基于连续统去除法的冬小麦叶片氮积累量的高光谱评价

Hyperspectral evaluation of nitrogen accumulation in winter wheat leaves based on continuum-removed method

作物氮素状况是评价长势、提高产量和改善品质的重要指标,它对作物氮素诊断与管理具有重要意义。本文基于不同施氮水平下的冬小麦冠层光谱及相应的叶片氮积累量数据,将广泛应用于岩矿高光谱分析中的连续统去除法借用至作物冠层氮素营养状况评价。通过对550-760nm波段的冠层光谱进行连续统去除处理,提取了3个吸收特征。结果表明：在所有生育期中,叶片氮积累量均随着施氮量的增加而增大;在所有氮处理中,从起身期、拔节期、孕穗期到抽穗期,叶片氮积累量均呈先增加后减小的趋势,且在孕穗期达到峰值;在各生育期,吸收峰总面积、吸收峰左面积和吸收峰右面积均随着施氮量的增加而增大,面积归一化最大吸收深度均随着施氮量的增加而减小。通过相关分析发现：各吸收特征参数与叶片氮积累量之间均存在显著性相关,且面积归一化最大吸收深度参数的相关性最好;全生育期的相关性高于各单生育期;但从单生育期来看,孕穗期是监测叶片氮积累量最佳时期。回归分析结果发现,基于全生育期建立的叶片氮积累量评价模型均达到了极显著性水平。

Crop nitrogen status is a key indicator of crop growth, yield production, and grain quality, and of significance in crop nitrogen diagnosis and management. Based on the data of winter wheat canopy spectra and corresponding leaf nitrogen accumulation （LNA） acquired under different nitrogen application levels, the nitrogen nutrition of crop canopy was evaluated by continuum-removed method, a widely used method in spectra analysis of rock and mineral. Three absorption features were acquired by the continuum-removed treatment of canopy spectra ranging from 550 nm to 760 nm. The LNA at all growth stages increased with increasing nitrogen fertilization; but under the same levels of nitrogen application, the LNA increased from erecting stage to booting stage, and decreased from booting stage to heading stage. At all growth stages, the total area of absorption peak （TA） , left area of absorption peak （LA） , and right area of absorption peak （RA） increased with increasing nitrogen fertilization, whereas the normalized maximal absorption depth by area （NMAD） decreased. All the absorption feature parameters of continuumremoved spectra had significant correlations with LNA, and the relationship between NMAD and LNA was the best. The correlations in whole growth period were higher than that at any growth stage. From the viewpoint of growth stage, booting stage was the best growth stage to monitor the LNA. Regression analysis displayed that the LNA regression model based on the whole growth period was most available.