不同播期冬小麦茎叶碳氮比的光谱监测

为了探讨利用冠层光谱监测不同播期下小麦植株碳氮比的可行性,基于不同播期和不同施氮水平下的两年田间试验,对冬小麦茎叶碳氮比与冠层光谱的关系进行了研究。结果表明,不同播期下冬小麦茎叶碳氮比随生育时期的推进均呈"高-低-高"的动态变化;各个波段综合原始反射率和一阶微分与碳氮比均有显著相关性;NDVI、RDVI、EVI、SAVI等植被指数对茎叶碳氮比均有较好的拟合效果,其中NDVI受播期的影响较小,可用于建立各播期冬小麦茎叶碳氮比监测模型。检验结果显示,冬小麦各播期茎叶碳氮比监测模型的预测精度为0.678 2~0.963 6,相对误差0.095 5~0.323 9,均方根误差1.864 6~5.714 2,说明利用冠层光谱可以实现对不同播期条件下冬小麦茎叶碳氮比较为准确的监测。

Monitoring of C/N Ratio in Stems and Leaves of Winter Wheat Sowed at Different Dates with Canopy Reflectance Spectra

Carbon and nitrogen metabolism as the physiological basis of yield and quality can reflect the physiology status and growth activity of plant. Monitoring of C/N ratio is necessary for growth diagnosis and nitrogen management in wheat production rapidly and non destructively. The research was carried out for 2 years to determine the relationship between C/N ratio measured and canopy spectra under different sowing dates and N levels. The results showed that the C/N ratio in the stems and leaves of wheat revealed a trend of high low high pattern during its growth period, and the canopy reflectance and its first derivative reflectance at certain wavelengths were significantly related with C/N ratio in the stems and leaves of wheat. The C/N ratio in stems and leaves of wheat could be predicted well with the vegetation indexes of NDVI, RDVI, EVI and SAVI, and NDVI could hardly influenced by sowing dates, which could be used as the ideal parameter for predicting C/N ratio in winter wheat under different sowing dates to establish the monitoring model. Tests calibrated with the second experiment showed that the precision of estimated C/N ratio in stems and leaves of wheat was 0.678 2~0.963 6, with the RE of 0.095 5~0.323 9, RMSE of 1.864 6~5.714 2. It suggested that the C/N ratio in stems and leaves of winter wheat under different sowing dates could be accurately estimated based on canopy spectra.