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Interpretive Summaries:
2003 - Influence of Nitrogen Fertilizer Source, Application Rate and Timing on Grain Yields of Delayed- Flood Rice
2002 - Influence of Nitrogen Fertilizer Source, Application Rate, and Timing on Grain Yields of Rice
2001 - Influence of Nitrogen Fertilizer Source, Application Rate, and Timing on Grain Yields of Rice
2000 - Influence of Nitrogen Application Rate, Time, and Source on Rice Yields
1999 - Influence of Nitrogen Application Rate, Time and Source on Rice Yields
Influence of Nitrogen Fertilizer Source, Application Rate, and Timing on Grain Yields of Delayed-Flood Rice, 2003
Drill-seeded rice (Wells variety) yield and ammonia volatilization response to urea, ammonium sulfate (AS), and a 50:50 mixture of urea and AS were evaluated with and without Agrotain®, on a silt loam soil with 7.6 pH . The nitrogen (N) was applied pre-flood and compared under 1, 5, and 10 day delayed-flood management after surface broadcast application of the N. The N rates were 0, 60, and 120 lb/A for yield comparisons. Ammonia loss (volatilization) of the different N sources was evaluated using the 120 lb rate applied 10 days prior to flooding. Within 5 days of application, urea lost almost 15% of the applied N while the AS and Agrotain® lost only about 3% and 1%. By 10 days after application and the time of flooding, the ammonia losses of the applied N had leveled off at about 17% for the urea and about 4% for the Agrotain®, respectively. Ammonia volatilization losses of N from AS with flooding delayed until 10 days after N application were not significantly different from those measured at 5, 15, or 20 days after application. Rice grain yields reflected the pattern of N loss with the different sources, rates, and delayed flooding. Agrotain®, AS, and AS + Agrotain® had the highest grain yields and least ammonia volatilized when application was made 5 and 10 days prior to flooding. Rice grain yields were intermediate when AS + urea was applied at 5 and 10 days before flooding. Ammonium sulfate + urea also had intermediate ammonia volatilization losses at these times compared to the other N sources. Most of the yield decrease measured when the flood was delayed from 5 to 10 days was probably due to nitrification of the N sources and denitrification after flooding. AR-18F
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