| Hand-held and aerial imagery were collected in two soybean fields in 2001 and 2002 to determine the utility of remotely sensed data for distinguishing sicklepod, pitted morningglory, entireleaf morningglory, horsenettle, and soybean. For hand-held data, discriminant models were created using multiple indices. From the pooled data set over years and locations, classification accuracies ranged from 29 to 99%. Nearly all wavelengths found for discriminating sicklepod, pitted morningglory, entireleaf morningglory, horsenettle, and soybean were located in the near-infrared portion of the electromagnetic spectrum. For aerial images, weed maps were constructed using total weed species at ground data sampling point. Using weed maps as reference, aerial image classification accuracies were 81 to 90% correct.; Weed population estimates were collected in two fields in 1997 to 1999 and 2001 to 2002 to determine if previous years' weed populations could predict future infestations. The strongest correlations occurred with 1997 data to predict 1998 and 2001 to predict 2002 sicklepod populations. In addition, greater than 84% agreement was found for these years on one field. Stronger correlations in sequential years is to be expected due to more inherent variability present between distant years than sequential years. Overall, morningglory spp. populations were weakly correlated between years. Using 1998 population data to predict 1999 horsenettle infestations at the same spatial location resulted in correlations up to 0.76.; Two soybean fields were monitored in 2001 and 2002 to determine the ability of multispectral imagery to be used for locating and classifying crop anomalies. Three image collection dates per location for each year was used in the supervised classification analysis. Crop anomalies included planter problems, soil problems, weed escapes, and stressed soybean plants in general. Accuracies for using remotely sensed data as a scouting tool ranged from 50 to 100%. As the number of anomalies observed from aerial imagery decreased, the number of anomalies found from directed scouting increased, thus providing higher accuracies in the latter part of the growing season. |
