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Interpretive Summaries:
2000 - Evaluation of Nitrogen Sources and Rates and Timing of UAN Application for Winter Wheat
1999 - Evaluation of Nitrogen Sources, Rates and Timing of UAN Application on Wheat
1998 - Evaluation of Nitrogen Sources and Application Timing for Wheat
Evaluation of Nitrogen Sources and Application Timing for Wheat, 1998
Research was initiated in the fall of 1997 to compare ammonium nitrate (AN), urea (U), urea plus ammonium sulfate (UAS), and urea-ammonium nitrate (UAN) solution at 0, 30, 60, 90, 120 and 150 lb/A of spring-applied N. The UAN was applied with flat fan nozzles from a CO2 pressurized sprayer and the other N sources were applied with a 12-foot Gandy drop-type spreader. Yield, disease severity, flag leaf N concentration, N uptake, grain moisture, and test weight were measured. Yields increased incrementally with N rates up to a maximum of 63.4 bu/A with 120 lb/A of spring-applied N. Across N rates, AN yielded the most (58.6 bu/A) while the other N sources did not differ (55.5 to 56.4 bu/A). There was a significant rate by source effect on yield, grain moisture, test weight, flag leaf N concentration, and plant N uptake. A separate study compared application timing of AN and UAN at 90 lb/A of spring-applied N. Five different application times were evaluated. The first N application was made in mid-February and the other four times were spaced at two week intervals thereafter. Application timing did not affect yields. Ammonium nitrate produced higher yields than the UAN treatment (57.1 vs. 52.2 bu/A). These early results indicate that N sources for wheat may differ in effectiveness in this part of the Midsouth region. TN-14F
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