Effects of SPAD Value-based Field Nitrogen Management on Yield,Quality and Nitrogen Fertilizer Utilization of Flue-cured Tobacco

In order to solve the problems of insufficient nitrogen fertilizer utilization and deterioration of leaf quality caused by over application of nitrogen fertilizer in tobacco fields,the effects of SPAD value-based real-time nitrogen management(RTNM) mode on the botanical characters,yield,quality and nitrogen fertilizer utilization of flue-cured tobacco were studied in field by using cv.K326 as experimental material.The result showed that in RTNM mode,the application rate of nitrogen fertilizer raised from 60 to 200 kg/ha as the SPAD threshold raised from 38 to 48.Plant height,leaf length,leaf width,and the yield and output values of tobacco leaf increased obviously as the SPAD threshold raised from 38 to 43,and the highest yield and output values were 2844.09 kg/ha and 26989.24 RMB yuan/ha,respectively.Meanwhile,the chemical compositions in tobacco leaf were harmonious and average rate of nitrogen fertilizer utilization reached 46.06%.When SPAD value was over 45.5,the output value,leaf quality and fertilizer utilization decreased significantly.Under the experimental condition,the higher yield,output value and fertilizer utilization of flue-cured tobacco cv.K326 were achievable when SPAD threshold ranged from 40.5 to 43(application rate of nitrogen fertilizer from 75 to 110 kg/ha) in RTNM mode.