The present study is focusing on the following main objectives that are: 1) to compare the spectral and radiometric characteristics of AVIRIS data from Alfalfa crops with the spectra measured by FieldSpecR ASD radiometer; 2) to study the impact of growth regulators that applied on alfalfa in comparison of data collected from AVIRIS seen and; 3) to build a spectral library for the alfalfa crop that exposed to growth regulators that were studied.
AVIRIS data from Blythe were acquired in June 1997 to study the agricultural spectra from different crops and for identification of crops in other areas with similar environmental factors and similar spectral properties. On June 26-28, 2001 spectra were collected from Alfalfa fields using the FieldSpecR ASD spectrometer at Blythe area, California (at the 114o 33.52 W Longitude and 33o 39.76 N Latitude to Longitude 114o 33.54 W and Latitude 33 39.88 N). The alfalfa crop fields were treated with different chemicals of growth regulators. These growth regulators were AuxiGro, Apogee and Messenger. These chemicals were used in different concentrations. Environmental parameters were studied such as the soil water content (WC), pH, and organic matter (OM).
The results of this study showed that there is a significant correlation between the data that were collected by AVIRIS image scene in 1997 and spectral data collected by the FieldSpec spectrometer in the same places that were scanned by AVIRIS. This correlation allowed us to build a spectral library to be used in ENVI-IDL software. Furthermore, using IDL algorithms of Spectral Angle Mapper classification (SAM), Spectral Feature Fitting (SFF) and Spectral Binary Encoding (SPE) showed an excellent agreement between the traced spectra from the AVIRIS image and the spectral radiometer data collected from the alfalfa crops treated with growth regulators (i.e. the correlation is between 75 - 94% match). Three widely used vegetation indices such as NDVI, WBI, and PRI, showed that there are significant correlations between WBI and NDVI (r2= 0.44 - 0.88 for alfalfa crops treated by growth regulators. Further use
of the AVIRIS images can be of a value to crops identification or crops yield for commercial use.