Quantitative remote sensing in crop biochemical parameters inversion and stripe rust monitoring

Remote sensing offers the potential to determine rapidly the physiological condition of crop over large areas. Spectral reflectance measurements at leaf and canopy scales in the field provide a promising, quick and nondestructive way to take information in relatively wide area in a short time. Canopy reflectance data selected at key growth stages of winter wheat were analyzed. It indicated that winter wheat growth phonological changes can be evaluated by Red Edge Variables (REV) characteristics. Regression equations between foliar chlorophyll concentration, nitrogen concentration, soluble sugar etc. and REV were established, prediction of foliar soluble sugar and chlorophyll concentration by red edge position, foliar nitrogen concentration by the amplitude of red edge, starch concentration by the near infrared plateau, leaf area index by the area of red edge peak are successful feasible. Wheat yellow rust is also called as stripe rust, it caused the primary yield loss of China's wheat production industry. The traditional method of field survey for wheat yellow rust disease indices (DI) is time consuming. This study was to develop the appropriate spectral indices from in situ reflected spectrum and hyperspectral images for extraction DI of yellow rust and use this information to predict the onset of this disease in wheat in a timely and less labor intensive manner. When wheat was infected by yellow rust, The Photochemical Reflectance Index (PRD was chosen for DI inversion. There is linear negative relation between the normalized photochemical reflectance index (NPRD extracted from in situ canopy reflected spectrum and DI with a coefficient of determination R-2 = 0. 9417 (n = 87) by the data in 2002, and the DI value between investigated and simulated data in 2003 with a coefficient of determination R-2 = 0. 9477 (n= 117), so the Normalized Photochemical Reflectance Index (NPRD can be used to inverse DI. This paper also suggested the possibility of developing a special visible sensor for detecting DI of wheat yellow rust theoretically.