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71
GRAANGIDS
2016
GRAIN GUIDE
How to calibrate your planter
Successful cropping has developed into a
highly specialised process. Planters play an
extremely important role in the process – par-
ticularly with respect to the accurate spacing
of plants and the plant depth of seed. The ac-
curate dispensing of fertiliser is also important.
The function of a planter
A planter has the following basic functions:
• It opens the fertiliser furrow up to the correct
depth for fertiliser placement.
• Correct measuring of calibrated fertiliser
and placement.
• It opens the seed furrow up to the correct
depth for seed placement.
• Correct measuring and placement of seed.
• Closing of seed and fertiliser furrows.
• Compaction of the soil for effective soil to
seed contact.
The above functions must all take place simul-
taneously and their effectiveness should not be
speed sensitive.
Seed dispensing
The primary function of planters is to dispense
seed correctly. Seed can be dispensed in the
following ways:
• Conventional horizontal tray dispenser.
• Tray dispenser dispensing at an angle.
• The finger-wheel dispenser.
• The vacuum tray dispenser.
Tray dispensers are still used, but because
seed grading is no longer that accurate,
vacuum dispensers and finger-wheel
dispensers are used increasingly.
Dispensing and placement of fertiliser
Fertiliser is dispensed as granules or in liquid
form. Granular fertiliser is dispensed positively
with a star-wheel or worm dispenser.
Liquid fertiliser is dispensed with a squeeze
pump, or – these days – with a special liquid
fertiliser pump.
Calibration of the planter
When a planter is calibrated, wheel slippage
of the planter drive wheels is an important
component to take into account. It is important
to calibrate the planter in the field to be
planted to compensate for wheel slippage.
Different soils will cause different wheel
slip percentages.
Calibration of fertiliser
Fertiliser dispensing can be calibrated as
follows:
• Mark out a distance of 10 m in the field.
• Catch the fertiliser from one of the fertiliser
delivery tubes in a suitable container across
the 10 m distance, while the planter moves
at a normal working speed.
• Weigh the fertiliser caught in the container.
• The fertiliser delivery in kg/ha can be calcu-
lated as follows:
Mass of fertiliser delivered over 10 m in grams
Planter’s row spacing in metres
• Repeat the process with the other planter
rows to ensure that the delivery is the same.
• If the delivery has to be changed, the gear
combinations between the drive wheels of
the fertiliser mechanism should preferably
be changed rather than increasing or
decreasing the delivery.
Calibration of seed
Seed dispensing can be calibrated as follows:
• Mark out a distance of 10 m in the field.
• Set the plant depth so that the seed is
placed on the soil.
• Count the number of seeds delivered in a
row over the distance of 10 m.
Continued on p. 72