采用Field-Spec Pro便携式光谱仪, 测定了不同苹果品种叶片的光谱反射率及对应的全氮含量, 采用相关性及单变量线性与非线性拟合分析技术, 对全氮含量与原始光谱反射率、一阶微分光谱、高光谱参数之间的关系进行了分析。研究确立叶片全氮含量的定量监测模型, 以期为遥感技术在苹果氮素营养诊断中的实际应用提供理论依据。结果表明: 全氮含量与原始光谱在715nm 处具有最大负相关系数(r = ?0. 817), 并且基于此波长所构建的对数关系估算模型明显优于线性模型; 光谱反射率一阶微分值在723nm 处具有最大正相关系数(r = 0.87), 并且基于此波长所构建的线性和非线性模型的拟合效果接近; 对于所选取的3类高光谱特征变量, 全氮含量除了与黄边位置及由红边位置和黄边面积所构建的比值植被指数和归一化植被指数的相关性较弱外, 与其余变量均呈极显著相关, 说明这些变量对苹果叶片全氮含量进行估算具有可行性。对所建立的各类方程进行检验, 最终筛选确定在723nm 处的光谱反射率一阶微分值所构建的指数模型作为苹果叶片全氮含量的预测模型最为理想。

Plant nitrogen status is a key indicator for evaluating crop growth, increasing yield and improving grain quality. Non-destructive and rapid assessment of leaf nitrogen is required for improving nitrogen management in fruit tree production. The hyperspectral reflectance and corresponding total nitrogen concentration of different species of apple trees’ leaves were measured by Field-Spec PMI-MASTER PRO. The correlation among raw hyperspectral reflectance, first derivative spectra, and hyperspectral characteristic variables were analyzed. This paper makes a model for the quantitative detection of leaf ’s total nitrogen with a view to providing a theoretical foundation for nutrition diagnosis of the apple by remote technology. The results showed that the raw spectral reflectance has the maximum negative correlation coefficient at 715nm (r = ?0.817) with total nitrogen concentration and the logarithm model constructed with reflectance at this point is the better one as compared to linear model; the first derivative spectral reflectance has the maximum positive correlation coefficient at 723nm (r = 0.87) and the linear and non-linear models have the similar capacity for the nit rogen est imation; as to hyperspectral characteristic variables, they all show significant correlation with nitrogen contents except λy, SD /SDy and (SDr + SDy)/(SDr ? SDy). Those results indicate that the variables adopt in this paper have great potential for nitrogen concentration test. By the precision evaluation of estima-tion models, the logarithm model constructed by the first derivative reflectance at 723 nm was proved to be the best for the esti-mation of apple leaves nitrogen concentration.