Calculating the Value of Nutrients in Manure

Calculating the Value of Nutrients in Manure

“How much is this manure worth?” This is a common question from both livestock farmers who are supplying manure and crop farmers who are utilizing it. To answer this question, it is important to understand the difference between gross value and net value. The gross value of manure reflects the equivalent commercial fertilizer value of the nutrients contained in the manure. The net value considers the impacts of application method, transportation, and cropping system nutrient needs as well as intrinsic values that are much more difficult to put a number on. Therefore, this article will focus on determining the gross value of nutrients in manure. This article will walk you through the steps to calculate your manure value, but the University of Nebraska has an Excel based spreadsheet tool that also works.

The value of manure depends upon:

  • the manure type,
  • how and where the manure is applied,
  • the amount of nutrients that the field needs for the next crop or crops, and
  • the cost of fertilizer.

Determining Commercial Fertilizer Costs in $/pound of Nutrient

Table 1. Some common commercial fertilizers and primary nutrient composition.
Fertilizer Product% of Primary Nutrient
Urea 46% Nitrogen (N)
32% UAN 32% Nitrogen (N)
MAP 52% Phosphorus (P)
Potash 60% Potassium (K)
Bentonite sulfur 85-90% Sulfur (S)
Zinc Sulfate 36% Zinc (Zn)

The first thing we need is the cost of fertilizer, which will have to be obtained from your local fertilizer dealer as prices vary between dealers. Once the price is known, you will need to know the percent of nutrient in the fertilizer product. Some common fertilizers are in the table to the right. With this information, we can get a price per pound of nutrient. The equation to do that is: Price of Fertilizer / 2000 lbs / percent of actual nutrient (as a decimal) = price of nutrient per pound

If urea is $775 per ton, then the price you’re paying for nitrogen when buying urea is:

$755 / 2000 lbs / 0.46 = $0.84 per pount of N

This worksheet is a guide to the math for calculating price per pound of nutrient. This process would need to be repeated for each nutrient.

Manure Nutrient Availability

Table 2. Example Beef Manure Nutrient Analysis
Lbs of nutrient
per ton (as is basis)
Ammonium Nitrogen 1.4
Organic Nitrogen 12.9
Phosphorus (P2O5) 12.7
Potassium (K2O) 12.5
Sulfur 2.8
Zinc 0.2

The next step in determining a manure value is to determine how much of our manure nitrogen is available. A number of factors influence this, including the temperature at the time of application, whether the product was incorporated, and the type of animal and housing that the manure came from. For this reason, different places have different availability factors.

Table 3. Fraction of organic nitrogen available this year.
Beef/Dairy Manure
Solid or Stored liquid 0.40
Composted feedlot 0.15
Poultry Manure
Layers with no bedding 0.45
All other poultry 0.40
Swine Manure 0.40

Here in Nebraska, UNL research shows that for most species about 40% of the organic nitrogen in manure is available the first year with an additional 35% becoming available over the following 3 years (See table 3).

For this example, I’m using a sample of beef manure with about 13 pounds of organic nitrogen, which calculates to about 5 pounds per ton the first year and another 4 and a half in the next few years.

13 pounds Organic N in manure times 40% available (from table 3) equals 5 pounds of N available this year

13 pounds Organic N in manure times 35% available (over next 3 years) equals 4.5 pounds of N available in the future

5 lbs N available this year plus 4.5 pounts N available in future equals 9.5 pounds of N of value

Ammonium nitrogen is only available the first year and is more easily lost to the atmosphere, which affects its availability (see table 4). Since beef manure is not usually incorporated, we’re going to assume that the manure is being broadcasted without incorporation and we’ve lost all of our ammonium nitrogen to volatilization (into the air).

1.4 pounds Ammonium N times 0% available (from table 4) equals 0 N available from ammonium

Table 4. Fraction of ammonium nitrogen available this year.
Sidedress Application
Injected 0.95
Sprinkler Irrigated 0.80 (if >0.4” applied) or 0.40 (if ≤0.4” applied)
Preplant Application and Not Incorporated
Surface – spring or fall 0
Preplant Application and Incorporated
SolidLiquid Applied When Air Temp > 50˚FLiquid Applied When Air Temp ≤50˚F
Immediately 0.95 0.95 0.95
One day later 0.5 0.7 0.7
Two days later 0.25 0.45 0.55
Three days later 0.15 0.25 0.45
Seven or more days later 0 0 0.25

So, using 84 cents/pound of N and manure with 9.5 pounds of nitrogen available per ton, our manure is worth about $8 per ton for the nitrogen alone.

$0.84 per pount of N times 9.5 pounds of N per ton equals $8 per ton

However, we know that manure contains many nutrients besides nitrogen, so we need to repeat this process for all nutrients and add them together. Without going through all the math for each nutrient, the sample of manure listed above is worth about $30.25 per ton – accounting for nitrogen (N), phosphorus (P), potassium (K), sulfur (S), and zinc (Zn).

Remember, we typically don’t apply just 1 ton per acre, so that makes manure a valuable part of our livestock and cropping operations.

This worksheet is a guide to the math for calculating nutrient availability and the price of those nutrients per ton.

Nutrient Needs

The last and most important factor in valuing manure is whether the crop you are growing needs the nutrients that will be applied with the manure. If the crop doesn’t need nutrients or the soil has sufficient nutrients for the crop, those nutrients are not as valuable. So, looking at the soil test and knowing what crop will be grown following the manure application will make a big difference in the value of the manure.

This article was reviewed by Javed Iqbal and Amy Schmidt.

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