Análise quantitativa de nitrogênio foliar na cultura do milho a partir de dados de espectroscopia de reflectância

The aim of this study was to evaluate the possibility of using reflectance spectroscopy to quantify leaf nitrogen concentration in irrigated corn. The experimental design was randomized blocks, in split plot parcels replicated four times, with the main plot composed of four levels of soil moisture solo L1=120%, L2=100%, L3=80% e L4=70% of the water requirement, based on field capacity (CC) and the subplot with four levels of nitrogen fertilization (N1= 0 kg, N2= 60 kg N3= 120 kg e N4=180 kg de N per hectare). To development of the vegetation index spectral measurements were made using the spectroradiometer FieldSpec Pro and determined to leaf nitrogen concentration. The measurements were performed in the laboratory for index calibration and in the field for validation. The index (NDSI) was obtained by linear regression between all possible normalized band ratio combinations and leaf nitrogen, where the index with the highest coefficient of determination (R²) was selected. The most promising normalized ratio was between 755 nm and 676 nm (R²= 0.704). The region located between 670 nm and 800 nm showed promise for obtaining spectral bands for N-related index formulation. Models similar to those obtained by NDSI have the potential to development of vegetation indexes that allow the quantification of nutritional status of plants from hyperspectral data