Manure is not simply a waste product that needs to be disposed of, especially when fertilizer prices are high. The Penn State Manure N-P-K Economic Value Calculator makes the process of calculating manure nutrient value relatively simple.
With fertilizer prices remaining volatile and nitrogen (N) and phosphorus (P) fertilizer prices still relatively expensive, farmers are looking for economical ways to meet their crop nutrient needs. During the fall season, as crops are being harvested, soil samples collected, manure spread, and fertilizer purchases lined up, now is the time to consider the economic value that local manure can have as a replacement for fertilizer.
Manure is not simply a waste product that needs to be disposed of, especially when fertilizer prices are high. Properly managed manure is a source of nitrogen, phosphorus, potassium (K), organic matter, and other nutrients. The challenge is putting a realistic dollar value on those nutrients and determining whether manure makes economic sense compared with commercial fertilizer.
Penn State Extension’s Manure N-P-K Economic Value Calculator provides a simple way to do this.
What are manure nutrients really worth?
The basic concept behind the calculator is straightforward: manure has an economic value when it can replace fertilizer that you would otherwise need to purchase.
The calculator uses three pieces of information:
- The nutrient content of the manure, preferably from a current manure analysis, and nitrogen availability factors based on application method.
- The crop’s fertilizer requirements, based on a soil test and expected crop yield.
- The current price of commercial fertilizer.
The calculator then estimates the value of the N, P, and K supplied by the manure, with a breakdown for the total value of the manure nutrients if fully utilized in the long-term and an annual value when replacing the fertilizer recommendation for the next year of crop production.
The following example simplifies the calculation by just considering the phosphorus and potassium value of the manure, because these nutrients have availability equivalent to fertilizer and can be conserved in the soil for multiple years. The calculator also handles manure nitrogen value, but the fate of manure nitrogen is highly uncertain, depending on application management and cover cropping practices, so calculations should be tailored to individual scenarios using nitrogen availability factors from the Agronomy Guide.
The Penn State Agronomy Guide provides typical Pennsylvania manure nutrient concentrations that can be used as “book values” when an actual manure analysis is not yet available. These values are averages, not guarantees. Actual manure nutrient concentrations can vary substantially, which is why a laboratory manure analysis is preferred whenever possible.
In this example, consider the nutrient value of three common manure sources listed in Table 1.2-10 of the Agronomy Guide:
| Manure source | P₂O₅ | K₂O | Units |
|---|---|---|---|
| Dairy, liquid | 13 lb | 25 lb | per 1,000 gal |
| Swine, grow-finish, liquid | 24 lb | 22 lb | per 1,000 gal |
| Poultry, broiler (38-46 days) | 43 lb | 47 lb | per ton |
To estimate the economic value, consider current fertilizer prices. For this example, recent fertilizer prices in September 2026 of approximately $925 per ton for diammonium phosphate (DAP) and $495 per ton for potash are used. Because DAP contains both nitrogen and phosphorus, whether or not the nitrogen portion will be utilized towards meeting the needs of the crop should be accounted for when determining the true cost of the phosphorus. This is the type of adjustment made by the Penn State manure value calculator.
Using these fertilizer prices in the calculator, and assigning value to the N component of DAP, gives an approximate economic value of:
- $0.73 per pound of P₂O₅
- $0.41 per pound of K₂O
The resulting total P and K value of the three manure sources is then:
| Manure source | P₂O₅ value | K₂O value | Total P + K value |
|---|---|---|---|
| Dairy, liquid | $9.49/1,000 gal | $10.25/1,000 gal | $19.74/1,000 gal |
| Swine, grow-finish, liquid | $17.52/1,000 gal | $9.02/1,000 gal | $26.54/1,000 gal |
| Poultry, broiler (38-46 days) | $31.39/ton | $19.27/ton | $50.66/ton |
These numbers represent only the phosphorus and potassium value. No value has been assigned to the nitrogen, sulfur, micronutrients, organic matter, or other potential benefits supplied by manure.
For example, 5,000 gallons per acre of the representative dairy manure would contain approximately $99 worth of P and K at these fertilizer prices. The same application rate of the representative swine manure would contain approximately $133 worth of P and K. Two tons per acre of the representative poultry litter would contain approximately $101 worth of P and K.
Why local manure can be especially valuable
One of the advantages of manure is that it is often produced relatively close to the farms that need nutrients. A livestock farm may have more manure than it can efficiently use on its own acres, while a nearby crop farm may be purchasing commercial fertilizer. That creates an opportunity for both farms.
For the livestock farm, moving manure to a crop farm can provide a productive use and possible revenue stream for nutrients that would otherwise require additional land for application. For the crop farmer, locally available manure can provide nutrients at a cost that may be competitive with, or lower than, purchased fertilizer.
The economics depend on more than the nutrient value, however. Transportation and application costs matter. A manure source with a $51-per-ton fertilizer value is not necessarily economical if it costs $60 per ton to haul and spread. Conversely, manure that can be obtained and applied at a relatively low cost may provide substantial fertilizer savings.
Don’t overlook the nitrogen value
Nitrogen is often the largest fertilizer expense, and nitrogen fertilizer prices have been particularly volatile. Manure can provide an important source of nitrogen in addition to P and K. However, nitrogen is different from P and K because not all of the total manure N becomes available to the crop during the first growing season. Nitrogen availability depends on the manure’s ammonium and organic N content, application timing, incorporation, rainfall, and other management factors. The calculator accounts for these factors when estimating the fertilizer replacement value of manure N by entering ammonium and organic N availability factors from Table 1.2-12 of the Agronomy Guide based on your planned application practices.
This means you should not simply multiply total manure N by the price of fertilizer N. The economically useful number is the amount of manure N that can actually replace purchased fertilizer N. In another article, we discuss how increasing the ammonium N availability through manure injection significantly increases the economic value of manure N.
Soil testing is essential
There is one important qualification to all of these calculations: manure nutrients only have an economic value when the crop needs those nutrients.
If a soil test indicates that a field does not need additional phosphorus or potassium, applying manure because it contains “free” P and K does not necessarily save money. In fact, continued application of manure to a field with high soil-test phosphorus can create nutrient management and environmental concerns. Similarly, applying manure to legumes negates any economic value of N in the manure.
The economic value of manure should therefore be based on nutrients that replace fertilizer that would otherwise have been purchased. Using the manure nutrient value calculator to combine data from soil test-based nutrient recommendations, an actual manure nutrient analysis, and fertilizer prices helps you see the true value of manure for any situation.
Use the calculator before you buy fertilizer
The Penn State Manure N-P-K Economic Value Calculator makes the process of calculating manure nutrient value relatively simple. Enter the manure analysis—or appropriate book values if an analysis is not yet available—along with the crop’s nutrient requirements and current fertilizer prices. The calculator estimates both the potential value of the manure nutrients in the long-term and the immediate fertilizer replacement value for the next year’s crop.
This provides a practical way to put manure and commercial fertilizer on the same economic playing field. The next time fertilizer prices make the fertilizer bill look expensive, take a second look at the manure available nearby. It may be carrying considerably more fertilizer value than its appearance suggests.
Try the calculator: Manure N-P-K Economic Value Calculator
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