Nitrogen Calculator
Estimate crop nitrogen requirement, soil and rotation credits, manure contribution, fertilizer efficiency, and final product needed across the whole field.
Use this as a planning calculator before final nutrient recommendations. Local university guidance, soil test labs, irrigation, rainfall, timing, and nutrient regulations can change the field-ready nitrogen rate.
Nitrogen Plan Results
Calculated from the selected crop demand, soil nitrate, organic matter, previous crop, manure credit, fertilizer source, and efficiency.
| Crop | Yield unit | Base N | N per yield unit | Planning note |
|---|---|---|---|---|
| Corn grain | bu/ac | 20 lb/ac | 0.95 lb/bu | Use realistic yield goal and credit legume rotation. |
| Corn silage | tons/ac | 35 lb/ac | 8.0 lb/ton | High biomass removal often needs strong manure accounting. |
| Winter wheat | bu/ac | 25 lb/ac | 1.1 lb/bu | Split fall starter from spring topdress where appropriate. |
| Barley | bu/ac | 20 lb/ac | 0.9 lb/bu | Malting barley can be protein-sensitive. |
| Canola | bu/ac | 35 lb/ac | 1.8 lb/bu | Often responds to sulfur along with nitrogen. |
| Grass hay | tons/ac | 0 lb/ac | 40 lb/ton | Multiple cuts may justify split application. |
| Credit source | Typical range | Calculator field | How to improve accuracy |
|---|---|---|---|
| Soil nitrate | 0 to 80 lb N/ac | Direct lb N/ac entry | Use recent soil test depth recommended for the crop. |
| Organic matter | 12 lb N/ac per 1% | Organic matter percent | Use lab OM values instead of county averages. |
| Previous legume crop | 20 to 80 lb N/ac | Previous crop credit | Adjust for stand quality, termination timing, and regrowth. |
| Manure or compost | 10 to 120 lb N/ac | Available manure credit | Base credit on manure test, rate, incorporation, and timing. |
| Irrigation nitrate | Site specific | Add to soil nitrate | Include irrigation water nitrate when lab data is available. |
| Fertilizer source | N analysis | Product for 100 lb N | Useful note |
|---|---|---|---|
| Urea | 46% | 217 lb product | Protect surface-applied urea from volatilization losses. |
| UAN 28 | 28% | 357 lb product | About 34 gal of UAN 28 before efficiency adjustment. |
| UAN 32 | 32% | 313 lb product | About 29 gal of UAN 32 before efficiency adjustment. |
| Ammonium nitrate | 34% | 294 lb product | Fast-available N where permitted and available. |
| Ammonium sulfate | 21% | 476 lb product | Adds sulfur but increases product tonnage. |
| Anhydrous ammonia | 82% | 122 lb product | Requires proper injected application equipment. |
| Efficiency factor | Meaning | Field situation | Effect on product |
|---|---|---|---|
| 95% to 100% | Very low expected loss | Injected, incorporated, or well-timed fertigation | Product stays close to net N need. |
| 85% to 90% | Moderate planning factor | Common sidedress, topdress with timely rain, banded application | Product rises modestly to cover expected loss. |
| 70% to 80% | Higher loss risk | Warm surface urea, sandy soil, wet spring, delayed uptake | More product is required for the same available N. |
| 50% to 65% | High uncertainty | Leaching-prone, denitrification-prone, or poorly timed application | Consider split timing instead of simply adding more N. |
Before applying: Confirm the soil nitrate depth, manure availability factor, and previous crop credit with local guidance. Small credit errors become large product changes across many acres.
Before increasing rates: Check whether timing, placement, stabilizer, or split application can improve efficiency. Better recovery often beats adding extra fertilizer product.
Nitrogen is essential for crop because crop require large quantities of nitrogen to grow. The level of nitrogen in the soil must also be carefuly manage because too much or too little nitrogen will impact the crop and the finances associated with growing those crop. To determine how much nitrogen the crop require, it is also necessary to determine how much nitrogen is already present in an soil.
Nitrogen may be present in the soil in several ways; nitrogen can be contained within the soil itself, it may have been deposited by previous crop, or it may be contained within manure in the soil. Each of these component can be accounted for in determining the amount of nitrogen that is already in the soil to be subtracted from the total nitrogen requirement of the crop. One way of determining how much nitrogen may already be contained in the soil is through the use of soil nitrate test.
Check Soil Nitrogen and Plan Fertilizer Use
Soil nitrate tests are indicative of the amount of nitrogen that is already in a form that can be used by the crop. Deep and recent soil sample can be taken to provide a more accurate measurement of the amount of nitrogen that is in the soil. Organic matter contain nitrogen, but releases it slow over time.
The rate at which organic matter releases nitrogen can vary depending upon factor like temperature, moisture of the soil, and the tillage of the soil. Additionally, the crop that were grown in the soil prior to planting the crop to be managed for nitrogen can contribute to the nitrogen in the soil. For instance, legume crop often contain a large amount of nitrogen credit.
However, previous crop may overestimate the amount of nitrogen credit that may be provided if those previous crop were thin stand or were terminated later in there growing season. Manure deposit also provide nitrogen credit to the soil. However, like other factor that impact the soil, the amount of nitrogen that can be released from manure into the soil also depend upon factor like the time at which the farmer applied the manure to the soil, how deep the manure was incorporated into the soil, and the nitrogen content of the manure itself.
The amount of nitrogen credit from manure can be entered into a nitrogen calculator. The amount of nitrogen that the crop will require after accounting for the amount of nitrogen that is in the soil, contributed by previous crop, and contributed by manure will be the amount of nitrogen that fertilizer will supply. Additionally, adjustment will be necessary to account for the efficiency of the fertilizer.
The efficiency of the fertilizer relate to the amount of nitrogen that is actualy supplied to the crop by the fertilizer. High level of fertilizer efficiency suggest that the fertilizer is being applied in a way that a large portion of the nitrogen will actually reach the crop. High fertilizer efficiency will lead to the suggestion that you should apply less fertilizer product than if the fertilizer have low efficiency.
The opposite relationship also exist between fertilizer efficiency and the amount of fertilizer that should be applied. The efficiency of the fertilizer can be entered into the nitrogen calculator, but the decision must also be made as to whether the percentage of efficiency is set up in the calculator to reflect the fertilizer efficiency in the field to be treated. Fertilizer have different characteristic that allow for some fertilizer to be used in different way than others.
For instance, liquid fertilizer can often be applied to field in ways that solid fertilizer can not be applied. Anhydrous ammonia contain a high percentage of nitrogen, but require specific equipment to apply the fertilizer to the field, and specific soil condition to apply anhydrous fertilizer. The nitrogen calculator can help determine the amount of each type of fertilizer that will be required for the field.
Additionally, using a nitrogen calculator can help compare the different fertilizer source to determine the cost of each fertilizer per acre. The condition in the field may differ from theoretical condition for fertilizer efficiency. Factor like precipitation, soil texture, soil compaction, and the amount of nitrate contained in the irrigation water can all change the outcome of nitrogen fertilizer efficiency.
In such a case, the information from the nitrogen calculator can help create a baseline for the amount of nitrogen fertilizer that should be applied to the field; however, you can make adjustment to recommendation from the university, soil test, and observation of the field according to these changing factor. It is common to make mistake with the estimation of the nitrogen in the soil. One of the most common error is to fail to account for the effect of management or weather on the amount of nitrogen that will be able to be recovered by the crop.
Instead, if calculation indicate the need for a large amount of fertilizer to supply the crop with the nitrogen that it require, it may be beneficial to consider the efficiency of the fertilizer. For instance, increasing the efficiency of the fertilizer will have a greater impact on the economics of the farming operation than will increasing the rate at which nitrogen fertilizer is applied. Thus, you will make the decision to enter each parameter into the fertilizer calculator with the intention to determine the amount of nitrogen that the crop will need, and then to make a decision as to whether the suggested plan is sensible according to the condition of the field.
