Currently, N fertility for rice and wheat production in Arkansas is based on criteria such as yield goal, cultivar, planting date, prior crop, and/or soil texture. With this approach, mineralization of soil N is not accounted for, and over or under application of N fertilizers could occur. Recently, it was reported in Illinois that the amino sugar-N in the soil could be used to predict the amount of soil mineralizable N. The objective of this study was to evaluate the ability of the Illinois Soil N Test (ISNT) and a modified acidified KMnO₄ method to predict the total N uptake of rice and wheat and ultimately the N fertility rates required by rice and wheat to optimize grain yield. Nitrogen fertilizer rate trials were conducted at multiple sites for both rice and wheat in 2003 and 2004. Soil samples were collected at 10 cm depths prior to preflood and spring applications of N fertilizers for rice and wheat, respectively. Samples were analyzed for mineralizable-N using the ISNT and a modified acidified KMnO₄ extraction. Both methods were correlated to total N uptake and grain yield of rice and wheat. This research will be used to calibrated the amount of fertilizer N required for a given soil N test to result in an optimum total N uptake to produce a maximum grain yield.