D A I R Y I n i t i a t i v e s N E W S L E T T E R
V o l u m e 1 0 I s s u e 2 S u m m e r 2 0 0 1

Managing Manure for Fun and Profit

Okay, "fun" might be stretching it. But good manure management truly will help your operation become more profitable.

PHIL NESSE
University of Minnesota Extension Service, Central Lakes Agricultural Center, Staples

Looking for money? Try looking in your manure pile. Many dairy producers can boost their economic return by improving manure and nutrient management through the following five-step plan:

1. Test Your Soil

Soil testing can tell you which fields should receive manure. It's especially important on fields that have received heavy manure applications in the past. Test soils for pH, phosphorus (P), potassium (K), and where appropriate, nitrate-nitrogen. In western Minnesota, use the fall nitrate test. Elsewhere in Minnesota, the spring nitrate test is a relatively new option. Check with your county Extension educator to find out if this test is recommended for your county.

Nitrate-nitrogen testing is not recommended for use in sandy soils.

2. Test Your Manure

Test manure for total nitrogen, P, K, and perhaps ammonium-nitrogen.

For pit manure, agitate before sampling, then take several subsamples as the pit is being emptied. Keep the manure cool. Mix the samples and pour into the container provided by the laboratory. (Only fill the container about 3/4 full to allow for gas expansion.) Solid manure should also be a composite of several subsamples.

Freeze the sample and hand deliver or mail to the laboratory early in the week.

Sample manure yearly for several years until a consistent result becomes clear. Then sample it whenever changes occur in your operation that may affect the manure test.

For more information see Livestock Manure Sampling and Testing (FO-6423-C), available from your local Extension office or from the University of Minnesota Extension Service Distribution Center at 800/876-8636.

3. Calibrate Your Spreader

To calibrate a liquid manure spreader, assume that about 90 percent of the listed capacity is applied each time the spreader is emptied. Spread a load to see how many acres you cover. Then divide the gallons applied by the number of acres to get the application rate at that spreading speed.

Calibration of solid manure spreaders is more difficult. Simply using the spreader capacity to estimate application rate is often misleading. Contact your Extension office or the Natural Resource Conservation Service (NRCS) for help weighing a representative load of manure using load cells. Once you know the weight of a load, you can divide the weighed manure (in tons) by the area (in acres) that received one load to get application rate in tons per acre at that spreading speed.

4. Determine Nutrient Needs

What application rate should you use? That depends on past manure applications, legume plowdowns, crop to be grown, yield goal, soil organic matter, and in a few cases, soil texture. It also depends on the source of manure (livestock type), method of incorporation, and time of application.

Nitrogen is the nutrient that is most likely to limit crop growth. Although some situations near surface water require attention to phosphorus, the new feedlot rules generally allow producers to apply manure based on nitrogen needs of the crop.

Unless you are a producer in the western part of the state who uses the fall nitrate test, use this process to determine how much manure to apply:

Find the nitrogen recommendation for the crop you are planning from University of Minnesota fertilizer recommendation tables (available from your Extension office).
Subtract 25 percent of the nitrogen applied from manure prior to last year's crop from the N recommendation.
Divide the remainder by 55 percent (0.55) if manure will be immediately incorporated, by 25 percent (0.25) if there will be no incorporation.
Divide by the nutrient content of the manure.

5. Plan and Keep Records

Minnesota Pollution Control Agency (MPCA) feedlot rules require record keeping for operations with more than 100 animal units and require manure plans for certain situations. However, planning and record keeping are important parts of any good manure management program.

For information on manure management planning, see Developing a Manure Management Plan (BU-6957-D, 2001), available from the University of Minnesota Extension Service Distribution Center at 800/876-8636. For information on MPCA rules, call MPCA at 800/657-3864 or 877/333-3508 and ask for Land Application of Manure: Minimum State Requirements.

The Minnesota Department of Agriculture has a list of laboratories certified for manure analysis available on-line (or from your county Extension Office).

Test Manure for Nutrient Content

If you are depending on industry average table information to estimate nutrient values in manure, you may be "shooting in the dark"!

The importance of manure testing is apparent from a study conducted in 1994 and 1995 by the Wadena SWCD, the Wadena County Natural Resource Conservation Service, and the University of Minnesota Extension Service. The study showed substantial variation in nutrient content of manure. Tests of 35 Wadena County earthen dairy manure pits showed a range per 1,000 gallons of 8 to 42 pounds of N, 2 to 19 pounds of P, and 5 to 45 pounds of K. In 8 facilities with solid manure, samples showed a range of 9 to 13 pounds of N, 5 to 6 pounds of P, and 8 to 12 pounds of K per ton of manure.

These results suggest that many if not most farmers who base their rates on the table values are either overapplying or underapplying manure. Overapplication can reduce farm profitability. It can also cause pollution. Underapplication can lead to reduced yield or added reliance on costly commercial fertilizers.

The bottom line? Table values aren't good enough. Dairy manure should be sampled and sent to a laboratory for nutrient analysis.

TIP: If you don't have enough acreage within several miles of your manure storage facility, try arranging for a neighboring crop farmer to take some of your manure.

To Conserve Nutrients, Apply Manure Later

To maximize nutrient value to the crop, apply manure after mid-October or before seeding in spring.

When soil temperatures exceed 50¡ F, nitrogen in ammonium form readily converts to nitrate-nitrogen, which is prone to leaching. As a result, as much as one third of total nitrogen can be lost through late summer or early fall application. Under typical conditions, that could mean a loss of up to $12 worth of nitrogen per acre.

Beyond Feedlot Rules

There are many ways to improve manure management. Only some of these practices--most notably, use of land-grant nutrient recommendations, manure testing for feedlots with more than 100 animal units, and phosphorus soil testing for feedlots with more than 300 animal units--made it into the MPCA's recent feedlot revisions. Practices such as soil testing, manure testing, use of proper recommendations, and application of manure at the right time and rate will put more money into the pocket of many producers.

For more information related to manure management, contact your county
Extension office or Soil and Water Conservation District (SWCD) office.