Information presented in manufacturer's charts are based on average operat­ ing conditions for relatively new equipment. Discharge rates and application rates change over time as equipment gets older and components wear. For pump and haul application equipment, application rates and patterns may vary depending on forward travel and/or PTO speed, gear box settings, gate openings, operating pressures, spread widths, and overlaps.

Equipment should be calibrated on a regular basis to ensure proper appli­ cation rates and uniformity. Calibration is a simple procedure involving col­ lecting and measuring the material being applied at several locations in the application area. Calibration helps ensure that nutrients from animal waste are applied efficiently and at proper rates.

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Liquid applicators and tank spreaders are an alterna­tive to irrigation systems for transporting and apply­ ing liquid lagoon effluent, liquid manure slurries, and lagoon sludges. Proper location and design of pump­ ing and loading pads are necessary to protect equip­ ment and operators and avoid damaging the lagoon dike or embankment. Care should be taken to minimize spills during loading and transport.

Semi-solid (slurry) applicators can be calibrated by one of two methods: load-area method, and weight­ area method (see AG-553-4). Liquid applicators are best calibrated by the load-area method.

To use the load-area method, you must know the spreader capacity. Spreader capacity is normally rated by the manufacturer and often is indicated on the application equipment. Liquid spreaders are normally rated in gallons while semi-solid spreaders are rated in either bushels or cubic feet.

As the name implies, the load-area method involves applying a full load to a measured area. For ease of measurement, it is best to use a rectangular field pattern. For PTO-driven spreaders, application rate is dependent on ground speed so a uniform speed must be maintained throughout the swath length. Ground-driven applicators apply reasonably uniform rates independent of ground speed.

1. Spread at least one full load of manure in a rectangular field pattern.
2. Measure the length and width of coverage. Do not include the outer fringe areas of the coverage which receive much lighter applications than the overlapped areas.
3. Multiply the length (feet) by the width (feet) and divide by 43,560 to determine the coverage area in acres.
4. Divide the weight or volume of load of manure in the spreader by the acres covered to determine the application rate in tons or gallons per acre.
5. If the application rate (Item 4) is not acceptable, repeat the procedure at different spreader settings, speeds, or both until the desired application rate (tons or gallons per acre) is achieved.

1. Determine the capacity of the manure spreader.

   1. __________ gallons

2. Spread at least one full load using the regular spreading patterns of the applicator.

   2. Forward speed, gear, or throttle setting

      Trial 1	Trial 3	Trial 3

   3. PTO speed or setting

      Trial 1	Trial 3	Trial 3

   4. Spreader gate setting

      Trial 1	Trial 3	Trial 3

3. Measure the area of spread.

   5. Spread area width

      Trial 1	Trial 3	Trial 3
      ft	ft	ft

   6. Spread area length

      Trial 1	Trial 3	Trial 3
      ft	ft	ft

   7. Spread area (e × f)

      Trial 1	Trial 3	Trial 3
      ft2	ft2	ft2

   8. Spread area (g + 43,560)

      Trial 1	Trial 3	Trial 3
      acre	acre	acre

4. Compute the manure application rate:
   9. Number of loads spread

      Trial 1	Trial 3	Trial 3

   10. Capacity per load (a)

       Trial 1	Trial 3	Trial 3
       gallons	gallons	gallons

   11. Total manure spread (i × j)

       Trial 1	Trial 3	Trial 3
       gallons	gallons	gallons

   12. Application rate (k + h)

       Trial 1	Trial 3	Trial 3
       gal/acre	gal/acre	gal/acre

5. Compute the nutrient application rate:
   13. Manure analysis

       Nutrient	Trial 1	Trial 3	Trial 3
       N	lbs/1000 gallons	lbs/1000 gallons	lbs/1000 gallons
       P2O5	lbs/1000 gallons	lbs/1000 gallons	lbs/1000 gallons
       K2O	lbs/1000 gallons	lbs/1000 gallons	lbs/1000 gallons

   14. Application rate (I × manure analysis number + 1000)

       Nutrient	Trial 1	Trial 3	Trial 3
       N	lbs/acre	lbs/acre	lbs/acre
       P2O5	lbs/acre	lbs/acre	lbs/acre
       K2O	lbs/acre	lbs/acre	lbs/acre

6. If the application rate is not acceptable, repeat the procedure at different spreader settings, speeds (Item 2), or both, until the desired application rate is achieved.

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