Effects of agronomic measures on economic indexes of flue-cured tobacco variety NC71 introduced from the United States

Through the field experiment, effects of nitrogen rates, leave numbers, topping time and harvesting method for remaining leaves on economic indexes of flue-cured tobacco variety NC71 introduced from the U.S. were investigated. Plant grew faster, leaf area index increased and upper leaf exposed fully both of NC71, when nitrogen application rate increased. These evidences of K326 were more significant than that of NC71. No significantly interactive effect existed between variety and nitrogen rates in main economic traits. The highest total class grade percentage and middle class grade percentage, and leaf commercial value of NC71 were found in the N application treatment of 105 kg/hm2. Middle cured leaf yield was observed in the treatment of 20 leaves per plant whereas it has the highest leaf commercial value because of the highest class grade percentage and grade index. Relatively middle leaf area index, top 6 leaves and cured leaf yield were found in the treatment of topping conducted 5 days later after flower-bud appearing, however, the leaf commercial value was the highest due to higher middle class grade percentage and grade index. CS2(the first two fly leaves were discarded) increased cured leaf yield, grade index and leaf commercial value. It was suggested that the agronomic measures for NC71 under middle soil quality condition were as follows: N application rate was about 105.0 kg/hm2 as the control variety(K326), topping was conducted 5 days later after flower-bud appearing with 20 leaves per plant, and the first two fly leaves were discarded.