Abstract
In recent years, many studies have been reported on remote sensing techniques in agricultural production to utilize the advantage of simultaneous and wider monitoring capability of satellite data. Several studies have been conducted to develop links between spectral reflectance and temperature for traditional paddy rice cultivation. In our study to characterize the spectral reflectance of paddy rice (Oryza sativa L., cv. Hinohikari) with the lengthening growing days, the spectral reflectance of rice leaves from 400 nm to 1, 100 nm wavelength range was acquired with a handheld spectroradiometer. A wide range of nitrogen (N) was applied in experimentally field-grown paddy rice. To develop a growth model for paddy rice we analyzed physical parameters, spectral reflectance and fractional photosynthetically active radiation (fPAR). The following conclusions were drawn: (1) Different spectral characteristics were observed during the growth stages for different N-treatments; (2) Detection of significant differences between N-treatments was realized with the ratio vegetation index (RVI) at full heading stage; (3) Red edge points poorly correlated with leaf area index (LAI), dry weight (DW) and fPAR; (4) The R830/R550 ratio highly correlated with LAI and DW during the entire growing season. The prediction accuracy of fPAR was also very high using the R830/R550 ratio. Though our study accounts for only limited factors, it was concluded that growth models for monitoring paddy rice could be based on RVI and the R830/R550 ratio.
