If we apply N fertilizer or manure, often less than 100% of the applied inorganic N will be taken up by the corn, because of competition with other processes (e.g. leaching, denitrification, volatilization, immobilization, etc.). In order to account for the inherent inefficiency still present with good management, the N requirement should be adjusted. Given the array of N cycle processes involved with the efficiency by which N is utilized by the crop, this factor can vary from year to year. Through years of research across New York State, average N uptake efficiencies have been determined for every soil in the state.
The N uptake efficiency depends on the following factors.
The table, below, contains examples of N uptake efficiency for a range of soils in the Cornell database. Move your mouse over each of the soil names for a description of each soil.
To read more on this subject: Nitrogen Guidelines for Field Crops in New York (section 4.1)