Application of SPAD and Vis/NIR Spectroscopy to Estimation Nitrogen Status of Oilseed Rape Plant

The estimation of nitrogen status non-destructively in oilseed rape was performed using spectral reflectance with visible and near infrared reflectance spectroscopy, and SPAD values of the oilseed rape leaves of 30 plots were measured by a SPAD 502 chlorophyll meter, and the research was carried out at experiment field in Zhejiang University during growing season from 2007 to 2008. The SPAD 502 chlorophyll meter was applied to investigate the distribution rule of chlorophyll concentration in the oilseed rape. Regression model between the spectral reflectance and SPAD value was built by partial least squares (PLS). The correlation coefficient (r), root mean square error of prediction (RMSEP) and bias in prediction set were 0.9368, 3.4992 and 1.834e- 07. The correlation between the first derivative of spectral reflectance of oilseed rape leaves and SPAD value were analyzed, and the results showed that good correlation coefficient was obtained in the range from 510 to 640 nm and 685 to 720 nm, and the maximum value for correlation coefficient was at the wavelength 707 nm. The linearity equation between the red edge index and chlorophyll concentration was also analyzed, with the correlation coefficient of 0.986. It is concluded that Vis/NIRS combined SPAD 502 chlorophyll meter was a promising technique to monitor nitrogen status in oilseed rape.