The prediction model of nitrogen nutrition in cotton canopy leaves based on hyperspectral visible‐near infrared band feature fusion

Hyperspectral remote sensing technology is becoming increasingly popular in various fields due to its ability to provide detailed information about crop growth and nutritional status. The use of hyperspectral technology to predict SPAD (Soil and Plant Analyzer Development) values during cotton growth and adopt precise fertilization management measures is crucial for achieving high yield and fertilizer efficiency. To detect the nitrogen nutrition in cotton canopy leaves quickly, a non‐destructive nitrogen nutrition retrieval model was proposed based on the spectral fusion features of the cotton canopy. The hyperspectral vegetation index and multifractal features were fused to predict the SPAD value and identify the amount of fertilizer applied at different levels. The random decision forest algorithm was used as the model predictor and classifier. A method was introduced which was widely used in the fields of finance and stocks (MF‐DFA) into the field of agriculture to extract fractal features of cotton spectral reflectance. Comparing the fusion feature with multi‐fractal feature and vegetation index, the results showed that the fusion feature parameters had higher accuracy and better stability than using a single feature or feature combination. The R2 was as high as 0.8363, and the RMSE was 1.8767%. Our intelligent model provides a new idea for detecting nitrogen nutrition in cotton canopy leaves rapidly. Graphical and Lay Summary The SPAD value is directly proportional to the nitrogen nutrition of crops. By analyzing the SPAD value, the growth status of plants can be understood, agricultural production management measures can be adjusted in a timely manner, and crop growth and development can be optimized. In this study, a widely used feature extraction method was introduced in finance and stock markets, namely MF‐DFA, to extract multifractal features of cotton canopy spectra, and introduced vegetation index for feature fusion. A hyperspectral feature fusion SPAD value inversion model and a recognition model with different fertilization rates was proposed, achieving excellent model performance. This provides more reference for crop parameter inversion and recognition research.