Managing soil for agricultural production without tillage is considered sustainable and environmentally beneficial. In Brazil and in the USA the no-tillage system is used on over 20 Mha. Nitrogen fertilization is a major concern in no-tillage, for both economic and environmental reasons. Most fertility recommendation systems do not include specific soil parameters to determine the amount of N to be applied. A few recommendation systems include soil organic matter and/or soil nitrate. Our objective was to evaluate several methods of assessing N mineralization and determine how they could be used to parameterize currently available N simulation models. Forty-four soil samples from field plots under different tillage management systems located in various ecological regions of the southern USA were analyzed with chemical and biological procedures to predict N mineralization. Methods included: calcium hypochlorite oxidation, hot and cold 2 M KCl extraction, short-term anaerobic incubation, CO₂ evolved during three days, soil microbial biomass, near infrared reflectance spectrophotometry, total C and N by dry combustion, and non-leached long-term aerobic incubation. Results from the different procedures and their correlation to potentially mineralizable N will be presented.