Abstract
In order to assess the grain protein concentration of winter wheat before maturing stage, we proposed a new vegetation index of rbNDVI (red and blue Normalized Difference Vegetation Index) for the estimation of leaf chlorophyll concentration at heading to anthesis stage. rbNDVI derived from the hyperspectral measurements of red (630nm) and blue (445nm) showed the highest correlation with leaf chlorophyll concentration (r2=0.701 for 2006, 0.802 for 2007) comparing with the widely used NDVI (Normalized Difference Vegetation Index) and TCARI/OSAVI (Transformed Chlorophyll Absorption in Reflectance Index/Optimized Soil-Adjusted Vegetation Index). Moreover, difference of equations between 2006 and 2007 was also smallest in rbNDVI (RMSE: Root Mean Square Error=4.77µg cm-2）. In addition, simulation trial with ALOS/AVNIR-2 (Advanced Land Observing Satellite/Advanced Visible and Near Infrared Radiometer type 2) broadband (blue: 420-500nm, and red: 610-690nm), compared with narrowband (445nm and 630nm), obtained by spectral measurement resulted almost same accuracy level. It highlights the feasibility of satellite monitoring of leaf chlorophyll concentration using the newly developed rbNDVI in the earlier growth stage of wheat. Information by rbNDVI may suggest effective manuring practice for the current year to enhance grain protein concentration through nitrogen application of wheat at heading to anthesis stage.
