Effects Of Nitrogen Application Rate And Planting Density On Growth And Quality Of Flue-cured Tobacco K326

Flue-cured tobacco K326 has showed good agronomic and economic traits in the production since introduced from America into China, and the internal quality is also popular among the tobacco companies. Chongqing is the 8th flue-cured tobacco production areas of China but the flue-cured tobacco varieties is fewer. “Yunyan87” “Yunyan97” are the leading varieties.Because of the technical restriction of ecosystem, cultivation, disease and baking techniques,The enthusiasm of planting K326 is poor for tobacco farmers and the planting area of K326 is small.Its production can’t be supply for the tobacco companies. The reason is due to its production and value.Its intrinsic quality also needs to be further improved. Cultivation measure is one of the most important factor in the process of flue-cured tobacco production and the formation of quality.In order to provide oretical and technical support for the cultivation techniques of K326 in Chongqing, field experiments were conducted to study the nitrogen application rate and planting density and their manner on growth and quality of flue-cured tobacco K326. The main results are as follows:1.The agronomic characters of flue-cured tobacco K326 were mainly affected by the rate of nitrogen application. Plant height, stem circumference, pitch and maximum leaf width were increased with the increase of nitrogen application rate. However, the planting density was mainly affected the stem circumference and productive leaves in Vigorous Growing Period which showed that the stem circumference and productive leaves of tobacco plant were smaller Under the condition of low density, It turned out just the opposite in high density condition. So the suitably increasing of nitrogen application rate and planting density was contribute to the growth of tobacco plant.2. Dry matter accumulation of K326 was influenced by two factors of nitrogen application rate and planting density.Increasing the amount of nitrogen fertilizer could promote the dry matter accumulation of stem and leaf. However, increasing the planting density could reduce the dry matter accumulation and contribute to the dry matter transfer from stem to leaf.3.The activity of nitrate reductase increased obviously with the nitrogen rate’s improvement, it firstly increased and then decreased through the growth period and the highest rate was in vigorous growing period. Then the activity of nitrate reductase reduced and maintained a stable state. The activity of nitrate reductase reduced slowly at the nitrogen application rate 112.5 kg/hm2,it still keeped a high level through the mature period this would put off the carbon fixation and conversion of metabolism transform to the accumulation of carbon metabolism. The quality of tobacco leaf would also decreased. The planting density had no significant influence on the activity of nitrate reductase.The activity of amylase firstly increased and then decreased with the nitrogen rate’s improvement through the growth period but the effect of planting density on amylase activity was related to the amount of nitrogen application. At low nitrogen application rate, the increase of planting density could reduce the amylase activity, however the increasing of the plant density could increase the amylase activity at the condition of high nitrogen application rate. According to the coordination of the carbon-nitrogen metabolism,the appropriate rate of nitrogen applied and planting density were 97.5 kg and 16500-18000 strains per hectare.4. At the early and middle stages of the growth and development, the content of chlorophyll in tobacco leaf firstly increased and then decreased with the improvement of nitrogen rate and planting density. The suitably increasing of nitrogen application rate and planting density could promote the content of chlorophyll in tobacco leaf in photosynthetic stage and then promote the photosynthesis. However,,the content of chlorophyll in tobacco leaf increased with the nitrogen rate’s improvement and decreased with the Planting Density’s improvement in the mature period. It was due to excessive nitrogen application rate result in the tobacco leaf mature later. As a result, the quality of leave would reduce. the suitably increasing of planting density could ameliorate this phenomenon.The content of carotenoid decreased after the vigorous growing period. The nitrogen application rate and planting density had no significant influence on it. The content of carotenoid is too low at the nitrogen application rate 112.5kg/ hm2,this maybe bad for the formation of aroma substance in mature period. According to the tobacco plastid pigment, the appropriate rate of nitrogen and planting density were 105 kg and 18000 strains per hectare.5. The nitrogen application rate had significant influence on nitrogen content, nicotine content,sugar alkali and NIT/NIC. Nitrogen and nicotine content increased obviously with the improvement of nitrogen application rate, on the contrary,sugar alkali decreased obviously with the improvement of nitrogen application rate.The NIT/NIC was lower than other treatments at the nitrogen application rate 112.5kg/ hm2.Increasing the nitrogen application rate contributed to improve the quality of tobacco leaves. But part of treatments had a excessive nicotine content which would result the strong irritation and bad tasty quality at the nitrogen application rate 112.5kg/ hm2.The planting density had significant influence on nitrogen content, sugar alkali, NIT/NIC. Nitrogen content and sugar alkali firstly increased and then decreased with the improvement of planting density rate. While NIT/NIC increased obviously with the improvement of planting density. Nicotine content increased with the planting density.According to the chemical composition contentand their coordination, the appropriate rate of nitrogen applied and planting density were 105 kg and 18000 strains per hectare.6. Increasing the nitrogen application rate was helpful to improve the neutral aroma content in tobacco leaves.of K326.Though the planting density had no significant effect on the content of aroma substances, but the neutral aroma components of flue cured tobacco with medium density were better.