Effect of Agrotain, Ammonium Sulfate, and Urea on Ammonia Volatilization Loss and Rice Grain Yield When Applied at Different Times Prior to Flooding

The preflood nitrogen (N) fertilizer sets the yield potential of the rice cultivars being grown and thus, its management is critical to obtaining profitable rice grain yields. The objectives of this study were to evaluate the ammonia volatilization loss and impact on rice yield when urea, Agrotain®, and ammonium sulfate were applied preflood and a flood established at 1, 5, and 10 days after N application. Fifteen to 20% of the urea-N, only 3 to 5% of the ammonium sulfate-N, and only 2 to 3% of the Agrotain-N was lost via ammonia volatilization within 5 days of application. By 10 days after application and time of flooding, the losses from ammonia volatilization where leveling off at about 17 to 25% for the urea, 4 to 10% for the Agrotain, and 3 to 5% for the ammonium sulfate. When flooding was delayed for 5 and 10 days after N fertilizer application, Agrotain and ammonium sulfate produced the highest grain yields which were quite similar and were significantly higher than those produced with urea. Rice grain yields did not decline or declined only slightly as N fertilizer application time before flooding increased to 5 and 10 days when Agrotain or ammonium sulfate were applied. If more than 2 to 3 days is required to move the floodwater completely across a rice field after the preflood N fertilizer has been applied then a N fertilizer such as Agrotain or ammonium sulfate should be used. AAES Research Series 517