Research on nitrogen nutrition diagnosis and precision fertilizing model for flue-cured tobacco

Application of nitrogen (N) fertilizer in tobacco production is well known to increased yield. However, low fertilizer-nitrogen use efficiency (FNUE) and inferior quality of cured-tobacco leaves is a serious problem in tobacco production in China. According to this problem, taking variety K326 as study object, field experiments were conducted in production area of Shaoguan, Guangdong province from 2008 to 2010. Different N levels were designed to study the relation between SPAD value with chlorophyll contents, the change characteristics of N contents and their influences on yield and quality at different leaf orders and different detecting position. The effects of different SPAD values on yield and quality and FNUE of flue-cured tobacco were analyzed by the SPAD-based N-treatment. The results showed that, the third fully-expanded leaf from the top was more suitable for SPAD detection, which could obtain good relativity of SPAD with chlorophyll content and N content. The greater yield and quality of flue-cured tobacco were gained with SPAD value from 38.3 to 47.2 at root extending stage and fast growing stage. In the SPAS-based N-treatment, the high yield and output value of flue-cured tobacco could be achieved when the SPAD threshold was designed within 40.5-43 (N rate was 75-110 kg/hm2), and were 2?844.09 kg/hm2 and 26989.24 yuan/hm2 respectively. Moreover, compared to the conventional application of fertilizer by farmer, the fertilizer-N agronomic efficiency and recovery efficiency were increased by 53.0% and 46.5% respectively, and the output value increased by 7.4% when SPAD value was 43 in the SPAS-based N-treatment (N rate was 110 kg/hm2). The starch, total nitrogen, tobacco nicotine contents in flue-cured tobacco leaves were decreased significantly. When compared to the conventional application of fertilizer by farmer, the chemical components and intrinsic quality in flue-cured tobacco were also improved under real-time nitrogen management.