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Cost analysis: Rock fertilizer vs. poultry litter

William ‘Terry’ Halleran for Progressive Forage Published on 30 October 2017
Corn plant

I have often wondered, and have been asked several times, about the dollar value of poultry litter products as they relate to the cost of traditional rock fertilizers. I myself have used poultry litter in the past, with mixed results.

Please keep in mind the following bits of information:

1. Poultry litter is not often tested for analysis, so guaranteed percentages of nitrogen, phosphorus and potassium are not readily available.

2. Poultry litter is not consistent, as it may or may not contain more filler than manure at any given time. (Ask the provider if this is a decrusting or a total clean-out of the house.)

3. Availability and delivery of poultry litter is based on the time of year and house clean-outs.

4. Some litter is composted while others may come straight out of the barn, which, at times, may cause a few problems. Composted is better.

5. Understand there may be a few additional benefits to applications of poultry litter other than fertility, such as increased microorganism action and an improved carbon ratio.

Let us assume, for mathematical comparison purposes, the test analysis results for poultry litter would be 35-35-35 per ton. (If one wishes to dispute this point, then ask for a test.

Remember, the test will only be for the load at hand, as litter is not usually consistent.) Using the suggested application rate of 2 tons per acre litter (70-70-70), what would be the breakeven point if you were to choose traditional rock fertilizer over litter?

Fertilizer prices were obtained through local fertilizer dealers this spring and were used to calculate the values in Table 1.

Local fertilizer dealers provided prices

Working to solve the phosphorus level first (as DAP also carries nitrogen), the following was determined: 70 pounds / 0.46 = 152.17 pounds of DAP will meet the need. This also provides 27.39 pounds of nitrogen (152.17 x 0.18 = 27.39), which can be subtracted from the nitrogen yet needed.

Then 70 pounds of nitrogen needed minus 27.39 pounds already applied through DAP leaves 42.61 pounds yet to be obtained.

Working to solve the additional nitrogen requirement, using ammonium sulfate as our source, the following was calculated (this also adds additional amounts of sulfur to your soil as well; urea [treated], as the nitrogen source, might make it cheaper but no sulfur would be added): 42.61 pounds / 0.21 = 202.9 pounds of ammonium sulfate added to the mix. Both nitrogen and phosphorus are now met.

Last is the potassium element. Potash will be used to round out the blend: 70 pounds / 0.60 = 116.66 pounds of potash will be needed to complete the comparison. Furthermore, the costs of these items are listed in Table 2.

Potassium elements

Another area of concern may be tons delivered per load. In a rock fertilizer blend, each element is weighed to complete the mix matching your soil test recommendation.

After all, when you receive a load of corn or price your hay at “X” amount per ton, you usually weigh the load. If you purchase a load of poultry litter, you might want to ask for a weigh stub. A little extra is to your advantage, but less is not. Without a test analysis or a weigh ticket, you are only guessing at the load.

At this rate, 2 tons of poultry litter delivered and spread per acre should be equal to $91.89 of rock fertilizer. Anything higher than this is more than the cost of rock. So, are the additional benefits discussed earlier worth it?

Yes, poultry litter has definite advantages at times – just make sure you are getting what you pay for.  end mark

PHOTO: Image licensed through Thinkstock.

William ‘Terry’ Halleran is the agronomy specialist – Hickory County with the University of Missouri. Email william 'Terry' Halleran.

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