ABSTRACT

Remotely sensed images contain site-specific information about conditions in agricultural fields. Researchers have developed several indices that use information extracted from images to represent plant growth status. The normalized difference vegetation index (NDVI) is a commonly used one for agricultural applications. The aim of this study was to identify the relationships among remotely sensed NDVI, weed intensity levels measured at ground level, and plant canopy coverage measured at ground level, all in one cotton field in the Mississippi Delta. Four-band images of the study site were acquired by Geodata Inc. with their GeoVantage^® imaging system. The blue band is centered at 450 nm, the green band at 550 nm, the red band at 650 nm, and the near-infrared band at 850 nm. A mosaic image was created from individual scenes with the Erdas Imagine mosaic tool. The resulting image resolution was approximately 0.5 m. A ground-based weed mapping system was developed to measure the weed intensity and distribution in a cotton field. The weed mapping system includes WeedSeeker^® PhD600 sensor modules to indicate the presence of weeds, a GPS receiver to provide spatial information, and a data acquisition and processing unit to collect and process the weed data and spatial information. Crop canopy coverage data were collected at approximately the same time as image acquisition and mapping of weed intensity levels. Results indicated that both weed intensity level and crop coverage were significantly correlated with NDVI, and that weed intensity levels should be considered when NDVI is used to predict crop growth and development.