Calibrating application equipment

Equipment calibration is necessary to ensure manure and wastewater applications are made at desired rates.

Solid Manure Spreaders:

  • Weigh the loaded spreader, then divide this weight by the spreader volume (spreader length x spreader width x spreader height). If access to scales is available, some percentage of the loads can be weighed (for example, one or two of every 10 loads) and all loads assumed equal to the average of the weighed loads. However, scales are usually not available on-site, and another means of obtaining bulk density is needed.
  • An alternate method of obtaining bulk density involves weighing a known manure volume then using this information with volumetric spreader capacity to obtain spreader capacity in tons. A five-gallon bucket is a convenient known volume (2/3 ft3) to use for this measurement.
 
  1. Measure spreader length ft. x width ft. x height ft = spreader cubic feet (ft3).
  2. A five-gallon bucket equals 2/3 ft3.
  3. Weigh an empty 5-gallon bucket and write the weight down.
  4. Fill the bucket with manure. Do not compact the manure any more than might occur in the spreader.
  5. Weigh the full bucket and subtract the empty bucket weight. The result is the manure weight.
  6. The manure weight in lbs. ÷ 2/3 ft3 = manure lbs/ft3
  7. Take the manure lbs/ft3 x spreader ft3 = lbs. manure in spreader.
  8. Take lbs. manure ÷ 2000 lbs/ton = tons manure in speader.
  9. Repeat this procedure several times. Sample the manure at different places. Average the values to obtain a representative composite of the manure.
  10. The pounds of nutrients per load of manure are then found by multiplying the tons of manure per load by the pounds of nutrients per ton (from a laboratory analysis).

Liquid/slurry Manure Spreaders:

  • To calibrate liquid/slurry spreaders, first determine the volume of material in gallons from manufacturer specifications, or by taking the length x width x height of the spreader x 7.5 gal/ft3.
  • For the volume in cylindrical tanks multiply length x diameter x diameter x 0.8 x 7.5 gal/ft3. (0.8 represents 80% of load capacity).

Determining application rate:

Spreader: _____________________ Date:__________________
1. Load weight in tons (or volume in gallons): ____________
2. Distance traveled to spread one load (ft) ____________
3. Width of spread (ft) ____________
4. Area of spread (multiply line 2 x line 3) ____________ sq ft
5. Acres covered (divide line 4 by 43,560) ____________ acres
6. Application rate (tons/acre or gal/acre) (divide line 1 by line 5) ____________

*Note: you can also divide the pounds of nutrients per load by line 5 to get pounds of nutrients per acre.

 

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