Long‐term aerobic incubations were conducted on soils previously amended with cow and poultry manure, sewage sludge, and mycelium to determine N mineralization potential (No) and N mineralization rate constant (k). Values for No were higher than those reported by other workers. The k values varied among soils sufficiently so that a single value could not be assumed for any one group of soils. Corn (Zea mays L.) was grown on five of the soils used in the incubation study. Soil moisture and soil temperature data from NoN0 and initial mineral N, estimates of N available to the crop. Yield and N uptake correlated well with the parameter No × k, but No alone proved to be a very poor predictor of yield or N uptake. K values, which can be estimated only from lengthy incubations, are required to obtain accurate estimates of N availability.

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