engleski

Comparison of petiole nitrate concentrations and CCM chlorophyll readings in estimating ripeness of flue-cured tobacco leaves for harvest

A field trial was conducted for the purpose of comparing two diagnostic tests, the petiole sap nitrate test and the chlorophyll meter, and their applications in determining the ripeness of tobacco leaves for harvest. The experiment was carried out during the 2007 and 2008. The treatments were topping height (20 and 17 leaves for harvest), the manner of harvest (7, 4 and 3 primings) and the degree of ripeness at the time of harvest (4000 mg L-1, 3000 mgL-1 and 2000 mg L-1). The nitrate content was measured in the midrib sap in the laboratory using an ion selective electrode (ISE) and Cardy meter, and in the field using a Cardy meter. Additionally, the chlorophyll content index (CCI) was measured with a CCM-200 chlorophyll meter during the vegetation and at the moment of harvest. The nitrate concentration of the leaf midrib measured with an ISE in the laboratory showed significant correlation with the nitrate concentration measured by the Cardy meter in the laboratory, r=0.95, and there was less significant correlation with the chlorophyll meter reading, r=0.56. However, a stronger correlation, r=0.66, was obtained by comparing the nitrate concentration values measured with the Cardy meter in laboratory and chlorophyll readings in field. The results of these investigations showed that the relationship between nitrate concentrations and chlorophyll readings at the moment of harvest and yield, price per kg and value per ha, could be described by linear equations. The results also showed that a more reliable and significant relationship, especially for price per kg and value per ha, could be achieved with the chlorophyll readings.

nitrate petiole test; Chlorophyll meter; ripeness; flue-cured tobacco

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