不同形式的光谱参量对春玉米氮素营养诊断的比较

Nitrogen nutrition diagnosis for corn using different spectral parameters

选择适宜的光谱参量,对利用光谱技术进行作物营养诊断精确度的提高是至关重要的。该文对单因素氮处理下春玉米(ZeamayL.)不同层位叶片光谱反射率与氮含量作了相关分析,探讨了叶片水平上单波段光谱反射率(R)、单波段光谱反射率的对数(LgR)、双波段组合光谱反射率(R1+R2)、以及对数形式的双波段组合光谱反射率(LgR1+LgR2)4种形式光谱参量对氮素营养诊断的可靠性。结果表明,第6片完全展开叶叶片光谱反射率与氮含量在可见光波段存在较高的负相关关系,以550和720nm两波段组合的光谱参量(LgR550+LgR720和Lg(R550+R720))建立的线性回归方程的拟合度最好;不同生育期应选择对养分盈亏敏感的叶片作为营养诊断的光谱监测目标,不同生育期叶片氮素营养的光谱敏感波段不同,应选择二者相关性高的波段,较为适宜的光谱参量形式与营养成分建立估算模型。研究表明,经对数处理后的光谱参量,无论是单波段还是双波段,拟合方程的精度都有不同程度的提高,且方程的稳定性也增强,说明对数形式的光谱参量提高了对氮素营养诊断的精确度。

In the field of crop nutrition diagnosis by spectrum technology,it is greatly important that selecting right spectrum parameters to improve accuracy and precision.The objectives of this experiment were to identify wavelengths and/or their combinations that are indicative of nitrogen nutritional condition and to analyze the accuracy of different forms spectral parameters for nitrogen nutrition diagnosis.Corn（Zea may L.）different layer leaf reflectance spectra and nitrogen content of different nitrogen treatments were measured at key development stages.Correlation analysis between spectral reflectance of different layer leaf and nitrogen content were made and linear regression equations were constructed between spectral parameters and nitrogen content.The accuracy of nitrogen nutrition diagnosis among the single wave-band spectral reflectance（R）,the logarithm of single wave-band spectral reflectance（LgR）,the dual wave-bands spectral reflectance（R1＋R2）,and the logarithm of dual wave-bands spectral reflectance（LgR1＋LgR2）were compared.The results showed that the high negative correlativity between the 6th expanded leaf spectral reflectance and nitrogen content was existed in visible spectrum region.The fittings of the linear regression equation constructed by spectra variables（LgR550＋LgR720,Lg（R550＋R720））and nitrogen content respectively were best among them.Sensitive leaves to nutrient profit and loss should be chosen to be regarded as nutrition diagnosis objects of spectral detection in different stages.Spectral sensitive bands to nitrogen nutrition varied with development stages,so more bands of high correlation and more reliable spectral parameters should be selected to construct models with nutrient elements.The results showed that after the logarithm treatment on spectral parameters,whatever either single band or dual bands,the precision of the regression equation was improved and its stability was strengthened.Its observations suggest that it is great potential that using spectral parameters to make nutritional diagnosis for crops,and more suitable spectral parameters or vegetation index for nutritional diagnosis should be investigated and selected.So more research still need to be conducted to test and improve crop nitrogen diagnosis model.