Plants need nitrogen. Unfortunately, they can only absorb this element in the form of soluble nitrate compounds. Excess nitrogen fertilisers can thus easily find their way into the groundwater where they are unwanted. Applying no more fertiliser than the plants can actually absorb is therefore practical environmental protection. The new Aero fertiliser spreaders from agricultural machinery manufacturer, Rauch Landmaschinenfabrik, put the mineral fertiliser exactly where it is needed and in just the right quantity. Motors from Faulhaber assist with the precision dosing.
Refining the spreading pattern
The conventional method for spreading mineral fertilisers on a field uses twin disc spreaders. The fertiliser falls out of the reservoir container behind the tractor onto two horizontally rotating discs. Their rotary movement ejects the grains up to 25 metres to the left and right as the machine drives over the field. While this allows large areas to be fertilised in a short amount of time, the distribution is performed at a fixed rate and is calculated on the basis of the total area. The spreading pattern is imprecise; in the case of irregular field shapes, in curves, and along the edges of roads, so there are inevitably strips that receive too little or too much fertiliser.
“We are able to avoid all of these drawbacks with our precise fertiliser spreaders,” says team leader, Maximilian Zimmer. “Here, the granulate is not ejected over a large area but instead lands on the field through a system of tubes in the correct quantity, and is finely dispersed. During this process, the machine can block out specific areas that require no fertiliser.”
Dosing system with switchable sections
The basis for such precision fertilisation is the MultiRate dosing system, which is the world’s first dosing and distribution system for granulated fertiliser for small-scale and precise plant nutrition for pneumatic fertiliser spreaders. It allows 30 spreading sections to be switched on and off individually. The applied quantity can be controlled individually for each section. This allows a reduction in fertiliser usage per unit area of up to 23% as well as a significant increase in yield.
The fertiliser granulate lands on the field through thirty individual tubes, precisely dosed in strips of 1 to 1,2 metres in width. Each individual infeed uses sophisticated technology. The fertiliser is guided through multiple funnels to six metering shafts with five segments each. These are CAN-bus-controlled and are equipped with cam wheels that divide the granulate into small portions. The granulate is then accelerated by a stream of air and transported to the outlet.
Motor speed controls fertiliser quantity
Each cam wheel segment is moved by a Faulhaber brushless flat motor with a special customer-specific gearhead and can be individually actuated. “The speed of the motor controls the quantity of the fertiliser applied,” explains Zimmer. “The machine can thereby ensure that the quantity per unit area is always the same in a curve formation even though each outlet travels a different radius.”
In non-rectangular field geometries, if rows overlap or the machine encounters the side of a path, the individual outlets can be automatically switched off and switched back on again later. Here the dynamics of the motor are essential. It must reach the precisely specified speed with no time delay, and must deliver a high torque.
This power comes from an extremely compact drive with a diameter of just 42 mm and length of 49 mm including gearhead, all fitted in robust steel and aluminium housings. The unit can thus withstand the unavoidable mechanical vibrations that occur in agriculture, and in as weather extremes.
Taking variable soil quality into consideration
The MultiRate dosing system driven by the Faulhaber motor enables precision farming in the true sense of the word. The tracks left by the tractor wheels are excluded from fertilisation, as are small biotopes or other non-agricultural areas that may be located in the middle of fields. Furthermore, the fertiliser quantity can be precisely adapted to different soils within a field. “The soil quality is recorded in detail in digital application maps,” explains Zimmer. “Using such maps and GPS data, the machine control can adapt fertiliser application to the circumstances fully automatically.
He summarises: “This precision technology not only protects the environment and the groundwater, it also lowers costs. The farm has a higher yield with less fertiliser; and with a lower granulate quality, the cost of the fertiliser is significantly lower.”
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