Optimizing Polymer Coated Urea Applications for Kentucky Bluegrass.

Nitrogen (N) is the most commonly over-applied nutrient in urban environments because of the large visual and measured increases in growth. This over application has led to an increase in the loss of N gas in the forms of ammonia and nitrous oxide, as well as an increase in nitrate leaching to surface and groundwater. Furthermore, excess N results in increased maintenance costs and landfill volume due to increased shoot growth. A two-year study was initiated in April 2014. Seven fertilized treatments were applied to both sand and loam soils in Provo, UT. Treatments included: urea split monthly; a single application of polymer coated urea (PCU; Agrium One Ap) applied in spring, a single PCU application in fall, three evenly split PCU applications in spring, late summer, and late fall; and two evenly split applications in spring and late summer applied at the full rate as well as a 75 and 50% rate. Height and verdure (as measured by NDVI) measurements were taken on a weekly basis, along with periodic visual and biomass readings. As of Fall of 2014, PCU had an average of 21% less shoot height than urea split applied. Verdure, as measured by NDVI and visual scores, was statistically the same for the 75 and 100% rates of PCU compared to urea. Verdure for the 50% rate of N applied as PCU was less than the other treatments. The effect was generally the same for both sand and loam, although the magnitude of the difference was relatively greater for sand. This study continues, but the initial data suggest that the total rate of PCU can be reduced without negative impacts.