Code 614.4 Brown Bag Seminar

Speakers: Craig S. T. Daughtry and Paul. C. Doraiswamy USDA-ARS, Hydrology and Remote Sensing Lab, Beltsville MD Abstract Crop residues play important roles in reducing soil erosion and increasing soil organic carbon. Current methods of quantifying crop residue cover are inadequate for characterizing the spatial variability of residue cover within fields or across large regions. Our objectives were to measure crop residue cover and to categorize soil tillage intensity using satellite remotely sensed data in test sites in Iowa, Illinois, and Indiana. Hyperion imaging spectrometer and Landsat TM data were acquired in May and June 2004 over a test site in central Iowa. Crop residue cover was measured in corn and soybean fields using line-point transects. Spectral residue indices using Landsat TM bands were weakly related to crop residue cover. With the Hyperion data, crop residue cover was linearly related to the Cellulose Absorption Index (CAI), which is the relative depth of cellulose and lignin absorption features near 2100 nm. Coefficients of determination (r2) for crop residue cover as a function of CAI were 0.85 for the May 3 and 0.77 for the June 4 data. Three tillage intensity classes, corresponding to intensive (<15% residue cover), reduced (15-30% cover), and conservation (>30% cover) tillage, were correctly identified in 66-68% of fields. Classification accuracy increased to 80-82% for two classes, i.e., conventional (intensive + reduced) and conservation tillage. By combining information on previous seasons (2003) crop classification with crop residue cover after planting in 2004, an inventory of soil tillage intensity by previous crop type was generated for the whole Hyperion scene. Regional surveys of soil management practices that affect soil conservation and soil carbon dynamics are possible using advanced multispectral or hyperspectral imaging systems.