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基于不同夏玉米品种在2个年份不同施氮水平下的田间试验,研究夏玉米叶片碳氮比随生育期的变化模式及其与冠层反射光谱的定量关系,建立玉米叶片碳氮比的定量监测模型。结果表明,夏玉米叶片碳氮比随施氮量的增加而降低,随生育进程呈“高-低-高”动态变化趋势。利用冠层反射光谱监测叶片碳氮比的适宜时期为孕穗期至吐丝期。13个光谱参数与2个品种叶片碳氮比有较好的相关性。通过比较模型的拟合决定系数(R2)和预测标准误(SE),确定转换型植被指数(TVI)与叶片碳氮比的线性回归方程为最佳监测模型。经不同年际独立试验数据的检验,叶片碳氮比监测模型的预测精确,相关系数(r)为0.682 4,根均方差(RMSE)为0.405 2,表明夏玉米冠层反射光谱可用来定量估测叶片碳氮比的变化状况。
Based on the field experiments of different summer maize varieties under different N application rates in two years, the quantitative relationship between C / N ratio and the canopy reflectance spectra of summer maize leaves was studied. Monitoring model. The results showed that the C / N ratio of summer maize leaves decreased with the increase of nitrogen application rate, and the trend of “high-low-high” was followed with the growth of summer maize. The optimum period for monitoring C / N ratio of canopy by canopy reflectance spectroscopy was from booting stage to silking stage. There was a good correlation between 13 spectral parameters and C / N ratio of two cultivars. By comparing the fitting coefficient (R2) and the prediction standard error (SE) of the model, a linear regression equation of TVI and leaf carbon to nitrogen ratio was selected as the best monitoring model. The results showed that the correlation coefficient (r) was 0.682 4 and root mean square error (RMSE) was 0.405 2, which showed that canopy reflectance spectra of summer maize could be used for quantitative estimation Measurement of leaf carbon / nitrogen ratio changes.