The effect of irrigation scheduling and water stress on the maturity and chemical composition of Virginia tobacco leaf

Abstract

The study was carried out in order to determine the effect of different irrigation scheduling programs and water stress, imposed at different growth stages, on the maturity and leaf chemistry of Virginia tobacco ( Nicotiana tabacum L.). Field experiments and lab investigations were carried out during 2000–2003, on a silty loam Entisol soil, poor in organic matter and rich in potassium, on the fields of Atatürk Soil and Water Resources Research Institute in Kirklareli, Turkey. A randomized complete block experimental design with three replications was applied, and K-326 Virginia tobacco cultivar was used in the experiment. Three known stages of the plant – vegetative (V), yield formation (F), and ripening (R) – were considered, and a total of 14 irrigation treatments (including rain-fed) were applied. All the experimental treatments were irrigated on the same day of VFR and were irrigated at each growth stage with the amount of water required to fill the 0–90 cm soil depth to field capacity; and three levels of water reductions (0%, 40% and 60%) were done at each development stage. Results of the investigations show that irrigation scheduling and the water stress imposed during different stages of growth influenced the ripening dynamics of Virginia tobacco leaves and that severe water stress causes delay in the ripening of the leaves. Favorable moisture conditions considerably decrease the nicotine and nitrogen content of the Virginia tobacco leaves, both of which are hazardous for humans, to the ranges of 0.85–1.21% versus 2.1–2.2% under stress (for nicotine), and 1.4–1.6% versus 1.8–2.0%, and 2.0–2.4% versus 2.9–3.1% (for nitrogen) for 2001 and 2003, respectively. However the percentage of chloride and sodium in the leaf increases if the amount of seasonal water is increased. It was determined also that close linear relationships exist between seasonal irrigation water amounts or seasonal evapotranspiration and any of the chemical traits. Mutual relationships between nicotine and each of the traits – i.e. nitrogen, chloride, potassium, and sodium – were also established.