Hyperspectral reflectance characteristics for Spring Wheat in different drought intimidate

Crop is often suffered from drought in semi-arid rainfed agriculture area. Diagnosis of crop drought status is critical for prediction of agriculture drought in this area. Two experiments were conducted for find out spr-wheat canopy spectral characters measurement in different water control status in field in 2007 and 2008, and the experiment included two cultivars and four levels of drought. Hyperspectral canopy and leaf reflectance (350-2500 nm) data recorded at various growth stages and different drought levels were measured by an ASD Field Spec Pro FR2500 in different stages, and the biophysical Parameters were measured at the same time. The hyperspectral reflectance characteristics for Spring Wheat in different drought intimidate at canopy level and the impact of different drought to the biochemical properties of the spring wheat were analyzed. The results revealed following concludes: firstly, the chlorophyll absorb vale change shallow along with the drought level increased, and the reflectance in near infrared region decreased, and the water absorb vale changed shallow at the same time; secondly, the band in 970 nm, 1200 nm, 1650 nm have a highly sensitivity to the drought change, they are the perfect band for the water stress indices design; thirdly, the red edge (Sred)of the spectral is a most sensitivity index for the drought monitoring and the change range From severe drought to no drought is in 718 nm-730 nm. And when the drought increased the red edge shows `blue shift´ phenomena, and the slope of red edge (Dλred) and area of red edge (Sred) of the canopy and leaf spectra are decrease; Fourthly, the leaf water content, leaf area index (LAI) and chlorophyll decreased due to the drought impact, especially, the chlorophyll content, and the spectral change of the spring wheat result in the water content is main by the changing of the chlorophyll.