库尔勒香梨叶片全钾含量高光谱估算模型研究

为实现库尔勒香梨养分状况的无损、实时、快速监测,利用便携式光谱仪(SVC HR-768)测定不同钾肥施用量的20年树龄库尔勒香梨叶片光谱反射率,并结合叶片全钾含量的室内分析,对叶片全钾含量与原始光谱、一阶导数光谱、高光谱参数之间相关性进行分析。结果表明:在425 nm处原始光谱与叶片全钾含量构建的线性模型,调整决定系数R2值达到0.913;在630 nm处一阶微分光谱与全钾含量构建的线性模型,调整决定系数R2值为0.986。叶片全钾含量与高光谱特征变量中绿峰位置变量(Rg)和红谷位置变量(Ro)的相关性极显著,由此构建的线性模型调整决定系数R2值均达到0.96以上。通过模型检验,确定基于630 nm的光谱一阶微分(X630)模型Y=1 136.835X630+50.709为库尔勒香梨叶片全钾含量(Y)的最优估测模型。

Hyperspectral estimation models for total potassium content of Kuerle fragrant pear leaves

The conventional analysis of nutrient elements required destructive sampling, highly complex processes, highly time consuming and difficult nutrition diagnosis process in fruit trees. However, hyperspectral remote sensing technology has been reported to resolve the problems of destructive sampling and rapidly diagnose nutrient elements of plant. To monitor the state of nutrients in Korla fragrant pear in a non-destructive, timely and quick manner, an SVC HR-768 portable spectrometer was used to measure the spectral reflectance of leaves in the field of 20-year Korla fragrant pear tree under different K fertilization rates. The total K content was analyzed in the lab, and the relationships between total K content of leaves and original spectrum, first derivative spectrum, high spectral parameters established. The results showed that a single linear model built at 425 nm between total potassium content and original spectrum significantly described the relationship, with an adjusted determination coefficient (R²) of 0.913. Another linear model built at 630 nm between total potassium content and the first order derivative spectrum was similarly significant, with an adjusted R² of 0.986. The relationships bewteen total potassium content of leaf and green peak position (Rg), red valley position (Ro) were extremely significant in selecting hyperspectral feature variables. Results also showed that the adjusted R² was above 0.96 for all the built linear models. After evaluation of all the built models, the model Y = 1 136.835X₆₃₀ + 50.709 (X₆₃₀ is the first derivative spectrum at 630 nm) was the best for predicting total potassium content (Y) of Korla fragrant pear leaf.