Effect of Nutrisphere on Ammonia Volatilization Loss of Urea and the Grain Yield of Drill-Seeded, Delayed Flood Rice.

Field studies were conducted in Arkansas and Mississippi to determine if Nutrisphere treated urea could be applied up to 10 days prior to flooding with minimal loss of rice grain yield. Grain yield was measured in three field studies with delayed flood rice where urea was treated with and without Nutrisphere applied up to 10 days prior to flooding. A laboratory, incubation study measured the ammonia volatilization of urea, Nutrisphere treated urea, Agrotain treated urea, and ammonium sulfate applied to soil over a 15 day period. Although there was a significant influence of nitrogen (N) rate and application timing on rice grain yield, there was no significant influence from Nutrisphere. Rice grain yield significantly decreased as the time between N fertilizer application and flooding was increased from 1 to 10 days whether the urea was treated or not treated with Nutrisphere. This finding brought into question Nutrisphere's urease inhibition claims and the initiation of a laboratory, incubation study. In the incubation study ammonium sulfate had the least amount of ammonia volatilized followed by Agrotain treated urea. Urea and Nutrisphere treated urea had the most ammonia volatilized. Nutrisphere did not significantly inhibit ammonia volatilization of urea and is thus, not an effective urease inhibitor.