Investigation on the Potential of using ASTER Image for Corn Plant Residue Coverage Estimation in Three Indiana Counties

The purpose of this study was to investigate the use of remotely sensed imagery from the NASA Earth Science Enterprise (ESE) suite of satellite sensors to map crop residue and tillage practices. The U.S. Department of Agriculture´s (USDA) Natural Resource Conservation Service (NRCS) is doing biennial national residue mapping. Due to the high costs involved, only a small number of fields could be surveyed. Also the methodology is subjective. Using remotely sensed imagery may help to reduce the costs, allow many more fields to be used in the program, as well as potentially increase accuracy. This investigation used the Advanced Spaceborne Thermal Emission and Reflection Radiometer sensor (ASTER) for large area crop residue mapping. Residue covers from 421 corn fields within three Indiana counties were estimated following a windshield survey approach. The field level residue covers were divided into three levels: fields with >30% residue cover were classified as conservation tillage (no till); fields with 16-30% residue cover as reduced tillage; and fields with <15% residue cover as conventional tillage. Field mean spectral reflectance was extracted and several indices were calculated. The field level spectra and indices were then used in a discriminant analysis process. The results indicated that the ASTER Normalized Shortwave Index (ANSI) performed the best in separating no till from the combined conventional and reduced till fields. The average accuracy was 85.5% for all three counties with Huntington County having the best accuracy at 91%. In addition, pixel based supervised classifications were also implemented. The results showed that the shortwave near-infrared (SWIR) bands produced better classification accuracies than the visible near-infrared (VNIR) bands. While the use of ASTER images for corn residue mapping shows its potential, prior knowledge of the previous crop type is needed for successful operations.