Environmental Engineering Reference
In-Depth Information
3. Fill the spreader with the material you wish to apply (fertilizer, seed,
etc.). Fill the hopper only to the level you will use when the material
is actually applied.
4. Make several short trial runs over the area and practise opening and
closing the spreader. Do so gradually, not in a fast, jerky way. Make
sure the material drops from the full length of the opening.
5. Determine the weight of the fertilizer applied by the spreader over a
known area: some, but not all, commercial spreaders come equipped
with an attachable catch pan that fits under the spreader opening.
When no catch pan is available, this calibration requires two people:
one to hold the spreader and squeeze the opening lever and the other
to lift one wheel and turn it manually. While the first person holds the
lever in the open position, the other should turn the wheel ten times.
Collect the fertilizer that drops from the spreader opening on a large
piece of paper and weigh it.
6.
If the amount you collect in the catch pan is less than that intended,
increase the gate opening. If it is more, reduce the opening. Repeat
this procedure until the amount dropped is within 10% of the desired
amount (110-130 g, if the intended amount is 120 g). After reaching
this final setting, repeat the procedure at least one more time to be
sure that the calibration is correct.
The same calibration procedure is used for fertilizer, seeds, granular
pesticides or any material to be applied, but remember that the rate of
application depends on the physical properties of the material, so the
same settings cannot be used for different materials.
Calibrating a Rotary Spreader
Follow these steps in order to calibrate a rotary spreader (Fig. A.2):
1. Check the spreader to make certain all parts are operating properly.
Then follow steps 2 and 3 to determine the 'effective' width of application.
2. Fill the hopper about half full with the material you plan to apply and
set the spreader on 'medium', i.e. about half open. Run the spreader
over bare ground or a hard surface, where the width of the surface
covered by the spread material can be measured.
3. The amount of material applied by a rotary spreader (Fig. A.2) is not
constant across the entire width of application. More material is
applied towards the centre and less at the edges. If the full applica-
tion width is 5 m, only about the central 3 m receives an approxi-
mately even application. The outer 1 m on each edge receives much
less. The central area is called the effective width of application, and
it (not the full width) is used in all calculations.
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