Nitrogen loss
- Also known as
- nitrogen leaching, volatilization, denitrification
Nitrogen loss is the escape of applied or soil nitrogen from the crop root zone before plants can use it. The main pathways are nitrate leaching, denitrification to gases, ammonia volatilization and runoff, and losses reduce yield, waste fertilizer and can harm water and air quality.
What is nitrogen loss?
Crops need large amounts of nitrogen, but only part of the nitrogen applied as fertilizer or manure ends up in the crop. The rest may be stored in the soil or lost. Losses lower nutrient use efficiency, cost growers money and contribute to water pollution and greenhouse gas emissions.
Main loss pathways
| Pathway | What happens | Conditions that favor it |
|---|---|---|
| Leaching | Nitrate moves down with water below the root zone | Sandy soils, heavy rain or irrigation, nitrate present before crop uptake |
| Denitrification | Soil microbes convert nitrate to nitrogen gases, including nitrous oxide | Saturated, warm soils with low oxygen |
| Volatilization | Ammonia gas escapes from urea or manure left on the surface | Surface application without incorporation, warm, moist surfaces, high pH |
| Runoff and erosion | Nitrogen carried away with water and soil | Heavy rain, bare or sloping ground |
Nitrate is especially mobile because it is negatively charged and not held by the soil’s cation exchange capacity. Nitrous oxide from denitrification is a potent greenhouse gas.
How losses are reduced
The 4R framework guides nutrient stewardship: the right source, at the right rate, at the right time, in the right place. Practices include:
- Split applications that match nitrogen supply to crop demand.
- Incorporating or injecting urea and manure.
- Urease inhibitors, which slow volatilization, and nitrification inhibitors, which slow conversion to leachable nitrate.
- Cover crops that take up leftover nitrate.
- Drainage and irrigation management.
- Biological nitrogen fixation and other biological approaches that supply or retain nitrogen.
Frequently asked questions
Nitrate, which leaches readily and is the starting point for denitrification.
Not permanently. Soil microbes can temporarily tie up nitrogen as they break down high-carbon residues, then release it later.
Sources
- Nitrogen loss pathways and management, Land-grant university extension (e.g. University of Minnesota, Purdue University)
- The 4R Nutrient Stewardship framework, The Fertilizer Institute