Two commercially available ion exchange resin (IER) devices—Unibest resin capsules (Unibest, Inc., Bozeman, MT) and Plant Root Simulator (PRS) probe–ion exchange membranes (Western Ag Innovations, Inc., Saskatoon, Canada)—for measuring soil nutrient availability were compared to traditional soil NH₄⁺ and NO₃⁻ measurements during incubation of an Oklahoma tallgrass prairie soil at two temperatures (16° and 25°C) and two moisture contents (15 and 25% by weight). Nitrate dominated the soil mineral N pool in soils and in both IER devices. Soil extractable and resin capsule mineral N showed significant responses to both temperature and moisture whereas PRS probe mineral N showed responses to moisture only. Both devices were more sensitive to moisture than soil mineral N was. Neither device related well to N mineralization or the patterns of extractable mineral N over time. Possible reasons for the differences include the integration of soil mineral N over time in the IERs as opposed to snapshots in time for soil mineral N, spatial variation within the incubated soils, and the importance of solution contact with IERs.