CORESTA Meeting, Agronomy/Phytopathology, 2019, Victoria Falls, AP 20

Implications of chloride application rate and nitrogen fertilizer source on flue-cured tobacco

VANN M.C.(1); HARDY D.H.(2); FISHER L.R.(1)
(1) North Carolina State University, Department of Crop & Soil Sciences, Raleigh, NC, U.S.A.; (2) North Carolina Department of Agriculture & Consumer Services - Agronomic Division, Raleigh, NC, U.S.A.

Chloride (Cl-) assimilation by flue-cured tobacco can be toxic and may negatively impact leaf quality and combustion when tissue concentration exceeds 1 %. Uptake is influenced by exposure to NH4+ and Cl-, particularly that coming from fertilizer. The impact of these factors has not been fully described in modern systems utilizing reduced-cost or custom-blend fertility programs. Research was conducted to test the interaction of four Cl- application rates (0, 34, 67, and 101 kg ha-1) and four nitrogen (N) fertilizer sources (calcium nitrate, ammonium nitrate, urea-ammonium nitrate, and ammonium sulfate) on the growth and development of flue-cured tobacco. The impact of N source was minimal in green tissue; however, ammonium sulfate reduced cured leaf quality relative to other N sources. Chloride rates ≥ 34 kg ha-1 reduced foliar total N and NO3 measurements by 0.12 to 0.42 % and 789 to 1,348 mg kg-1, respectively, two weeks after application. Nitrate concentration was also reduced at layby, while P, K, and Mg responded positively to Cl- application between in late-season measurements. After curing, total N and alkaloids were reduced while reducing sugars were maximized as Cl- application increased from 0 to 34 kg ha-1. Chloride concentration exceeded 1 % in application rates ≥ 34 kg ha-1 in early-season and post-curing measurements, although toxic symptoms were not observed nor were yield, quality, or value affected. In order to maintain cured leaf quality producers should utilize N sources containing ≥ 25 % NO3. Likewise, Cl- application should not exceed 34 kg ha-1 in order to maintain the integrity of manufactured products.