Fertilizer application method

BROADCASTING - APPLICATION OF SOLID GRANULAR FERTILIZER
A good fertilizer spreader distributes the fertilizer accurately, evenly and in a uniformed manner across the field. They use centrifugal, pendulum or pneumatic spreading:

Centrifugal or pendulum spreading:
The fertiliser is broadcasted by a rotating disc or an oscillating tube.
Pneumatic spreading:
The spreading device is a rail that is fed mechanically, and the granules are propelled pneumatically. 

Centrifugal spreading is very common. The fertilizer granules drop out of a hopper onto a rotating disc, which has blades that throw the granules. The granules are then ejected at high speed and distributed at each side of the tramline. The following factors are important for even spreading: 

  • Correct fertilizer spreader adjustment
  • Appropriate soil and weather conditions during spreading (low wind, dry and rut-free soil) 
  • Selecting fertilizers with appropriate physical characteristics
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When broadcasting with a centrifugal distributer, it is very important to consider the overlap distance between passes of the tractor on the field in order to ensure an even distribution of fertilizer across the field. This is because the concentration of granules decreases as distance from the broadcaster increases. The speed of driving also influences the distribution (see diagrams).
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SPREADER ADJUSTMENT
Fertilizer spreading machines must be adjusted for a given fertilizer with a predetermined working width. Spreader adjustments are provided by the manufacturers and include the following variables:

  • Output = dose in kg/ha x working width x movement speed
  • Working width = distance between two adjacent passes of the spreader. It is also the distance between the overlap points between passes. 


Over the last 25 years the broadcasting distance that spreaders can achieve has increased from 24 to 36 meters or even greater. The farmer must make sure that the fertilizer spreading machine is suited to the required width, and select fertilizer that is also appropriate. 

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Optimisation of spreading