Sustainable agriculture requires innovative and practical tools to optimize farm economics, conserve soil organic matter, and minimize negative environmental impacts (Johnson et al., 2003). Electromagnetic induction soil conductivity sensors may provide one such tool. Electromagnetic techniques are well suited for mapping soil conductivity to depths useful for agriculturalists (McNeill, 1990). Electrical conductivity (EC) methods have been shown to be sensitive to high nutrient levels (Eigenberg et al., 1996, 2000) and have been used to detect ionic concentrations on or near the soil surface resulting from eld application of cattle feedlot manure. EC has generally been associated with determining soil salinity; however, EC also can serve as a measure of soluble nutrients (Smith and Doran, 1996) for both cations and anions, and is useful in monitoring the mineralization of organic matter in soil (De Neve et al., 2000). Doran et al. (1996) demonstrated the predictive capability of soil conductivity to estimate soil nitrate.