Effects of nitrogen status on leaf anatomy, chlorophyll content and canopy reflectance of paddy rice

摘要

Precision agriculture can reduce the environmental pollution that results from over application of nitrogen (N) fertilizers by acquiring timely N status assessments of field plants through remote sensing techniques. To establish effective remote sensing models for plant N assessment, we carried out experiments using different rates of N fertilizer and examined changes in leaf anatomical characteristics, chlorophyll content and canopy reflectance behavior at the panicle initiation stage of paddy rice (Oryza sativa L. cv. Tainung 67). Results showed that plants with higher N content not only had higher chlorophyll content but also had thicker, flatter and more turgid leaves, which enhances visible light absorption while stimulating near-infrared reflection. Derivative type predictors, using the transition region from red and near-infrared wavebands, not only accounted for the changes in leaf chlorophyll content and structures induced by varied N content, but helped eliminate background soil interferences. Therefore, derivative type predictors may be more appropriate than reflectance values at specific band(s) and band ratios in establishing a robust model for plant N status assessment.