Nitrogen Nutrition Diagnosis Of Flue-cured Tobacco Based On Ground And Low Altitude Images

Nitrogen plays an important role in the growth and development of flue-cured tobacco.Reasonable application of nitrogen fertilizer can not only increase the yield and quality of tobacco leaves,but also reduce environmental pollution and fertilizer loss caused by nitrogen loss.Therefore,how to quickly monitor the nitrogen nutrition status of flue-cured tobacco and rationally guide field nitrogen management is the key and difficult point in flue-cured tobacco management.This research is based on the nitrogen gradient experiment of flue-cured tobacco in the flue-cured tobacco planting area of Mianning County,Sichuan Province,based on the flue-cured tobacco canopy image obtained by drones,the hyperspectral data of the inverted four leaves obtained by the hyperspectrometer,the SPAD data obtained by the chlorophyll meter,and the mobile phone.Take photos of plant height and canopy images,analyze the response of crop physiology and spectrum indicators to nitrogen,and construct a nitrogen nutrition diagnosis model based on multi-source indicators.This research provides strong scientific support and theoretical basis for deepening the cost reduction and efficiency improvement in flue-cured tobacco production and strengthening the sustainable development of tobacco agriculture.The main conclusions of the full text are as follows:（1）There is a positive correlation between the nitrogen application rate and the yield,and the optimal fertilizer application rate is 124.02 kg/hm² through the fertilizer effect equation.（2）SPAD can better reflect the nitrogen nutrition status of flue-cured tobacco.The best value obtained by this method is the average value of the three parts of leaf tip,leaf middle and leaf base.（3）Plant height and canopy diameter of flue-cured tobacco have the highest correlation with biomass,followed by nitrogen accumulation and nitrogen content.Among the biomass indicators,the comparison of leaf dry weight can reflect the growth of plant height and canopy diameter;among the nitrogen accumulations,the root nitrogen accumulation can best reflect the growth of plant height,and the nitrogen accumulation of the entire single plant can best reflect the canopy diameter Among the nitrogen content indicators,plant height and canopy diameter have the highest correlation with root nitrogen content,and the lowest correlation with leaf nitrogen content.（4）The radiation intensity has the highest correlation with nitrogen accumulation,followed by biomass and nitrogen content.In the nitrogen accumulation index,the root nitrogen accumulation has the largest correlation with the irradiation intensity,the leaf dry weight in the biomass has the largest correlation with the irradiation intensity,and the root nitrogen content in the nitrogen content has the largest correlation with the irradiation intensity;it is related to the above three The sensitive wave band corresponding to high performance is 740-850nm.The fitting equation of irradiation intensity（Re）and nitrogen application rate is Re=-0.6972N²_now+84.259N_now+72756（R²=0.84）,the nitrogen application level is 0-187.5 kg/hm²,and the co rresponding irradiation intensity is 64132.05-75225.95μw/m².（5）The correlation between each index and the nitrogen content and dry matter content is the highest at 50 days after transplanting,and the correlation with nitrogen accumulation is the best at 75days after transplanting.The correlation between vegetation index and nitrogen index is 40 days after transplanting.lowest.From the perspective of the correlation between each index and the vegetation index,NDVI（Normalized Vegetation Index）and OSAVI（Optimization of Soil Regulation Vegetation Index）vegetation index has a good fitting effect with each nitrogen index（r>0.80）;The index correlation is better for the nitrogen content of a single plant;the corresponding parts of the dry matter weight and nitrogen accumulation index with the highest correlation with the vegetation index are the leaves.The fitting equation of NDVI and nitrogen application rate is N_now=1911NDVI-1345.1.