The nitrogen mineralized from soil organic matter is a major N credit that should be considered when making a plan for corn fertilization. Soil N is the average amount of N that becomes plant available from soil organic matter every year. The availability of the soil N depends on a couple major factors.
The table, below, contains examples of soil N availability for a range of soils in the Cornell database. Move your mouse over each of the soil names for a description of each soil. Why does the amount of N available from soil organic matter vary across the soil types in the table?
To read more on this subject: Nitrogen Guidelines for Field Crops in New York (section 3.1)