基于冠层反射光谱的棉花叶片氮含量估测

Estimation of nitrogen concentration in cotton leaf based on canopy reflectance spectra

通过分析不同施氮水平下棉花叶片氮含量与冠层多光谱反射率及其衍生的比值、归一化及差值植被指数之间的关系,确立了棉花叶片氮含量的敏感波段及预测方程.结果表明:由红谷区域(610、660、680和710nm4个波段)和近红外区域(760、810、870、950、1100和1220nm6个波段)组成的植被指数与棉花叶片氮含量的相关性较好,比值植被指数RVI(950,710)对叶片氮含量的预测性最好.利用独立的棉花田间试验资料对基于RVI(950,710)的预测方程进行检验,该模型适用于不同棉花品种及不同生育期棉花叶片氮含量预测.

Through analyzing the relationships of nitrogen concentration in cotton leaf under different nitrogen supply levels with canopy muhi-speetral reflectance and its derived ratio vegetation index （ RVI, Pλ1,/Pλ2 ）, normalized difference vegetation index （ NDVI, （Pλ1, -Pλ2 ） / （Pλ1 ＋ Pλ2 ） ） and differential vegetation index （DVI, P~λ1-Pλ2 ）, the sensitive wave bands and prediction functions of cotton leaf nitrogen concentration were worked out. The vegetation index composed of visible region （610, 660, 680 and 710 nm） and near infrared region （760, 810, 870, 950, 1 100 and 1 220 nm） had a higher correlation with the nitrogen concentration in cotton leaf, and the RVI composed of 950 nm and 710 nm could best predict the leaf nitrogen concentration. The validation with independent field experimental data indicated that RVI （950 nm and 710 nm）-based model was suitable for estimation of leaf nitrogen concentration of different cotton eultivars at their different growth stages.