Ammonia Volatilization and Effect of Agrotain and SuperU on Winter Wheat Crops in Western Oregon.

Ammonia volatilization represents an agronomic nitrogen (N) loss as well as an environmental pollutant. The use of urea (46-0-0) accounts for approximately 75-85% of the total N fertilizer applied to wheat crops in western Oregon. Little work has been reported on the loss of ammonia in western Oregon where high levels of rainfall occur when N fertilizer is applied to winter wheat crops. Ammonia volatilization was measured with a modified passive flux method at 2 locations; Hillsboro and Corvallis. The N loss as ammonia 24 days after application was 7.20 and 6.00 % of N applied for the above locations, respectively. The Hillsboro location received 13.05 inches of precipitation and the Corvallis location received 15.67 inches of precipitation during the measurement period. A portion of this study, which is still in progress, will measure the effect of two urease inhibitors, Agrotain and SuperU, on grain yield, protein, and test weight on winter wheat crops at both of the study locations. Due to evidence that relatively large amounts of rain received immediately following fertilizer application failed to completely eliminate ammonia losses from urea, further work is warranted to investigate the loss of N from volatilization and determine possible benefits of urease inhibitors in western Oregon crop production.