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研究测定了不同施氮水平条件下冬小麦冠层在七个典型生育期叶片叶绿素、地上部分全氮含量以及冠层光谱,分析了单波段反射率、可见光和近红外波段组合而成的归一化植被指数(NDVI)、比值植被指数(RVI)与相应时期叶片叶绿素和地上部分全氮含量的相关性。结果表明,施氮量增加,两个农学参量、冠层近红外波段反射率都随之增加,但当施氮量增加到300kg hm-(2一次性施入)时,上述各项指标均降低;整个生长期中孕穗期在近红外区域反射率最高,与可见光波段反射率相差最大;除分蘖期外,其它时期单波段510nm～1100nm反射率、NDVI、RVI与叶绿素和全氮含量显著相关,植被指数的相关性较单波段高,且从分蘖期到乳熟期,相关性逐渐增强;整体来讲,可见光中560nm、660nm和近红外760nm、1100nm和1200nm组合的NDVI在各生育期与两个农学指标的相关性较好,选择NDVI(560,760)可以准确拟合叶片叶绿素和地上部分全氮含量。
The chlorophyll content, total nitrogen content and canopy spectrum of winter wheat canopy at seven typical growth stages were measured under different nitrogen levels. The normalized reflectance of single wavelength band and the combination of visible and near infrared bands Vegetation Index (NDVI), Ratio of Vegetation Index (RVI) and the correlation between leaf chlorophyll content and aboveground total nitrogen. The results showed that both the agronomic parameters and canopy reflectance increased with the increase of nitrogen application rate, but the above indexes decreased when the nitrogen application rate increased to 300 kg hm-2 During the whole growing period, the booting stage had the highest reflectivity in the near-infrared region and the largest difference with the visible-light region; except for the tillering stage, the NDVI, RVI and chlorophyll- The correlation of vegetation index was higher than that of single band, and the correlation was gradually enhanced from tillering stage to milky maturity stage. Overall, the NDVI of 560nm, 660nm and near infrared 760nm, 1100nm and 1200nm in visible light showed no significant difference The correlation of agronomic indexes is good. Selecting NDVI (560,760) can accurately fit leaf chlorophyll and aboveground total nitrogen content.