Corn Nitrogen Rate Calculator (Yield Goal Method)
Enter your yield goal, previous crop and credits to get a nitrogen rate in lb N per acre, then the pounds or gallons of urea, ammonia or UAN and the cost.
How to use the Corn Nitrogen Rate Calculator
- Enter Expected corn yield (bu/acre). K-State suggests about 105 percent of your three-to-five-year field average.
- Choose Water supply.
- Choose Previous crop; for alfalfa or clover, match your stand.
- Enter Soil organic matter (%).
- Choose N application method (default or high efficiency) and Risk of N loss (low or high).
- Choose Nitrogen source: anhydrous ammonia, urea, ammonium sulfate, UAN 28 % or UAN 32 %.
- Read Nitrogen rate (lb N/acre) and the product table, which lists pounds per acre of every source. For UAN, also read the gallons per acre.
- Optional: open More options to add a soil nitrate-N test (ppm) with Sampling depth (inches), Manure N (lb N/acre), irrigation water nitrate-N (ppm) with Irrigation water applied (inches), or Other N credits or N already applied (lb N/acre).
- Optional: enter Product price (optional) in $/ton ($/gal for UAN only) and Field size in acres (optional) to see cost per acre, cost per pound of N and field totals.
Four preset buttons fill in examples (such as 180 bu after soybeans with urea). How it was calculated shows each step with your numbers. Copy link keeps all your inputs, Copy result copies the output, and Print / save as PDF prints inputs, results, steps and the date. Reset clears the form.
How much nitrogen does corn need per acre?
The tool calculates a rate from your yield goal, water supply, previous crop, organic matter and optional credits. The result stays between 30 and 230 lb N per acre non-irrigated, or 300 irrigated. With the default inputs (180 bu, non-irrigated, 2 percent organic matter, after soybeans, no soil test) the rate is 178 lb N per acre, or 199.5 kg N/ha. The equation is written for Kansas, so treat the answer as a planning estimate and check your own state’s recommendation.
How do I calculate a nitrogen rate for corn from yield goal?
Multiply the yield goal by the N factor, subtract the credits and add the previous-crop adjustment. The equation is N = (ie / fe) × expected yield − se × profile N − 20 × % organic matter − manure N − other + previous crop adjustment. Here ie is 0.88 lb N per bushel non-irrigated (0.84 irrigated) and fe is 0.55 for default application (0.65 for high efficiency). With defaults, ie / fe is 1.6, so 180 bu gives 288 lb N before credits. The defaults then give 288 − 30 − 40 − 40 = 178 lb N per acre: 30 is the default profile N, the first 40 is the 2 percent organic matter, and the last 40 is the soybean credit.
How much nitrogen credit does soybean give to corn?
Soybeans give a credit of 40 lb N per acre. Corn, wheat, sorghum and sunflowers give no credit. Alfalfa credits depend on stand: excellent, good, fair and poor give −120, −80, −40 and 0. Red clover gives −80, −40 and 0 and sweet clover −110, −60 and 0 for excellent, good and poor stands. Fallow gives −20 without a soil nitrate test and 0 with one.
How do I use a soil nitrate test in the nitrogen rate?
Under More options, enter the soil nitrate-N result in ppm and the sampling depth in inches. The tool calculates profile N as 0.3 × depth × ppm, then multiplies it by se (1.0 for low risk, 0.7 for high risk). For example, 8 ppm over 24 inches gives 0.3 × 24 × 8 = 57.6 lb N, which is subtracted. If you leave ppm empty, the tool uses K-State’s default of 30 lb N per acre.
Sources
- Kansas State University MF2586, Soil Test Interpretations and Fertilizer Recommendations in Kansas (January 2024) — the corn nitrogen equation, efficiency factors, soil organic matter, soil nitrate, manure, irrigation water and previous-crop credits, and the 30 / 230 / 300 lb N limits
- CF Industries, UAN product specification (May 2022) — UAN 28 and 32 % N by weight and density at 60 °F, used for lb N per gallon
- Virginia Tech Extension 2908-1405 — urea 46 % N, ammonium sulfate 21-0-0-24S, UAN grades, and N rate ÷ lb N per gallon for UAN
Worked examples
| Input | Result |
|---|---|
| 180 bu/ac non-irrigated, 2 % SOM, previous crop soy, urea | 178 lb N/ac (199.5 kg N/ha), 387 lb product/ac |
| 200 bu/ac irrigated, 3 % SOM, previous crop corn, uan32 | 100.9 lb N/ac (113.1 kg N/ha), 315.2 lb product/ac, 28.4 gal/ac |
| 160 bu/ac non-irrigated, 2 % SOM, previous crop alfG, nh3 | 115 lb N/ac (128.9 kg N/ha), 140.2 lb product/ac |
| 250 bu/ac non-irrigated, 1 % SOM, previous crop corn, urea | 230 lb N/ac (257.8 kg N/ha), 500 lb product/ac |
Calculated by the tool above with these values.
Frequently asked questions
How many pounds of urea or anhydrous ammonia per acre for 150 lb N?
Divide the N rate by the N percentage of the product. Urea is 46 percent N, so 150 ÷ 0.46 ≈ 326 lb per acre. Anhydrous ammonia is 82 percent N, so 150 ÷ 0.82 ≈ 183 lb per acre.
How many gallons of UAN per acre for a nitrogen rate?
Divide the pounds of N by the pounds of N per gallon. UAN 28 percent holds 2.99 lb N per gallon, so 150 lb N needs about 50.2 gallons. UAN 32 percent holds 3.55 lb N per gallon, so the same rate needs about 42.3 gallons.
How much is manure N worth for corn?
Manure N is counted at 100 percent, so each pound you enter under Manure N (lb N/acre) lowers the rate by one pound. Take the value from the K-State manure worksheet (MF2562).
What does nitrogen cost per pound of N from urea vs UAN vs ammonia?
Cost per pound of N depends on your product price, so the tool works it out from the price you enter. Enter $/ton for urea or ammonia, or $/gal for UAN only. A ton of urea (46 percent N) holds 920 lb N, and a ton of anhydrous ammonia (82 percent N) holds 1,640 lb N. For example, UAN 32 at $2.10 per gallon costs about $0.59 per pound of N (2.10 ÷ 3.55).
Is the calculator free, and is anything I type uploaded?
Yes, the calculator is free. It runs in your browser, nothing you type is uploaded, and no sign-up is needed.
Related tools
- Fertilizer Calculator: use it to work out product amounts for nutrients other than nitrogen.
- Corn Yield Calculator: use it to estimate the yield you should set as your goal.
- Lime Calculator: use it when your soil test points to a liming need.
- Seeding Rate Calculator: use it to set seed population and seeding rate for a planting.
- Acreage Calculator: use it to find the area of a field before you enter a field size.
- Sprayer Calibration Calculator: use it to check how much product your sprayer applies per acre.
- Soybean Yield Calculator: use it when you are planning a soybean crop, which may come before corn in your rotation.
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