Effects of Different Nitrogen Fertilizer Raters on Growth and Chemical Quality of Tobacco with Drip Irrigation under Plastic Mulch

A field experiment with drip irrigation under plastic mulch was conducted to study effects of three nitrogen fertilizer rates(high nitrogen content of 97.5 kg/hm2;moderate nitrogen content of 82.5 kg/hm2;low nitrogen content of 67.5 kg/hm2) on growth of tobacco plant,activity of nitrate reductase in tobacco leaf and coordination of chemical components in flue-cured tobacco leaf.The results showed that plant height and leaf number of tobacco in vigorous growth period and bud stage increased with increasing nitrogen fertilizer rate;the treatment with high nitrogen content significantly increased stem width,length of middle-part leaf and number of leaves remained per plant(P0.05);the nitrogen fertilizer rate had no significant influence on width of middle-part leaf;increasing nitrogen fertilizer rate can improve activity of nitrate reductase in tobacco leaf in early growth period(45 d after transplanting);in treatment with moderate nitrogen content,the ratio of sugar to alkali and the ratio of nitrogen to alkali in flue-cured tobacco leaf were appropriate,the contents of soluble sugar,reducing sugar,starch and total nitrogen were moderate in middle-upper leaves,otherwise,the protein content was the lowest and the nicotine content was the highest.Therefore,when adopting technology of drip irrigation under plastic mulch,the nitrogen fertilizer rate of 82.5 kg/hm2 was appropriate for growth of tobacco plant,moreover,the chemical quality and coordination of chemical components in flue-cured tobacco leaves were relatively better.