Ammonia Volatilization from Foliar-applied Urea on Field-grown Kentucky Bluegrass

Abstract

Ammonia (NH 3 ) volatilization was determined from 15 N-labeled urea applied foliarly in 35 ml·m −2 water at 1.7 and 3.4 g N/m 2 to a ’Park’ Kentucky bluegrass ( Poa pratensis L.) turf that was grown on Sharpsburg silty clay loam (Typic Argiudoll). Field measurements of NH 3 volatilization were made 1, 5, 9, 13, and 25 hr after treatment (HAT). Additional volatilization measurements were made at 2, 3, and 4 days after treatment (DAT). Maximum NH 3 losses of 9.7 and 23.0 mg N/m 2 per hr at 5 and 25 HAT occurred with the 3.4 g N/m 2 treatment. Maximum volatilization during 25 HAT coincided with periods of high leaf surface moisture followed by rapid drying. On the second day after treatment, the maximum NH 3 loss of 14.0 mg N/m 2 per hr occurred from the 3.4 g N/m 2 treatment. Cumulative 4-day NH 3 volatilization losses for foliar-applied urea at 1.7 and 3.4 g N/m 2 were 35% and 31%.