Manure Composting Quick Guide

Source: On-Farm Composting Handbook, NRAES-54 (Rynk et al., 1992)

More information on these characteristics can be found in publication NM1478
(Keena, 2022)

Use the table below to add carbon-rich materials to raise C:N

Pounds of bulk material needed to raise C:N to 30:1 (per 100 lb. of manure)

Example: If the manure has a C:N of 15:1, you will need to add 190 pounds of oat straw per 100 pounds of manure to bring the overall C:N up to the desired 30:1.

Source: On-Farm Composting Handbook, NRAES-54 (Rynk et al., 1992)

Use the table below to add nitrogen-rich materials to lower the C:N

Pounds of bulk material needed to raise C:N to 30:1 (per 100 lb. of manure)

Example: If the manure has a C:N of 40:1, you will need to add 35 pounds of grass clippings per 100 pounds of manure to bring the overall C:N down to the desired 30:1.

Source: On-Farm Composting Handbook, NRAES-54 (Rynk et al., 1992)

More details can be found in publication NM1418 Manure Spreader Calibration For Nutrient Management Planning (Keena, 2021)

Weight Method

Step 1

Pounds applied =
Weight of full spreader –
Weight of empty spreader

Step 2

Area applied =
Length of spread area (ft) x
Width of spread area (ft)

Step 3

Tons per acre =

[Pounds applied (step 1)]

[Area applied (step 2)]

x 21.8

Tarp Method

Step 1

Pounds applied =
Weight of full tarp and bucket – Weight of empty tarp & bucket

Step 2

Area of tarp =
Length of tarp (ft) x
Width of tarp (ft)

Step 3

Tons per acre =

[Pounds applied (step 1)]

[Area of tarp (step 2)]

x 21.8

Where does 21.8 come from?

To convert pounds per square feet to tons per acre, we need to multiply the weight in pounds by 43,560 square feet (= 1 acre) and divide that by 2,000 pounds (= 1 ton). To simplify this, we multiply by 21.8, which is 43,560/2,000.

Step 1

Determine P needs of the crop

Crop P needs = Expected yield x Crop P2O5 removal

Step 2

Determine Plant Available P (PAP) content of the compost

If the compost analysis reports phosphorus as “P”,
you can convert it to P2O5 by multiplying by 2.29

80% of total P is plant available

PAP = Total P2O5 content of compost (from compost analysis) x 0.80

Step 3

Calculate application rate

Application rate (in tons per acre) = Crop P needs (step 1) ÷ PAP (step 2)

Crop P Removal Rates

How much plant-available N has been applied?

10-15% of total N in compost is available the first year
(use 0.10 for cattle & lower-N compost, and 0.15 for poultry & higher-N compost)

Plant-available N =
Total N content of compost (from compost analysis) x .10 x application rate

Keena, M. A. 2022. Composting Animal Manures: A guide to the process and management of animal manure compost. North Dakota State University Cooperative Extension publication NM1478.

Keena, M. A. 2021. Manure Spreader Calibration for Nutrient Management Planning. North Dakota State University Cooperative Extension publication NM1478.

Rynk, R., M. van de Kamp, G. B. Willson, M. E. Singley, T. L. Richard, J. J. Kolega, Gouin, F. R., L. Laliberty, D. Kay, D. W. Murphy, H. A. J. Hoitink, W. F. Brinton. 1992. On-Farm Composting Handbook (NRAES 54). Northeast Regional Agricultural Engineering Service. Ithaca, New York.

Thank you to our reviewers: Lindy Berg, NDSU Extension, Towner County; Renae Gress, NDSU Extension, Morton County; Greg Klinger, UMN Extension, Water Resources Center; and Annie Klodd, UMN Extension, Farmington Regional Office

More information is available at ndsu.edu/agriculture/ag-hub.

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