Method and system for automatically detecting nitrogen content, electronic device and medium

A system for automatically detecting nitrogen content, comprising:

• an image acquisition module, which is configured to acquire a spectral image of a target crop;
• a model selecting module, which is configured to select an optimal nitrogen content prediction model from a prediction model base according to a variety and a growth stage of the target crop to obtain a target model;
• a nitrogen content predicting module, which is configured to detect, based on the spectral image of the target crop, a nitrogen content of the target crop by using the target model to obtain a predicted value of the nitrogen content of the target crop;
• a model constructing module, which is configured to construct the prediction model base;
• wherein the model constructing module comprises:
• a sample set acquisition unit, which is configured to acquire a sample set, wherein the sample set comprises:
• spectral images of sample crops of different varieties in different growth stages and true values of nitrogen contents of the sample crops;
• a first model constructing unit, which is configured to extract hyperspectral vegetation indices of the spectral images of the sample crops, and construct a first nitrogen content prediction model according to a correlation between the hyperspectral vegetation indices of different varieties in different growth stages and the true values of the nitrogen contents;
• a second model constructing unit, which is configured to extract sensitive bands of the spectral images of the sample crops, and construct a second nitrogen content prediction model according to a correlation between the sensitive bands of different varieties in different growth stages and the true values of the nitrogen contents;
• wherein the sensitive bands are a characteristic bands whose correlation with the true values of the nitrogen contents is greater than a predetermined correlation value;
• a third model constructing unit, which is configured to train a machine learning model by using the sample set to obtain a third nitrogen content prediction model;
• an optimal model determining unit, which is configured to, for any variety in any growth stage, determine a model with best performance among the first nitrogen content prediction model, the second nitrogen content prediction model and the third nitrogen content prediction model as the optimal nitrogen content prediction model.