Image analysis method in application of digital image on diagnosing wheat nitrogen status

Easy, fast and cheap diagnosis of crop nitrogen status is a key to optimize nitrogen fertilization. Crop nitrogen status can be measured by relating it to color parameters retrieved form digital images. In this paper, color parameters of digital image of winter wheat under different levels of nitrogen supply were analyzed by using Adobe Photoshop and PCI Geomatics remote sensing image processing software and the results compared. Based on color differences, winter wheat image was divided into three parts (soil, leaves with and without reflection). Correlations among eight color parameters retrieved by PCI and Photoshop, SPAD values and total nitrogen content of wheat were analyzed. The results showed that G/R and R/(R+G+B) ratios of leaves with reflection were significantly correlated with wheat SPAD at reviving stage. R/(R+G+B) ratio of leaves with and without reflection was significantly correlated with wheat total nitrogen content at jointing stage. It was noted that improvements in image processing for getting color parameters of software were required. Color parameters obtained via image classification could increase the diagnosis accuracy of wheat nitrogen status.