Variation rules of the nitrogen content of the oilseed rape at growth stage using SPAD and visible-NIR

In order to obtain the variation rules of the nitrogen content of oilseed rape at its growth stages, and to guide suitable fertilization, the completely expanding leaves in the third branch counted from the top branch were tracked and analyzed by SAPD meters. The result shows that interim of the bud to anthesis was the best period for nitrogen fertilizer management. Spectral properties of the oilseed rape leaves were also measured using visible-near infrared reflectance spectrometer(Visible-NIR) with natural illumination. Multiple linear stepwise regression technique was used to analyze the relationships between SPAD values and the reflectance spectra. The result shows that single linear regression model with the first derivative reflectance spectra in 683 nm can accurately predict SPAD values. The correlation coefficient of the predicted samples was 0.801.