Gason 7312, Operator'S Manual

Page: 29 / 110

Application Rate
– Ground Drive
Page 25
07/18
9. Weigh the sample collected and multiply the
answer by 20 if the full number of handle
turns for 1/20
th
of a hectare was used.
Fig.42. Weighing the sample.
10. Increase or reduce the rear door setting to
increase or reduce the application rate.
Example 1
Urea is to be spread at an application rate
of 80kg/ha. The bout width for this particular
product has been estimated at 20 metres. The
bulk density of the urea has been checked and
measures 0.76 tonnes/cubic metre. Using the
Rate Chart from the rear of the manual the
closest chart applicable using the lowest
gearbox ratio possible has been reproduced in
Fig. 43.
Fig.43 Rate Chart example.
The chart shows an estimated rear door
opening of 119mm. After setting the rear door to
this setting the jockey wheel was rotated to prime
the feed chain and discharge area. The collection
bag or trays were emptied and replaced ready for
the actual test. The jockey wheel was rotated 19.6
turns as per table 44 on page 26 for a 1/20
th
of a
hectare test at a 20 metre bout width.
The total sample was then weighed and
multiplied by 20 to obtain the application rate.
Eg. Sample weight 3.78kg x 20 = 75kg/ha.
The door setting could be opened by a
couple of millimetres to increase the rate to the
required 80 kg/ha.
Example 2
Lime with a bulk density of 1.09
tonnes/cubic metre is to be spread at a 10 metres
width at a rate of 1600kg/ha. The best gearbox
ratio that can be used for this product from the
Rate Chart is high ratio chart with a bulk density of
1.1 t/cubic m.
The chart suggests a door opening of
94mm. After priming, cleaning and replacing the
calibration trays or tarp, the jockey wheel was
rotated 1/10
th
of 39.1 turns because the
application rate was above 500kg/ha. This means
that instead of 39.1 turns, the wheel was rotated
3.9 turns. It also means that instead of multiplying
the sample weight from both trays by 20 it was
multiplied by 200 e.g. (10 x 20 =200).
In this example let us assume the total
sample weight was 8.42kg.
8.42 x 200 = 1684kg/ha.
In this case it would be best to lower the rear
door slightly and retest.