不同生育期冬小麦光谱特征对叶绿素和氮素的响应研究

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。

Response of Winter Wheat Spectral Reflectance to Leaf Chlorophyll,Total Nitrogen of Above Ground

Field experiments were conducted at seven typical growth stages of winter wheat,to measure the leaf chlorophyll,total nitrogen of above ground and canopy spectral reflectance in different N status,to analyze the correlation between the single wavebands,NDVI/RVI of combined visible light and near infrared and chlorophyll,or total nitrogen concentration.The results showed that leaf chlorophyll,total nitrogen of above ground and canopy spectral reflectance in near infrared increased with the increasing nitrogen rate until 300kg ha-1(applied one-off).There were remarkable correlation between single wavebands from 560nm to 1100nm,NDVI,RVI and two agronomic parameters except at tillering growth stage.The correlation coefficient of vegetation index were higher than single wavebands reflectance and increased from tillering to filling growth stage,gradually.On the whole,the ability of NDVI/RVI of 560nm and 660nm in visible light and 760nm,1100nm,and 1200nm in near infrared were better than others.NDVI(560,760) could estimate the content of leaf chlorophyl1and above ground total nitrogen accuracy.These results indicated that canopy spectral reflectance could be used to non-destructively monitor of leaf of chlorophyll and N status in winter wheat.