New Reflectance Spectral Vegetation Indices for Estimating Rice Nitrogen Nutrition III: Development of a New Vegetation Index Based on Canopy Red-Edge Reflectance Spectra to Monitor Rice Canopy Leaf Nitrogen Concentration

摘要

Three field experiments were conducted to study the response of a new vegetation index to nitrogen (N) concentration in rice. The N concentration and hyper spectral canopy reflectance of rice leaves were tested at different growth stages. This was done to select a reflectance spectra wavelength position and to develop better algorithms for estimating N content. We developed the new red-edge reflectance spectra index (RERI), which uses data in three redear-infrared wavebands centered at 681.499, 729.232 and 765.399 nm. Compared to other common spectra vegetation indices (e.g., normalized difference and ratio vegetation indices), our RERI correlated better with chlorophyll and N concentrations, and decreased with decreasing N fertilizer levels. Regression models were built to estimate the N content using RERI. The correlation between measured and predicted N concentrations suggested that RERI sensitively measures the canopy leaf N content.