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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 Rates and Timing of UAN Application for Winter Wheat, 2000
Comparisons were made among NH4NO3, urea-(NH4)2SO4, and urea-NH4NO3 (UAN) solution at 0, 30, 60, 90, 120, and 150 lb/A of spring-applied N in 1997-98. In 1998-99, a UAN-calcium nitrate [Ca(NO3)2] treatment was added. Treatments were applied on March 1. There was a significant N source by N rate interaction in 1999. Wheat yields increased with N rates up to 120 lb/A (91 bu/A) in 1999, a trend consistent with the 1998 yields. A separate study compared five different application times (from mid-February to mid-April) of NH4NO3 and UAN at 90 lb N/A. The highest yields in 1999 were observed with N applications made between March 1 and 30. Across N timings, NH4NO3 resulted in significantly greater yields compared to UAN: 80 vs. 74 bu/A.
The study was repeated in 1999-2000, but the urea-(NH4)2SO4 treatment was replaced by (NH4)2SO4. Broadcasting NH4NO3 at 90 lb N/A (62 bu/A) or 150 lb N/A as (NH4)2SO4 (59 bu/A) provided the highest yields. Plots were heavily infested with take-all disease in 2000, and yields were lower compared to previous years. Increasing the N rate did not affect wheat test weights in 2000 as it had previously. The test weights were significantly greater with (NH4)2SO4, NH4NO3, and UAN-Ca(NO3)2 compared to urea and UAN sources. These results indicate NH4NO3 tends to provide higher wheat yields at 90 to 120 lb N/A in this part of the Midsouth region compared to the other N sources studied on wheat. TN-14F
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