Soil color, organic matter content, and adsorption of the pesticide diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] were measured for the silt loam or silty clay loam Ap and Bt or Bg horizons of two toposequences of soils occurring within the same soil landscape in Tippecanoe Co., IN. Close linear relationships (r² > 0.9) were obtained between Munsell value, organic matter content, and diuron adsorption. Color-organic matter relationships within this landscape appear to be much better than previously reported relationships developed for soils over wider geographic areas. Sensors for measuring soil organic matter content as equipment moves across a field are more likely to be successful if they are calibrated on a field by field basis rather than utilizing relationships developed over a wide geographic area. Purdue Univ. Agric. Exp. Stn. Journal no. 11 140. Present addresses: R.N. Fernandez, Laboratorio de Fotointerpretacion, Facultdad de Agronomia-UBA, Avda. San Martin, 4453, 1417 Buenos Aires, Argentina; D.L. Coffin, American Cyanamid Co., Agric. Div., 24 Carriage Dr., Willow Street, PA 17584.