Burley tobacco (Nicotiana tabacumL.) has historically been fertilized with nitrogen rates ranging from 150 to 250 kg N/ha. The objectives of the this study were to: (i) evaluate the response of burley tobacco to N fertilization; (ii) determine if split N applications increase burley tobacco yields; and (iii) evaluate a modified pre‐sidedress soil nitrate test (PSNT) as a tool for N management in burley tobacco. Nitrogen rates included: 0, 67, 135, 202, and 270 kg N/ha preplant in combination with 0 and 67 kg/ha N sidedress. In 2008, the 270 kg N/ha rate was dropped and the variety TN 90LC was added to the study. Modified pre‐sidedress nitrate test (PSNT) samples were taken to a depth of 15 cm prior to sidedress N applications. Analysis of variance was used to analyze burley tobacco yield response to preplant and sidedress N applications and polynomial regression was used to analyze PSNT levels and preplant N rates. Optimal yields were reached with 135 kg N/ha. Pre‐sidedress nitrate test levels in 2008 predicted yields more precisely than in 2007 due to higher precipitation at experimental sites. The information from the study indicates that burley tobacco yields were maintained at lower N rates than traditional N applications rates.
Phytophthora-induced plant diseases are most effectively managed using an integrated strategy that includes host resistance, best cultural practices, and fungicide applications. Black shank, caused by Phytophthora nicotianae, is the most significant soilborne disease affecting tobacco, and extensive breeding for resistance has resulted in an array of varieties with a spectrum of black shank resistance. Estimates of plant survival are the most common measurement in tobacco black shank trials, however, survival may not be the most accurate indicator of yield for varieties with robust resistance. Through the presented analyses, at-harvest green yield estimates are shown to be more closely associated with cured tobacco yields than survival counts, irrespective of black shank resistance status. However, green yield may only be considered a standalone yield predictor for low resistance varieties, with other factors likely contributing to cured yield of moderate and high resistance varieties. This prevents development of a unified (variety-nonspecific) cured yield model, which would be useful not only for tobacco scientists, but also commercial growers in planning labor activities and the industry at-large in managing cured tobacco inventory. More broadly, this suggests that research in other Phytophthora pathosystems may benefit from yield estimates in addition to survival counts in resistant variety evaluations.
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