match plant demand and mitigate environmental losses of N. The objectives of this project were to simultaneously compare the effects of PCU on gaseous (as N 2 O and NH 3 ) and aqueous (as NO 3- ) N losses to the environment as compared to uncoated urea in grass systems over the entire PCU N-release period and to investigate the viability of photoacoustic infrared spectroscopy as a method to ascertain N 2 O and NH 3 losses following fertilization. Two field studies were conducted on established turfgrass sites with a mixture of Kentucky bluegrass (KBG; Poa pratensis L.) and perennial ryegrass (PRG; Lolium perenne L.) in sand (Site 1) and loam (Site 2) soils. Each study compared an untreated control to 200 kg N ha -1 applied as either uncoated urea or PCU (Duration 45 CR®). In these studies PCU reduced NH 3 emissions by 41-49% and N 2 O emissions by 16-54%, while improving growth and verdure. Leachate NO 3- observations were inconclusive at each site. Glasshouse studies were conducted to compare N 2 O and NH 3 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 studies (17-21 d) were done with sand, sandy loam, and loam soils and a full-term (45 d) study with the loam soil. Each study was done in maize ( Zea mays L.). Volatilization of ammonia was reduced by 72% and 22% in the sandy loam and loam soils, respectively, in 2008-2009 and by 14% in the loam in 2010. Evolution of N 2 O was reduced by 42% and 63% in the sandy loam and loam soils in 2008-2009 and by 99% in the loam in 2010. Overall, PCU decreased gaseous losses of N following fertilization while providing a steady supply of N to the plant. The utilization of PAIRS is a viable analysis method which gives higher temporal resolution analysis than is typically reported. These considerable decreases in environmental losses of N are major steps toward conserving natural resources and mitigating the negative environmental impacts associated with N fertilization in grass systems. ABSTRACT Nitrogen is an essential plant nutrient in the biosphere. Although N is necessary and beneficial for life, it is also a common pollutant in the atmosphere and hydrosphere as it may be lost to the atmosphere as ammonia (NH 3 ) or nitrous oxide (N 2 O) gases or to groundwater as nitrate (NO 3- ) following fertilization. Polymer coated urea (PCU) is one type of N fertilizer which uses temperature-controlled diffusion to control N release to better match plant demand and mitigate environmental losses of N. The objectives of this study were to simultaneously compare the effects of PCU on gaseous (as N 2 O and NH 3 ) and aqueous (as NO 3- ) N losses to the environment as compared to traditional uncoated urea in a cool season turfgrass system over the entire PCU N-release period. Two field studies were conducted on established turfgrass sites with a mixture of Kentucky bluegrass ( Poa pratensis L.) and perennial ryegrass ( Lolium perenne L.) in sand (Site 1) and loam (Site 2) soils. Each study compared an untreated control to 200 kg N ha -1 applied as either uncoated urea or PCU (Duration 45 CR®). Using uncoated urea as an N fertilizer resulted in 127 – 476% more measured N 2 O impact on the environment, whereas PCU was only 25 – 52% higher (not significant) than background emission levels. Compared to urea, PCU reduced NH 3 emissions by 41 – 49 % and N 2 O emissions by 45 – 73%, while improving growth and verdure over the control. Leachate NO 3- reductions were inconclusive. These considerable decreases in environmental losses of N are major steps toward conserving natural resources and mitigating the negative environmental impacts associated with N fertilization in turfgrass. ABSTRACT Although N is beneficial and needed for life, it is also a common pollutant in the atmosphere as nitrous oxide (N 2 O) and ammonia (NH 3 )—contributed largely from N fertilization. Polymer-coated urea (PCU) fertilizer is one promising type of controlled release fertilizer that provides improved N-release timing. Glasshouse studies were conducted to compare N 2 O and NH 3 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 studies (17-21 d) were done with sand, sandy loam, and loam soils and a full-term (45 d) study with the loam soil. Volatilization of ammonia was reduced by 72% and 22% in the sandy loam and loam soils, respectively, in 2008-2009 and by 14% in the loam in 2010. Evolution of N 2 O was reduced by 42% and 63% in the sandy loam and loam soils in 2008-2009 and by 99% in the loam in 2010. Overall, PCU decreased gaseous losses of N following fertilization while providing a steady supply of N to the plant. The utilization of PAIRS is a viable analysis method which gives higher temporal resolution analysis than is typically reported.