engleski

Response and method of harvest of flue-cured tobacco as estimated by petiole sap nitrate test

Tobacco ripening was studied during 2006 and 2007. The treatments in the field trials were topping height (twenty and seventeen leaves for harvest), method of harvest (seven, four and three primings), and ripeness (4000 mgL-1, 3000 mgL-1 and < 2000 mgL-1 of nitrate). The ripeness was estimated using petiole sap nitrate test (Lyons and all., 1996), thus tobacco was harvested at 4000 mgL-1, 3000 mgL-1 and < 2000 mgL-1 of nitrate in lower 10 cm of the main leaf midrib. The year 2006 was more favorable for tobacco production, especially according to the amount of rainfall from July to September (317.0 mm), than year 2007 (166.2 mm). Number of harvests had little effect on the agronomic traits. Only in 2007 four harvests resulted in significantly higher yield than harvests in three or seven primings. In 2006, year with more rain, harvesting tobacco when the leaf midrib had the lowest content of nitrate (< 2000 mgL-1) resulted in the lowest price and value. However in 2007, less rainy year, with decreasing nitrate content in the midrib, yield, price and value increased. In both years total N and protein content in the leaf decreased with the decreased nitrate content. In 2006 reducing sugars also decreased with the decreased content of midrib nitrates. In 2006 climatically more favorable year for tobacco production, significant topping x ripeness interaction for total nitrogen content, protein N and reduced sugars was found. In 2007 significant topping x ripeness interaction was found for the nicotine content. The results observed in this study have shown that the content of nitrate in the bottom 10 cm of leaf midrib could be reliable indicator of leaf ripeness for harvesting

sap nitrate; harvest method; ripeness; flue-cured tobacco

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