Optimal Vegetation Indices for Winter Wheat Growth Status Based on Multi-Spectral Reflectance

Abstract

In order to select appropriate vegetation indices for winter wheat, field experiments with four levels of N-fertilizer (0, 30, 60, and 90 kg ha⁻¹) in two repetitions were conducted for three years. Hyper-spectral reflectance data using a portable field spectroradiometer (351 to 2,500 nm) were recorded from 10 am to 2 pm under cloudless conditions at two different growth stages of winter wheat. All two-band and three-band combinations of several vegetation indices were subsequently calculated in an algorithm for determining linear regression analysis against SPAD value, protein content, and grain yield. R square matrices were used to make contour plots and 3-D scatters. Using overlaying in analysis tools of ArcMap the between first and second year results, a number of common hot spots with strong correlations were revealed. The selected hot spots were validated with the dataset of the third year to choose the best vegetation indices for crop variable estimations.