通过大田试验设置不同氮肥用量小区，在拔节期前用数码相机拍摄冠层彩色图像，建立数码图像获取信息数据。同时采集植物样品与土壤样品进行分析，分别测定SPAD、植株全氮含量、茎基部硝酸盐浓度、植株体内硝酸还原酶活性4项常规氮素营养诊断指标，分析图像数字化指标如绿光绝对值(G)、绿光标准化值[G/(R+G+B)]、绿光与图像亮度的比值(G/L)、绿光与红光的比值(G/R)与以上4项氮素营养指标的相关性，研究利用数字图像技术进行玉米氮素营养诊断的可行性。

Setting up experimental district of different N fertilizer levels, taking colorful photos using digital camera of hat layer before shooting stage, obtaining information from the digital image. At the same time, collecting the sample of plant and soil, then measuring the SPAD readings, plant content of total N, activity of NR and nitrate concentration of stalk basilar, analyzing the relativity of the digital index of image and the other 4 indexes. The digital index of image include the greenness intensity G, the ratio of greenness and redness intensity G/R, the ratio of greenness intensity and redness intensity G/L and greenness intensity G/(G+R+B). The feasibility could prove the relativity of the indexes that had been discussed.