Tillage practices, which have direct impacts on soil and water quality, have changed dramatically during the past several decades. Tillage information is one of the important inputs for environmental modeling, but the availability of this information is still limited spatially and temporally. Previous studies have encountered difficulties in defining reliable correlations between crop residue cover (CRC) and Landsat-based tillage indices because they neglected the significance of the timing of tillage implementation. This study explores relationships between temporal changes of agricultural surfaces and the normalized difference tillage index (NDTI) in Central Indiana. We found that minimum NDTI (minNDTI) values extracted from multi-temporal NDTI profiles reliably indicate the surface status when tillage or planting occurred. Simple linear regression reveals a coefficient of determination (R2) of 0.89 between CRC and minNDTI for calibration. In addition, a percentage change (PC) method was tested for classifying CRC into three categories (CRC