Hyperspectral characteristic analysis of a developing cotton canopy under different nitrogen treatments

The objective of this study was to analyze the differences of crop agronomy parameters, canopy spectral reflectance and spectral indices induced by different nitrogen application rates, and to assess the potential of discriminant analysis in discriminating cotton canopies at different nitrogen treatments. We conducted an experiment in cotton fields treated with four nitrogen application rates: 0%, 50%, 100% and 200% of the recommended rate. Results suggested that no single spectral index or canopy variable can fully characterize the canopies nitrogen status throughout the growing period. With a single vegetation index, discriminant analysis provided less than 45%, 48.8%, 61.6% accurate classifications of cotton canopies by nitrogen treatment during early, mid and late season, respectively. Nevertheless, using multi-vegetation-index model by stepwise procedure, 74.4%, 83.1% and 89.6% accuracies could be obtained during early, middle and late season, respectively.