传统的作物氮营养诊断需要大量的实验室分析和破坏性取样,时效性和便捷性不足。高光谱技术被逐渐应用到作物氮营养监测当中,但由于仪器昂贵并需要专业的软件进行处理,在一定程度上限制了这一技术的应用。文章通过田间试验研究了采用可见光光谱进行夏玉米氮营养诊断的可行性,并试图寻找适宜的表征作物氮营养的可见光光谱参数。研究结果表明,绿光值、蓝光值、红光标准化值、绿光标准化值和蓝光标准化值等多个图像参数均与夏玉米的植株全氮含量、叶片SPAD值有着显著的线性相关关系。在低施氮条件下,叶脉硝酸盐浓度低于2 000 mg·L^-1时,绿光值、蓝光值、绿光标准化值和蓝光标准化值与叶脉硝酸盐浓度有着显著的线性相关关系。而在高施氮条件下,叶脉硝酸盐浓度高于2 000 mg·L^-1时,随着叶脉硝酸盐浓度的升高,图像参数呈平台反应, 不再增加。综合比较来说,以绿光标准化值和蓝光标准化值为最好,与各常规的氮营养诊断指标的相关系数介于0.45-0.66之间。

In the present paper,a field experiment with different N rates was conducted to study the possibility of using the visible spectrum of crop canopy to diagnose N status for the summer maize.Visible spectrum parameters were compared with the leaf SPAD readings,total N concentration and vein nitrate concentration.Field measurement data showed that the greenness intensity,blueness intensity,normalized redness intensity,normalized greenness intensity and normalized blueness intensity of the maize canopy have significant relationships with leaf SPAD readings,total N concentration and vein nitrate concentration (under a low N input condition,with vein nitrate concentration ＜2 000 mg·L^-1) at summer maize 10 leaves unfold stage.The greenness intensity,blueness intensity,normalized greenness intensity and normalized blueness intensity have significant relationship with the vein nitrate concentration under a low N input condition (vein nitrate concentration ＜2 000 mg·L^-1).But when the maize vein nitrate concentration is above 2 000 mg·L^-1,there is no spectral parameter showing significant relationship with the vein nitrate concentration.The visible spectrum parameters reached a plateau with the vein nitrate concentration increasing.To sum up,the normalized greenness intensity (NGI) and normalized blueness intensity (NBI) have higher r values (0.45-0.66) than other parameters.