Urea Volatilization & Nitrogen Lost as Ammonia
Loses ammonia
Enter your urea rate and the conditions to estimate the nitrogen and urea lost as ammonia gas and what's retained — so you know the cost of surface-applying urea and when to incorporate it.
Estimate ammonia loss
Next: incorporate or irrigate after applying urea to cut volatilization — you stand to lose 11.5 kg N (25 kg of urea) if it sits on the surface.
Surface losses climb with heat, wind, high soil pH and crop residue; a urease inhibitor or watering it in within a day or two can sharply reduce them.
Urea volatilization — key facts
- Loss as ammonia
- up to 25–40%
- Worst on
- warm, moist, high-pH soil
- Trigger
- left un-incorporated
- Urea is
- ≈ 46% nitrogen
- Best fix
- incorporate or wash in
- Wash-in
- ≈ 10–15 mm rain/irrigation
- Coated urea
- neem / urease inhibitor cuts loss
- Privacy
- Runs in your browser; nothing uploaded
The nitrogen you can't see leaving still costs you money
Urea is the cheapest nitrogen by the kilogram, but only if it stays in the soil. Spread on a warm, moist, high-pH surface and left un-incorporated, a big share of its nitrogen escapes invisibly as ammonia gas — losses can reach 25–40% before the crop ever uses it. You pay for the bag, but a quarter to nearly half of the nitrogen blows away. A volatilization estimate settles it with numbers — how much nitrogen you applied, how much is lost, and how much is actually retained.
This tool gives the nitrogen applied, nitrogen lost, nitrogen retained and the urea effectively wasted from your rate and the conditions. Use it to decide whether to incorporate or wash urea in, to value neem-coated urea and deep placement, and to time top-dressing before rain. Pair it with the Neem-Coated Urea Saving, Urea Briquette Deep Placement and Fertilizer Split Dose tools for a full nitrogen plan.
See the real cost
Know the nitrogen and urea lost to the air.
Time it right
Wash urea in with rain or incorporate it.
Value coated urea
Compare losses against neem-coated options.
Keep more nitrogen
Hold N in the soil for the crop, not the sky.
Frequently Asked Questions
What is urea volatilization?+
When urea is spread on the soil surface it is converted by the enzyme urease into ammonium, but some of that nitrogen escapes into the air as ammonia gas before plants or soil can hold it. That loss is called volatilization, and it is wasted nitrogen — you pay for the urea but the crop never sees it.
How much nitrogen can be lost?+
Surface-applied urea left un-incorporated can lose 25–40% of its nitrogen as ammonia under bad conditions — warm, moist, high-pH soils with little rain or irrigation to wash it in. The calculator estimates the N lost, the urea effectively wasted, and the N actually retained for the crop.
What conditions make volatilization worse?+
Heat, surface moisture without infiltration, high soil pH (calcareous soils especially), low cation-exchange capacity, crop residue on the surface, and wind all increase loss. The worst case is urea broadcast onto a warm, damp, limey, residue-covered surface on a still, drying day.
How do I reduce urea loss?+
Incorporate urea into the soil by tillage, drilling or banding, or wash it in with 10–15 mm of rain or irrigation within a day or two of spreading. You can also switch to neem-coated or urease-inhibitor-treated urea, or place urea briquettes below the surface — all of which keep more nitrogen in the soil.
Does rain or irrigation help?+
Yes — moving urea below the surface is the single biggest fix. A good rain or irrigation of roughly 10–15 mm soon after application dissolves the urea and carries it into the soil where the ammonium is held on clay and organic matter, sharply cutting ammonia loss. A light dew that only dampens the surface can make loss worse.
Why does soil pH matter so much?+
Ammonia escapes more readily as the soil becomes more alkaline. Urea hydrolysis itself raises pH around each granule, and on already high-pH or calcareous soils that pushes the balance toward gaseous ammonia rather than ammonium held in the soil — so high-pH soils lose the most when urea is left on top.
What does 'urea wasted' mean here?+
It is the amount of urea fertiliser whose nitrogen escaped as ammonia — effectively the bag you paid for but the crop never received. The calculator converts the nitrogen lost back into kilograms of urea so you can see the real cost of surface application and judge whether incorporation is worth it.
Does it work for any rate or unit?+
Yes — enter the urea rate per acre or hectare and the conditions, and it estimates N applied, N lost, N retained and urea wasted. Urea is about 46% nitrogen, so the calculation scales cleanly to any application rate and area you farm.
Are the figures precise?+
They're solid planning figures. Real volatilization depends on weather, soil and timing that shift hour by hour, so treat the loss as a range, not an exact number. Use it to compare leaving urea on top against incorporating it — the message is steering, not exact prediction.