Crop N Guidelines: Fertilizer N Uptake Efficiency

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.

• Soil type: soils vary in texture, drainage, native fertility, organic matter, structure, temperature, etc. Referring back to the N cycle, these are all factors that influence N availability in the root zone and, subsequently, N uptake by plants.

• Artificial drainage (drained or undrained): poor drainage limits N availability and the ability of plants to uptake N. The presence or lack of artificial drainage (e.g. tile drainage) in a field may shift the N uptake efficiency, depending on the native drainage of the soil.

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).