[Spectral Characteristics Analysis of Wheat Damaged by Subsurface Waterlogging]

Spectrum analysis of crop that affected by subsurface waterlogging is the foundation of surface waterlogging monitoring by remote sensing in large scale. It is also the prerequisite of achieving non-destructive, quick identification of wheat subsurface waterlogging damage with spectral features. But there is no papers report about spectrum analysis of crop affected by subsurface waterlogging so far. The paper analysis the spectral features difference of 8 species (zenmai9023, xinong223, luo6010, fumai168, emai23, emai19, guangyuang11-2, nongda195) between affected subsurface waterlogging and normal in leaf and canopy model using field experiment. The results shows that the leaf spectrum reflectivity value of wheat affected by subsurface waterlogging is high in 645～680 and 1 428～1 456 while it is lower in 757～917 and 1 641～1 684 nm. The main reason is that the subsurface waterlogging causes the leaf chlorophyll photosynthetic capacity decreased and leaf water loss. It is suggested to use NDWI (normal differential water index) value to indicate the damage degree of wheat subsurface waterlogging disaster. The changes of the NDWI index value is analyzed with time when difference wheat species demerged by subsurface waterlogging. It is found that the main factors caused the changes of the NDWI index value with time is related with resistance of variety. The canopy spectrum reflectivity value of wheat affected by subsurface waterlogging is low in all spectrum area. It is suggested to use average value in 670～240 nm to indicate the degree of wheat subsurface waterlogging disaster.