Two experiments, one focusing on preemergence (PRE) herbicides and the other on postemergence (POST) herbicides, were conducted and repeated in time to examine the utility of hyperspectral remote sensing data for discriminating common cocklebur, hemp sesbania, pitted morningglory, sicklepod, and soybean after PRE and POST herbicide application. Discriminant models were created from combinations of multiple indices. The model created from the second experimental run's data set and validated on the first experimental run's data provided an average of 97% correct classification of soybean and an overall average classification accuracy of 65% for all species. These data suggest that these models are relatively robust and could potentially be used across a wide range of herbicide applications in field scenarios. From the data set pooled across time and experiment types, a single discriminant model was created with multiple indices that discriminated soybean from weeds 88%, on average, regardless of herbicide, rate, or species. Signature amplitudes, an additional classification technique, produced variable results with respect to discriminating soybean from weeds after herbicide application and discriminating between controls and plants to which herbicides were applied; thus, this was not an adequate classification technique.
Nomenclature: Common cocklebur, Xanthium strumarium L.; hemp sesbania, Sesbania exaltata (Raf.) Rydb. ex. A.W. Hill; pitted morningglory, Ipomoea lacunosa L.; sicklepod, Sennna obtusifolia (L.) Irwin and Barnaby; soybean, Glycine max (L.) Merr.
Additional index words: Acifluorfen, chlorimuron, hyperspectral imagery, imazaquin, indices, metribuzin, pendimethalin, ROC curve.
Abbreviations: CCC, canonical correlation coefficient; DAA, days after application; DINO, differential index of normalized observations; LDA, linear discriminant analysis; NDVI, normalized difference vegetation index; NIR, near-infrared; POST, postemergence; PRE, preemergence; ROC, receiver operator characteristics; SA, signature amplitudes; SCA, species classification accuracy; SDM, single discriminant model; SWIR, short-wave infrared.
