5.1 Manure Application Rate / Record Keeping Worksheet

Calculating the correct rate of manure to apply is important to prevent the buildup of excess nitrogen or phosphorus in the soil and contamination of ground and surface waters. Follow the directions below to calculate application rates of manure based on nitrogen or phosphorus.

You will need the following information:

Soil and Manure test results:

Follow the directions of Step 4 to obtain this information.

The Nutrient Availability Factor

Nutrients are released as manure decomposes in the soil. The nutrient availability of your soil is based upon what kind of manure you are applying, and is calculated for the year of application. Use Table 4 - Estimate of Available Nitrogen to determine this number.

Use the following Worksheet (Manure Application Rate), which considers soil and manure nutrient content as well as the kind of manure you are applying to estimate manure application rates.

Word Excel

(*Note- Excel spreadsheets are programed to do calculations for you. On some computers you can do calculations directly on your computer. On others you must save Excel files to your computer or disk before using the spreadsheets. )

Directions for Manure Application Worksheet:

If soil test phosphorus levels are below 50 parts per million (ppm) calculate manure application rates based on nitrogen (N) or phosphorus (P2O5) recommendations, or N or P2O5 removal by the crop. Between 50 and 100 ppm soil test phosphorus, calculate application rates based on crop P2O5 removal. No further applications of manure are recommended when soil test phosphorus levels are above 100 ppm.

1. Nutrients needed (lbs/ acre)

These are based on your soil report recommendation and on the crop to be grown and average yield. Refer to the table of common crop uptake values, or use fertilizer guides, or contact your county Cooperative Extension agent or NRCS office for this information.

2. Nutrients from other sources (credits) (lbs / acre)

These may include residual nitrate-N from soil tests, supplemental fertilizers, N in irrigation water, previous legume crop credits, or nutrients from previous manure applications.

3. Additional nutrients needed

The Excel spreadsheet will subtract line 2 from line 1.

4. Total N and P2O5 in manure

Enter the total N and P2O5 in manure from you manure test report. Total N and P2O5 in manure (on a fresh weight or as-sampled basis) is based on a recent manure report or book estimate for your manure type. If you do not have a recent manure test contact your local Extension or NRCS office for more information.

5. Nutrient Availability Factor

Enter the nutrient availability factor on line 5. Nutrients, particularly nitrogen, are released over time as manure decomposes in soil. The nutrient availability factor is the fraction of total N or P2O5 in manure available in the year of application. See Table 4 - Estimate of Available Nitrogen for more information.

6. Available nutrients in manure

The Excel spreadsheet will multiply line 4 by line 5.

7. Manure Application Rate

The Excel spreadsheet will divide line 3 by line 6. This will give you your manure application rate.

Back to Step 5