Manure application equipment as well as irrigation equipment should be calibrated on a regular basis to determine accurate application rates. You should be able to accurately determine how many gallons, tons, cubic yards, or inches of manure or irrigation water you apply to a field.

Follow manufactures recommendation for calibration and/or refer to information on calibration of equipment given below and in the

Publications and Articles. Calibration worksheets are located in there and can be used to calibrate various manure application and irrigation equipment.

For an additional guidance, including video tutorials, on calibration of liquid and solid manure spreading equipment, click

HERE.

### Calibration of Manure Applicator/Spreader

An "application rate" - whether it is manure, fertilizer, or herbicide - is defined as the amount of material applied per unit area of land. For manure, it is usually expressed in tons per acre (solid or semi-solid) or gallons per acre (liquid, or slurry), as follows:

Application Rate = Amount Applied (tons, gallons) / Area covered (acres) So, to calibrate a manure spreader, you need to have reliable estimates of both amount applied and area covered. There are a number of different ways to estimate each parameter. Each of four methods is presented below.

**Method 1** - Based on Single Spreader Load: Solid, Semi-solid, or Liquid**Method 2** - Application Rate Based on Spreader Loads applied to a Field: Solid, Semi-solid, or Liquid**Method 3** - Application Rate Based on Plastic Sheet Subsample: Solid or Semi-solid**Method 4** - Average Application Rate Based on Storage Volume Applied to Fields- Adjustment to Obtain Desired Rate

#### Method 1. Based on Single Spreader Load: __Solid, Semi-solid, or Liquid__

**1. Estimate amount applied, or spreader capacity, based on one of following: **- Manufacturer's rated spreader capacity - For full liquid spreaders use rated capacity directly. Adjust to account for less than full capacity, for example, because of foaming or non-level surface. Actual load may typically be 90% of rated capacity. For box type solid or semi-solid spreader, adjust rated capacity according to fullness of load. Be sure to note if rated capacity is "heaped" or "struck (level) load". (Some equipment specifications include both.) If there is any uncertainty about the rated capacity, a more accurate method is to measure actual volume, as described below.
- Measured volume of spreader - Measure and calculate volume of spreader in cubic feet. Convert cubic feet to pounds, and then to tons or gallons, based on manure density. (See Manure Conversions)

*Note*: Manure density (weight per cubic foot) varies with moisture content, primarily depending on amount of bedding. For a more accurate estimate, weigh a five-gallon pail of manure, then multiply the weight by 1.5 to get the density in pounds per cubic foot.

Weigh spread load directly - If you have access to scales, weigh spreader full, then subtract spreader weight empty to get weight of manure. Convert to tons or gallons.

**2. Estimate area covered by one spreader load by doing the following: **- Measure width of one spreader pass, allowing for any overlap with adjacent passes.
- Measure distance traveled to empty spreader (adjusting for distance at beginning and end when spreading a partial rate) by one of the following:
- Use measuring wheel or long tape measure
- Measure number of tractor tire revolutions:
- Tie cord around rear tire at top.
- Measure distance traveled in exactly one revolution.
- Count number of tire revolutions to empty spreader.
- Distance = Number of revolutions x distance per revolution

- Calculate area covered by one spreader load:

Spreader width (ft) x Distance (ft)/43,560 sq ft = Area (acres)

**3. Calculate manure application rate by dividing amount applied by area covered: ****Application Rate = Amount Applied (tons, gallons) / Area covered (acres) **

__Manure Conversions:__

1 ton = 2000 pounds

1 cubic foot = 7.5 gallons

1 bushel = 1.25 cubic feet

1 gallon = 8.3 pounds

1 cubic foot = 62 pounds (wet) to 55 pounds (dry)