engleski

Comparison of petiole sap nitrate concentration and CCM chlorophyll readings in estimating flue-cured tobacco leaf ripeness at 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 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 mgL-1, 3000 mgL-1 and 2000 mgL-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. The chlorophyll content index (CCI) was measured with a CCM- 200 chlorophyll meter. The nitrate concentration of the 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 a somewhat less significant correlation with the Cardy meter reading in the field and the chlorophyll meter reading, 0.66 and 0.56 respectively. In the evaluation of commercial properties by rapid tests in the field, greater reliability in the assessment of the yield was obtained with the Cardy meter, and in the assessment of the price per kg and value per hectare with the CCM-200 chlorophyll meter.

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

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