STEP 7  Calibrating Your Spreader

Once you have determined how much manure you want to apply, manure spreader calibration is important. There are a number of methods for calibrating manure spreaders, including:

1. Weigh a load, and with normal application, measure the area it covers. This method tends to be the most practical for a producer. A relatively good estimate can be obtained by counting the number of loads per field coupled with the weights of each load (Davis, pers. comm. 2000).

2. Spread a meter-square tarp on the ground and spread solid manure as you would in the field. Weigh the tarp and the manure and find the equivalent in Table 9. Research conducted by Colorado State University found this method to be impractical for producers. Due to the density and quality of the manure, the coefficient of variation using the tarp method was as much as 30% (Davis pers.comm. 2000).

3. For liquid manure, use a straight walled pail on the ground. Spread the manure as you would in the field and then measure the depth of manure in the pail and find the appropriate application rate in Table 10.

Another important consideration is making sure the load is level, if there is more manure on one side of the truck, the spreading pattern is not even (Davis pers. comm. 2000). Spreading manure with beater spreaders can be highly variable. The application rate at the beginning and at the end of each load of manure may be lower than average but this can be compensated for by lapping the runs and by changing the direction of spreading from application to application in the same field. The key is to communicate with the load operator and request that all loads are filled to a similar volume (Gillund et. al 1999).

Table 9.  Calibration of Manure Spreaders for Solid Manure (Ontario Ministry of Agriculture, Food and Rural Affairs 1998)

Solid Manure Calibration
Using a 1 m x 1 m ( 40 in. x 40 in) tarp

Weight/sheet

Application rate

kg

lb

tonnes/ha

tons/ac

0.5

1

3.6

1.6

1

2

7.2

3.2

1.5

3

10.8

4.8

2

4

14.3

6.4

2.5

5

17.9

8.0

3

7

25.1

11.2

5

10

35.8

16.0

7.5

15

53.8

24.0

 

Table 10.  Calibration of Manure Spreaders for Liquid Manure (Ontario Ministry of Agriculture, Food and Rural Affairs 1998)

Liquid Manure Calibration
Using a straight walled pail

Depth of manure

Application rate

mm

L/ha

In

Gal/ac

2.5

25,000

1/10

2,265

3.1

31,000

1/8

2,825

6.3

63,000

5,650

9.4

94,000

3/8

8,500

12.5

125,000

11,325

15.6

156,000

5/8

14,150

18.8

188,000

17,000

25

250,000

1

22,650