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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。
The condition of crop nitrogen is an important index to evaluate the growth, increase the yield and improve the quality of crops. It is of great significance to the diagnosis and management of crop nitrogen. Based on the winter wheat canopy spectra and the corresponding leaf nitrogen accumulation data under different nitrogen application levels, the continuous cropping method which is widely used in rock and mine hyperspectral analysis was used to evaluate the crop canopy nitrogen nutrition status. Through the continuum removal of the canopy spectra in the 550-760 nm band, three absorption features were extracted. The results showed that the accumulation of nitrogen in leaves increased with the increase of nitrogen application rate in all growth stages. In all nitrogen treatments, the accumulation of nitrogen in leaves increased from the beginning of growth stage to the jointing stage, booting stage and heading stage Increase and then decrease, and reach the peak at booting stage. In each growth period, the total area of absorption peak, the left area of absorption peak and the right area of absorption peak increase with the increase of nitrogen application rate, and the area is the largest The absorption depth decreased with the increase of nitrogen application rate. Through correlation analysis, it is found that there is a significant correlation between the absorption characteristic parameters and leaf nitrogen accumulation, and the correlation between the normalized maximum absorption depth parameters is the best; the correlation between the whole growth period is higher than that of the single growth period; However, from the perspective of single growth period, booting stage is the best period for monitoring leaf nitrogen accumulation. The results of regression analysis showed that the evaluation model of leaf nitrogen accumulation based on the whole growth period reached the extremely significant level.