Effects of Nitrogen Fertilizer on Tobacco Soil Enzyme Activities and Flue-cured Tobacco Immanent Quality

The field experiment was conducted on planting tobacco soil to research variation rules of soil enzyme activities in different soil layers at different stages and to research the effects of different nitrogen levels on tobacco quality.The results showed that at 0-20 cm soil depth,the N application was helpful to increase the activities of soil urease,invertase.When the N applied was over 52.5 kg hm-2,the activities of soil urease,invertase were decreased.The activities of soil protease reached its maximum when the N applied was 37.5 kg hm-2,along with the N of going up,the activities of soil protease presented a trend of decreasing.At 20-80 cm soil depth,the variation laws of the activities of soil urease,invertase,protease were inconsistent.To the flue-cured tobacco,when the N applied was at 52.5 kg hm-2,the ratio of total sugar to nicotine,total nitrogen to nicotine and potassium to chlorine were more appropriate,the chemical composition tended to coordinate and burning performance was much better,and it had still helped to form excellent quality of flue-cured tobacco.It also indicated that 52.5 kg N per hectare was the most proper nitrogen in the paddy soil under the experimental condition.