Back to basics 3
In the third and final part of his ‘Back to Basics’ article on fertilisers, Scotts International Technical Manager,
Stuart Staples, advises on selecting and calibrating a spreader and tackles common problems with fertiliser application
Spreader types
There are basically two main types of granular fertiliser spreaders; drop and rotary. Drop spreaders, as the name suggests, drops the fertiliser granules through holes along the bottom of the hopper. Altering the spreader setting will in turn alter the size of these holes and the flow rate of fertiliser and, therefore, the application rate. These types of spreader are best for precision application over smaller areas and, for this reason, they are perhaps not the best choice for larger areas such as sports fields. Great care needs to be taken with the walking pattern and getting the correct amount of crossover on each return run, since fertiliser is either applied at 100% rate or 0%. This means that if the walking pattern is not correct, you will either have small stripes where no fertiliser has been applied resulting in yellow turf or, where fertiliser has been applied at twice the desired rate, stripes of very dark turf and possibly scorching. Rotary spreaders are more suitable for applying fertiliser to larger areas and are more commonly used in the maintenance of sports fields. Instead of the fertiliser dropping straight down from the hopper onto the turf, the granules will first hit a spinning disc(s) that propels the granules over a wide distance and so speeds up the application process. Accurate swath widths are also very important with rotary spreaders but are less critical than with drop spreaders. This is because the amount of product applied gradually decreases at the edges of the swath width, so there is no on/off line as with drop spreaders making misapplication errors less visible. Rotary spreaders may be tractor mounted or pedestrian propelled. The choice depends on the desired accuracy and the total area to be covered, combined with your fitness and enthusiasm!
Selecting a spreader
There are many factors that contribute to a well-designed and constructed fertiliser
spreader but, for turfcare professionals, there’s only one aim; the accurate application of your selected fertiliser. So, what is important?
The most important thing is the compatibility of your spreader with your selected fertiliser. From a practical perspective, they should be comfortable to operate and well constructed for longevity. Wheels should have flotation tyres to minimise the impact to turf, especially when using it with a full hopper.
The best rotary spreaders have some kind of mechanism that can alter the spread pattern according to the different physical
characteristics (particle size and bulk density) of the available granular fertilisers. If your spreader does not have this feature, it can only accurately apply one type of fertiliser. Within the turf industry, the most popular type of rotary spreader that can be adapted to accommodate a wide variety of fertilisers with different physical properties uses a helical cone to adjust the spreading pattern. The Scotts AccuPro 2000 and SR-2000 models are popular examples of this patented technology. By adjusting the helical cone, the location of the fertiliser coming from the hopper to the spinning disc can be adjusted and, therefore, fine-tuned to give a consistent spread pattern and left/right swath width.
How fertiliser selection can affect spreader performance
The characteristics of your selected fertiliser can have a big impact on the performance and reliability of your spreader. Bulk density will affect the weight of product flowing through the aperture. Denser material will require less granules to flow through versus a product with the same particle size that is less dense. Granule size is very important. Larger, heavier granules will travel further once propelled by the spinning disc of the rotary spreader and therefore altering swath width. Conversely, smaller, lighter granules will not travel so far and the swath width will be
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