**TECHNICAL NOTES**

**USDA-Natural Resources Conservation Service**

**Boise, Idaho**

TN AGRONOMY NO. 27 September 1990

Prepared by Floyd G. Bailey, State Conservation Agronomist and Janice L.
Jinings, Area Agronomist, Boise, Idaho from information contained in
EPA's document, "Manure Management for Environmental Protection."

MANURE SPREADER CALIBRATION

HOW TO CALIBRATE MANURE SPREADERS

Spreading manure on cropland is an excellent way to use farm produced
manure. Nutrients contained in manure can be used to supply growing
crops with nitrogen, phosphate and other nutrients.

Proper spreading helps make better use of nutrients in manure. It can
also help maintain surface and ground water quality by applying the
amounts of manure that can best be used by plants.

[Manure Application Rates]{.underline}

Manure application rates should be based on crop needs, existing soil
nutrient levels and the nutrients in the manure to be spread. Soil
tests, manure analysis and crop fertilizer guides can provide this
information.

Excess manure application wastes nutrients, and increases potential for
groundwater contamination. Knowing the amount of manure the spreader is
applying is essential to proper use of manures. Manure spreaders can be
calibrated using the following processes.

[Calibrating solid or semisolid manure spreaders.]{.underline}

The items needed are:

-   A plastic sheet (6 ft. x 6 ft. or 10 ft. x 10 ft. is good, but any
    size will do)

-   A scale (milk or bathroom scale)

-   A bucket

1\. Weigh the sheet with the bucket on the scale.

2\. Lay the sheet in the field where manure will be spread. Place the
sheet far enough into the field to get enough distance to put the
spreader in gear and bring the tractor up to speed. Most spreaders apply
less at the beginning and at the end of the load.

3\. Drive the tractor and spreader directly over the sheet.

4\. Fold the sheet so that no manure is spilled. Put the sheet in the
bucket and weigh both on the scale.

5\. Subtract the weight of the empty bucket and sheet (in step 1) from
the weight of the sheet and bucket filled with manure. This number is
the weight of the manure collected on the sheet.

6\. Repeat the procedure and determine an average for the two weights.

7\. From Table 1 (under the size of sheet and pounds of manure on
sheet), determine tons of manure applied per acre.

8\. If the size of the sheet used or the pounds of manure collected is
not on the chart, the following formula should be used to calculate tons
per acre.

[Pounds of manure x 21.8]{.underline} = tons of manure per acre

Size of sheet in square feet

(length x width)

TABLE 1. Manure Spreader Rate Calibration

Sheet Size

[Manure on sheet (lb) 6 ft. x 6 ft. 10 ft. x 10 ft.]{.underline}

tons manure/acre

5 3.0 1.1

6 3.6 1.3

7 4.2 1.5

8 4.8 1.7

9 5.4 2.0

10 6.1 2.2

11 6.7 2.4

12 7.3 2.6

13 7.9 2.8

14 8.5 3.1

15 9.1 3.3

16 9.7 3.5

17 10.3 3.7

18 10.9 3.9

19 11.5 4.1

20 12.1 4.4

21 12.7 4.6

22 13.3 4.8

23 13.9 5.0

24 14.5 5.2

25 15.1 5.4

26 15.7 5.7

27 16.3 5.9

28 16.9 6.1

29 17.5 6.3

30 18.2 6.5

31 18.8 6.8

32 19.4 7.0

33 20.0 7.2

34 20.6 7.4

35 21.2 7.6

TABLE 2. Manure Spreader Capacity

[Spreader Size]{.underline} [Tons of Manure]{.underline}

[In gallons^1^]{.underline}

1000 4

2000 8

4000 16

[In bushels^2^]{.underline}

75 2.8

100 3.75

125 4.7

150 5.6

[In cubic feet^3^]{.underline}

100 3

200 6

300 9

[\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_]{.underline}

^1^ 1 gallon manure = 8 pounds

^2^ 1bushel manure = 75 pounds

^3^ 1 cubic foot manure = 60 pounds

[Calibration of Liquid Manure Spreader]{.underline}

The items needed are a yardstick or tape measure and a string or rope.

1\. Determine the manure spreader's capacity in tons or gallons using
Table 2.

2\. Tie the string around the tractor tire at the top of the tire. Mark
the ground directly below the string where the tire rests on the ground.
Pull the tractor forward until the string is again at the top of the
tire (one revolution). Mark the ground again, as before. Using the tape,
measure the distance between the two marks made on the ground. This is
the distance the tractor moved with one revolution of the tire.

3\. Spread the load, counting the number of times the rope comes to the
top of the tire. Multiply the number of revolutions the tire made to
spread the load by the number of feet the tractor moved in one
revolution (step 2). This is the distance traveled to spread the load.

4\. Measure the width (in feet) that the spreader is covering with
manure.

5\. Multiply the distance traveled to spread the load (step 3) by the
width the spreader is covering with manure (step 4). Divide that number
by 43,560 (the square feet in one acre). This is the number of acres
covered.

6\. Divide gallons or tons of manure applied (the spreader capacity
found in step 1) by the number of acres covered (step 5). The result is
the tons or gallons applied to that acreage.

Spreader capacity (step 1) = tons or gallons of manure applied per acre

Acres covered (step 5)

Once the rate being spread has been determined, adjustments in either
tractor speed or spreader output may have to be made. After any change
is made, the spreader should be recalibrated. It may take several tries
to get the proper adjustment to apply the desired rate. When several
passes are being made through the field, a small amount of the manure
being spread should overlap what is on the ground from the previous
pass. Too much overlap leads to over-application and too little gives a
low application rate and poor distribution of nutrients. The following
example and worksheet can be used to determine the application rate.

Worksheet for Calibrating Solid or Semisolid Manure Spreaders

[Example]{.underline} [Your farm]{.underline}

1\. Weight of empty bucket and sheet [\_\_\_\_\_\_\_]{.underline} lb.
[\_\_\_\_\_\_\_\_]{.underline} lb.

2\. Weight of bucket and sheet with manure [\_\_\_\_\_\_\_]{.underline}
lb. [\_\_\_\_\_\_\_\_\_]{.underline} lb.

3\. Weight of bucket, sheet and manure (step 2)

minus weight of bucket (step 1) [\_\_\_\_\_\_\_]{.underline} lb.
[\_\_\_\_\_\_\_\_\_]{.underline} lb.

4\. Tons applied per acre (from Table 1) [\_\_\_\_\_\_\_]{.underline}
lb. [\_\_\_\_\_\_\_\_\_]{.underline} lb.

\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*

5\. If the table in step 4 cannot be used because pounds [28 lb. x
21.8]{.underline} [xx lb. x 21.8]{.underline}

of manure on sheet or size of sheet are not listed, 36 sq. ft. xx sq.
ft.

multiply the pounds of manure on sheet by 21.8, then

divide that number by the size of the sheet used (in

square feet) = 16.9 tons/acre = xx tons/acre

Worksheet for Calibrating Liquid Manure Spreaders

[Example]{.underline} [Your farm]{.underline}

1\. Spreader capacity in tons or gallons [\_\_\_\_\_\_]{.underline} tons
[\_\_\_\_\_\_\_]{.underline} tons

[\_\_4000]{.underline} gallons [\_\_\_\_\_\_\_]{.underline} gallons

2\. Distance tractor tire covered in one revolution
[\_\_\_\_15]{.underline} ft. [\_\_\_\_\_\_\_]{.underline} ft.

3\. Number of tire revolutions to spread load [\_\_\_\_80]{.underline}
revolutions [\_\_\_\_\_\_\_]{.underline} revolutions

4\. Distance tractor tire covered in one revolution
[\_\_\_\_\_15]{.underline} ft [\_\_\_\_\_\_\_]{.underline} ft.\_

(step 2) multiplied by number of revolutions [\_\_x\_\_80]{.underline}
revolutions [\_\_\_\_\_\_\_]{.underline} revolutions

(step 3) [=\_\_1200]{.underline} ft. traveled
[\_\_\_\_\_\_\_]{.underline} ft. traveled

5\. Feet traveled to spread load (step 4) multiplied [1200ft x
15ft]{.underline} [\_\_ft x ft]{.underline}

by width manure is spread, divided by the 43,560 sqft/acre 43,560
sqft/acre

number of square feet in one acre = [\_\_\_\_0.4\_]{.underline} acres =
[\_\_\_\_\_\_\_\_\_]{.underline} acres

6\. Amount of manure applied (step 1) in gallons [\_\_4000]{.underline}
gallons [\_\_\_\_\_\_\_\_]{.underline} tons/gallons

or tons divided by acres in which it was

applied (step 5) [\_\_\_\_\_\_\_]{.underline} acres
[\_\_\_\_\_\_\_\_]{.underline} acres

7\. Quantity of manure applied per acre = [10,000 gal/acre]{.underline}
= [\_\_\_\_\_\_\_\_]{.underline} tons/gal/acre