Nitrogen recommendations for corn where manure is applied are commonly made by subtracting a N credit for the manure from a total N recommendation calculated using the yield goal concept or the N Rate Calculator. Nitrogen availability from manure is difficult to estimate, and farmers are often thought to discount or ignore the N credits due to the uncertainty of the estimates. We used field records and cornstalk nitrate results from greater than 2000 field-years to evaluate the accuracy N credits from manure applications made by farmers to corn fields in Lancaster County Pennsylvania. The results show that N credits typically used by soil testing laboratories were poorly related to corn stalk nitrate N concentrations and amounts of manure reported by farmers. The results also revealed that when manure was applied for the growing season when the corn stalk nitrate was collected or when a field had a long-term history of manure applications there was a two fold increase in the probability of a field testing in a higher corn stalk nitrate category. The amount of N applied by the farmers as manure or fertilizer compared with the amount recommended by various soils testing laboratories indicated that the farmers are making substantially different estimates of N availability. The results of the corn stalk nitrate test suggest that neither the farmers nor the soil testing laboratories were capable of accurately estimating N availability from the manure. These data indicate the need to use corn stalk nitrate results, field-by-field records, which include previous crop, manure history, manure applications, and tillage for a number of years to make accurate estimates of N availability from manure.