Section 13 – Manure Application Rates

This section will help you calculate the amount of manure to apply to your fields in order to utilize the nitrogen and phosphorus as crop nutrients.

To complete this section, you will need:
• Manure test reports

• Soil test reports for the fields receiving manure

• Manure test reports and manure application rates for the previous two years if applicable and available.

• List of crops to be grown and yield goals

• Nitrogen and phosphorus fertilizer recommendations corresponding to those crops, yield goals, and soil tests. Find this information in NDSU Extension publication SF-882, which can be found at: http://www.ext.nodak.edu/extpubs/plantsci/soilfert/sf882w.htm

• Worksheets 1, 2, and 3 from NDSU Extension publication
AE-1187, Manure Application Planning Workbook which can be found at:
http://www.ext.nodak.edu/extpubs/ansci/waste/ae1187-1.pdf
http://www.ext.nodak.edu/extpubs/ansci/waste/ae1187-2.pdf
http://www.ext.nodak.edu/extpubs/ansci/waste/ae1187-3.pdf

Copy each of the four worksheets so they can be filled out. You will also need information from Tables 2 and 3 in AE-1187.

Detailed instructions:

Worksheet 1. Previous manure applications and nitrogen credits.
Because much of the nitrogen in manure is in organic form, it is released
to plants over a period of time as the nitrogen mineralizes. See Table 2
of AE-1187 for the percentage of manure nitrogen which is available to
plants in each of years 1, 2, and 3 after manure application. Note that it
varies with the species of animal and the type and time of incorporation.
Table 3 tells you that P2O5 is 80% available in Year 1 after application.

1) Column 1 – enter the N analysis of manure applied to the field last year if any.
2) Column 2 – enter the application rate of any manure applied last year.
3) Column 3 – enter the percent of applied N available in Year 2 from Table 2.
4) Column 4 – multiply column 1 x column 2 x column 3 to find the amount of manure N applied last year which will be available to this year’s crop.
5) Columns 5 through 8 – repeat the above procedure for manure applied to the same field two years ago.
6) Add the manure credits for the past two years (columns 4 and 8) to get the total N which will be available from previous manure applications.

Worksheet 2. Fertilizer recommendations and crop requirements.

1) Columns 1 and 2 - enter the crop and yield goal.
2) Column 3 – enter the nitrogen requirement for that yield goal from SF-882.
3) Column 4 – enter the soil test nitrate nitrogen from the soil test report.
4) Columns 5 & 6 – enter the appropriate N adjustments if they are not already included in the soil test report.
5) Column 7 – enter the previous manure application N credit calculated on Worksheet 1, column 9.
6) Column 8 – enter the net fertilizer N requirement by subtracting Columns 4, 5, 6, and 7 from the N requirement in column 3.
7) Column 9 – enter the P2O5 fertilizer requirement from SF-882.

Worksheet 3. Determining the manure application rate.

1) Columns 1 and 2 – enter the N and P2O5 requirements from Worksheet 2, Columns 8 and 9 respectively.
2) Columns 4 and 5 – enter the manure test analysis for total N and P2O5, respectively.
3) Column 7 – enter the percent of manure N available to the crop for the first first year after application found in Table 2, noting the species of animals and the time and type of incorporation.
4) Column 8 – enter the percent of manure P2O5 available to the crop from Table 8 which is 80%.
5) Column 10 – multiply the manure N analysis in column 4 by the percent available in column 7 and enter the available N content of the manure.
6) Column 11 – multiply the manure P2O5 analysis in column 5 by the percent available in column 8 and enter the available P2O5 content of the manure.
7) Column 13 – Divide the N requirement of the crop listed in column 1 by the available N content of the manure in column 10. This is the tons per acre or 1000 gallons per acre which needs to be applied to meet the N requirements of the crop.
8) Column 14 – Divide the P2O5 requirement of the crop listed in column 2 by the available P2O5 content of the manure in column 11. This is the tons per acre or 1000 gallons per acre which needs to be applied to meet the P2O5 requirements of the crop. Typically, this will be one-fourth to one-half of the N requirement calculated above.