Recently, a mobile NIR system has been commercialized for rapid mapping of the variations in soil spectra within a field. The Illinois Soil Nitrogen Test (ISNT) measures a fraction of mineralizable soil organic N. Measuring this pool and adjusting nitrogen rates accordingly has shown promise for improving corn fertilization efficiency. This study investigates the relationship between this fraction and the NIR spectra. In order to assess the feasibility of using NIR measurements to improve the cost-effectiveness of identifying ISNT levels, a multi-field study was completed.