Comparsion of Multispectral Reflectance with Digital Color Image in Assessing the Winter Wheat nitrogen Status

Previous researches have shown that the digital image color intensity could reflect the crops N status, but there is little information about the comparision of spectrum reflectance in the visible bands with the digital imagery color intensities. A field experiment was conducted to compare the wheat canopy reflectance at visible bands (400-700 nm) at shooting stage with near ground digital image to detect N deficiencies. Single color bands of R, G, B and ratio indices of G/R, G/B, R/B, R/(R+G+B), G/(R+G+B) and B/(R+G+B), which derived from digital image and spectral measurments, were regressed with wheat N status. The R, G, G/B, R/B, R/(R+G+B) and G/(R+G+B) all had negative correlations, while the G/R and B/(R+G+B) indices had positive correlations, with plant N status. For the B band, the digital image analysis data got positive correlations while the spectral measurements got negative correlations. With higher correlation coefficient than other indices, the R/(R+G+B) was the best index in this research. Considering the easiness of getting digital images and the accurate prediction of crops N status, the digital image analysis method seems to be a better way for in field plant N status evaluation.