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Effects of Method of Harvest on Flue-Cured Tobacco Part II. Chemical Components¹

Tobacco (Nicotiana tabacum L.) is subject to modification of chemical characteristics by alteration of production practices. If a suitable product can be provided for the tobacco manufacturers, utilizing the once-over harvest approach, a much simpler and relatively less expensive harvesting machine could be developed and production costs could be markedly reduced.

Normal and once-over methods of harvesting flue-cured tobacco were evaluated for effects on the chemical characteristics of cured leaves. All plants were topped to 12, 16, or 20 leaves per plant. Stalk position data were compared within the three topping heights.

Lesser percentages of total N and total N-soluble and a lower pH were evident in leaves grown in 1968 than those produced in 1969. As topping height was increased from 12 to 20 leaves per plant, percentages of total N, total N-soluble, nicotine, and water-soluble acids in the leaves decreased, while reducing sugars increased. These chemical changes were attributed to utilization of equivalent amounts of nitrogen for the development of greater number of leaves. Higher concentrations of total N, total N-soluble, nicotine, and water-soluble acids were recorded for leaves harvested by the normal method than when all leaves were removed in one harvest. Undoubtedly, overmature bottom leaves and immature top leaves, associated with the once-over method, influenced the average chemical composition for the whole plant.

The nitrogenous constituents and water soluble acids increasel in leaves from bottom to top stalk positions except for percent alpha amino nitrogen. The pH of leaves decreased from bottom to top stalk positions. Overmature bottom and immature top leaves from the once-over harvest contributed to difference in chemical composition of leaves at the upper and the lower stalk positions. When all leaves were harvested at one time, only bottom and top leaves appeared to be different in chemical composition from those presently being used by the tobacco trades.

Key Words: Normal harvest • Once-over harvest • Stalk position • Topping height • Total N • Insoluble N • Total N-soluble • Alpha amino N • Nicotine • Reducing sugars • Water-soluble acids • pH

² Research Associate and Assistant Professor of Agronomy, respectively.

Received for publication May 26, 1972.