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A prototype of an automated soil sampling system for on-the-go measurement of soil pH has been developed and evaluated (Papers No. 98-3094, 99-1100 & 01-1045). It was shown that automated mapping of soil pH using ion-selective electrodes (ISE) on naturally moist soil is an effective alternative to conventional manual grid mapping. In this work the feasibility of applying a similar technique to map potassium and nitrate-nitrogen content was tested. It was found that polymer membrane K+ and NO3 - ion-selective electrodes can be used to predict other analytical measurement methods (atomic absorption spectroscopy and cadmium reduction) commonly used in soil laboratories. Significant correlations (R2 = 0.56 - 0.94) were observed while using both direct and soil solution measurements. Obtained results represent snapshots of real-time availability of K+ and NO3 - ions in soil solution, which could be used as indirect indicators for adjusting variable application rates of potassium or nitrogen fertilizers in combination with other layers of spatial data.