Many of you have adjusted your attitude about hog manure. You view it as a resource instead of a waste product.

Today you have a better understanding of its value as a substitute for commercial fertilizer. You also understand the public consequences of not handling manure correctly when you apply it to the land.

A critical step in that process is calibrating your equipment. You should do this at least annually, more often if you have made production changes in your operation.

Rick Koelsch, University of Nebraska livestock environmental engineer offers two step-by-step methods to help you calibrate equipment for liquid and for solid manure application.

Remember, incorporating manure into the soil immediately upon surface spreading is the environmentally responsible thing to do. It makes for good relations with neighbors. 

When you know the manure spreader’s capacity or its weight, the following calibration checklist provides a sound guide. Koelsch says this method works with a liquid manure spreader filled to capacity.

A. Fill the spreader to its capacity or weigh the spreader.

B. Measure the width of one spreader pass. Avoid measurements near the beginning or end of the spread pattern where the machine may not be operating at capacity. Allow for typical overlap of adjacent passes.

C. Tie a rope around the tread of a tractor tire to mark it.

D. As you spread, measure the distance you’ve traveled by one full revolution of the tire using the rope as a reference.

Distance≈revolution =          feet

E. Again using the rope as a reference point, count the number of tire revolutions required to empty the spreader.

Distance traveled =

Distance≈revolution x revolutions =            feet

F. Use the following formula to calculate the application rate:

Gallons per acre =

tank volume (gallons) x 43,560 ≈ distance traveled x width

(43,560 is a factor for converting square feet to acres.)

Tons per acre = spreader net weight (pounds) x 22 ≈ distance x width

(22 is a factor supplied by the university for converting pounds to tons and square feet to acres.)

You can estimate solid and semisolid manure application rates by collecting manure on a plastic sheet and then measuring it. For manure spreaders where true capacity is difficult to estimate, this method provides the most accurate answer, says Koelsch.

A. Cut three equal-size sheets of heavy-duty plastic. For example, if a sheet measures 22 square feet (48 inches by 66 inches or 36 inches by 88 inches), the manure weight in pounds that you will eventually measure will equal the application rate in tons per acre.

B. Weigh a bushel basket plus one plastic sheet on a platform scale.

C. Lay the sheets down flat in a field, securing the corners. Space the three  sheets near the beginning, middle and end of an area that you will spread with one manure spreader load.

D. Drive your tractor at your typical speed over the sheets. Start the spreader early enough so that the first sheets collect a representative sample.

E. Check yourself. Did the sheets remain flat and collect a representative sample? If not, repeat steps C and D.

F. Carefully fold the individual sheets without losing manure and place each sheet in a separate bushel basket.

G. Weigh the basket, plastic and manure. Subtract the empty weight of the plastic sheet and bushel basket from the total weight to come up with the net weight of the manure.

H. Compute the application rate using the following formula:

Tons per acre = Pounds of manure x 22 ≈ Area of sheet (square feet)

I. Repeat steps F through H for each sheet.Compute the average application rate by adding the application rates of the three samples and dividing by three.

If you try these equations and still need further assistance to calibrate your manure application equipment, contact the equipment dealer, an agricultural engineer or local extension agent.

Remember this is just one step. You also need to conduct manure and soil tests and take into consideration nutrient intake of past and future crops.