Fig. 1. Band Selection

Fig. 2. The spectrum, texture and color characteristics of winter wheat image in different periods

Fig. 3. (a) The original image; (b) The wheat under natural gas stress identified by LSSVM; (c) The bare soil; (d): The result of corrosion expansion operation; (e) The extracted stress boundary and the circle fitting boundary of stress region

Fig. 4. Recognition results

Fig. 5. Model Validation

Fig. 6. Green halo phenomenon