Even if there are recommendations on the bag, or in brochures and on websites, it is important that you calibrate your spreader with the products that you are using
reduced. Different settings would be required for fertilisers with different particle sizes.
If the fertiliser you have selected has a wide particle size range, some granules will travel a long way from the centre line while others will not. If these different sized granules are also sources of different nutrients (i.e. some nitrogen and potassium) then it is possible that striping could occur following application, even if the overall rates are correct, so a narrow particle size range is essential for the uniform application of nutrient across an area.
Dusty fertilisers affect application rates and also affect how the operator uses the spreader and when, for example in windy conditions or when other people are in the vicinity.
Calibrating your spreader
Spreaders should be calibrated prior to use. Even if there are recommendations on the bag, or in brochures and on websites, it is important that you calibrate your spreader with the products that you are using. The advice in literature or on the bags are guideline recommendations only, and you need to calibrate your spreader and setting to your individual equipment and conditions.
The calibration process is relatively simple:
• First, check your spreader over visually to ensure all parts are present and correct and in good working order.
• Work out your walking speed by timing yourself over a set distance, do this three times to get an average.
• Set out calibration trays to catch the full width of fertiliser as it is spreads. Walk through the trays at the correct speed with the spreader applying fertiliser.
• Weigh the fertiliser from the trays and assess the spread pattern, this will tell you how wide apart you should walk.
• Put a known quantity of fertiliser into the hopper and spread it in a straight line. You can then measure the distance you have covered and work out your application rate.
• Adjust the spreader apertures to the required setting for your required application rate.
If you prefer, you can get a specialist company to calibrate your spreader for you. Companies such as Spreader and Sprayer Testing Ltd offer an MOT-style check and calibration of your application equipment.
Application advice
Fertiliser application still needs some human intervention, and with this
another variable is added. Walking speed will have a big impact on application rates, so it is important to note what speed is advised per spreader. Guideline settings are normally based on 5km/h (3mph) which is considered normal walking speed. Increasing walking speed will mean that for a given time a greater distance will be covered, but since the flow rate does not change according to speed, this also means that the application rate per m2
decreases.
This is further compounded by the fact that, with increasing walking speeds, the spinning disc will also increase in speed and, with this, the distance that the granule is thrown from the spreader increases. The result is that the same quantity of material is being spread over a wider distance (and also forward distance) meaning a reduction in application rate. The reverse is true if you decrease your walking speed so, if you’re doing a lot of spreading in one day, remember to recalibrate yourself regularly!
It’s important to try and keep the
spreader parallel to the ground so that an even spread pattern is achieved. Tilting the spreader too far forwards results in the application of a lot of material in front of the machine, creating a band of over-application within the centre of the spread pattern. To increase the uniformity of application, it is best to apply the fertiliser in two passes at half rate, as this minimises the risk of over/under applying due to incorrect spreader spacings. These two passes should run at half spacings run parallel to each other to ensure the best spreader pattern over- lap. Double passes with the second pass conducted at right angles is also practiced, however, incorrect overlap can still occur on both passes resulting in a ‘checkerboard’ effect.
Aftercare
Always empty the remaining fertiliser out of the spreader and return it back into its original bag, sealing it tightly to prevent moisture entering. Clean the spreader in an appropriate
area using either compressed air or water to ensure that the aperture, helical cone and spinning disc are all clean with no remaining debris. If the cone or spinning disc is not cleaned following application, it can alter the spreading characteristics for the next application. Ensure the spreader is dry before using it again to avoid the product forming clumps.
Some common fertiliser problems and causes
Problem: Dark stripes Cause: Swath widths to narrow/close
Problem: Light stripes Cause: Swath widths too far apart
Correct walking pattern
Incorrect walking pattern
Problem: ‘Checkerboard’ effect Cause: Double pass at right angles used with incorrect spacings (too near/too far apart)
Problem: Tiger stripes in turf Cause: Walking too slowly with rotary spreader causing a curved band of fertiliser to be applied
Problem: Spotting on turf
Cause: Application rate too low (various reasons for this)
If you’d like advice on your choice of fertiliser or guidance on applying it, contact your distributor rep who will be pleased to advise you. A list of Scotts distributors and the contact
details of the Scotts Turf & Amenity technical team can be found on the website at
www.scottsprofessional.co.uk.
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