Masters Theses

Date of Award

5-2007

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant Sciences

Major Professor

H. P. Denton

Committee Members

Robert D. Miller, Hubert J. Savoy

Abstract

Our objectives in this study were to evaluate the state recommendations for nitrogen, determine the effects of nitrogen on tobacco specific nitrosamines (TSNA), yield and quality, determine efficient nitrogen rates and evaluate the pre sidedress nitrate test (PSNT) as an indicator of nitrogen needs in burley tobacco. This study had nine nitrogen rates, in a split plot design with four replications. Main plots consisted of preplant nitrogen: 89.6, 179.2 and 268.8 kg/ha. Sub plots consisted of sidedress nitrogen: 0, 52 and 112 kg/ha. Soil nitrate-N was determined using the PSNT, with samples taken to a depth of 0.15 m three weeks after transplanting. There were two locations in 2004, at Greeneville, TN (GR) and Glade Spring, VA (GL). Two more locations were added in 2005 and 2006, Springfield, TN (HR) and Lexington, KY (LE) along with a tobacco after tobacco (TAT) rotational study at GR and HR also in 2006.

Nitrogen rates within the state recommendations gave yields statistically equal to the maximum. In several cases, yield was maximized by lower than recommended rates. The study showed an increase in yield with an increase in nitrogen above the lowest treatment. All yields, except for HR 2005, exceeded the long term, Tennessee state burley yield average. A positive yield response to sidedress nitrogen fertilizer was observed at the 89.6 kg/ha treatment, with 56 and 112 kg/ha sidedressed and the 179.2 kg/ha treatment with 56 kg/ha sidedressed. There was only one instance with 268.8 kg/ha pre plant nitrogen where there was a positive yield response, likely due to variability within the study. Total TSNA content was also increased with higher nitrogen rates. TSNA content was lower in the dryer 2005 curing season. Although not an objective of this study, and not proven, it is likely that the locations of the curing structures had some effect on TSNA content. PSNT values increased as nitrogen rates increased. From this study the PSNT does not seem to be a precise enough indicator of nitrogen needs in burley tobacco to be used in making N application decisions.

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