Effects of Harvesting Time on Economic Characters and Quality of Flue-cured Tobacco Under Different Fertilization Application Regimes

In order to study the suitable harvest time of tobacco leaf under different fertilization application regimes, NC55 culivar was used and three fertilization application regimes were set up as follows:all nitrogenous, phosphorous and potassic fertilizers were used as basal fertilizer (T1); phosphorous fertilizer for basal application in total, nitrogenous fertilizer and potassic fertilizer were applied with a base and topdressing ratio of 7:3 (T2); phosphorous fertilizer for basal application in total, nitrogenous fertilizer and potassic fertilizer were applied with a base and topdressing ratio of 5:5 (T3). The three harvest time treatments were as follows:30 days after topping (S1), 35 days after topping (S2) and 40 days after topping (S3). The leaf SPAD value, economic characters, chemical composition, and quality of tobacco after curing were analyzed. The results indicated that for the same regime of fertilization application, the leaf SPAD value decreased with the extension of harvest time after topping.The proportion of high-quality tobacco, high and middle-quality tobacco after curing, the average price and the single leaf weight all increased firstly and then decreased and all of them had the highest value at 35 days after topping. There was smaller differencesof the proportion of high and middle-quality tobacco, the average price and single leaf weight for the T3 regime between treatment of 35 and 40 days after topping. With the extension of harvest time, leaf nicotine content significantly decreased, reducing sugar content, reducing sugar/nicotine, and reducing sugar/total sugar significantly increased, the total sugar content firstly increased and then decreased, and showed the highest at 35 days after topping. At different fertilization application regimes, the reduction of leaf SPAD value decreased following higher ratio of nitrogenous and potassic fertilizers topdressing. When the base and topdressing ratio of nitrogenous and potassic fertilizers were 10:0, 7:3 and 5:5 respectively, the harvest time for the highest sensory quality of flue-cured tobacco were 30 days, 35 days and 40 days after topping, respectively. It can be concluded that the increasing the top dressing ratio of nitrogenous and potassic fertilizers with total basal application of phosphorous fertilizer delayed the harvest time to get the best quality.