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When, if ever, the weather decides to play ball, fertiliser spreaders will be out in force. The increasing price of fertiliser products has promoted sales of new spreaders - bigger, complex and potentially more accurate. Are they easier to use? Will they always spread more accurately? Whether you spend £5 or £50k on fertiliser each year, you need to get the most from every tonne.
It's very easy to pull the spreader out from the back of the shed, mount it on the tractor and drive off. Or even have a new lad on the job who tells you he knows all about it having done it in college. Checking the machine and using some fundamental ways of getting it on the tractor correctly will go a long way to having a even spread of fertiliser over the field.
Fertiliser needs to be spread accurately. Striping appears in the crop when the variation is greater than about 15%. The greater the variation the more obvious the stripes. Having no visible stripes does not mean fertiliser is spread evenly. The crop will still grow unevenly, will ripen at a different time, and can present harvesting difficulties.
How can we ensure even fertiliser spreading?
1. Mount the spreader correctly. The links have to be even. The top link adjusted so the machine is level. The spreader must be carried at the correct height.
For many years Practical Farm Ideas has suggested:
A. fitting a two-way spirit level (available from caravan shops) to the spreader frame (where level), so the arms and top link can be adjusted with the tractor on level ground
B. a measured length of chain is fitted to the spreader frame, so the chain just touches the ground at the right height.
This way you’ll get the spreader mounted properly without guesswork or the need of a measuring tape.
2. Ensure the spreader is in good condition. If there are worn parts, you’ll never be able to spread accurately.
3. Set it correctly. The book tells you, and the manufacturer or the dealer will help as well.
Getting the machine sorted through a company such as Spreader Calibration Services costs £160 or so. They’ll check it over, and may have the parts you need on board (extra). They then test it with up to two types of fertiliser. Their test uses trays spread across the ground and the tractor is driven, with the spreader working, through them. The quantity of material is then collected and poured into a special measure, which shows the spread pattern, which can then be analysed. They also advise on correct settings. The driver gets instruction and the farm gets a certificate for Farm Quality Assurance.
Their business is expanding, and they are looking for additional people to check out spreaders in various areas. Mechanical aptitude and a real interest in farm machinery needed, and training given.
Spreaders - there’s more to them than meets the eye
What condition is your spreader in? Spreaders don’t last forever, and, like all other machinery, need maintenance and repair along the way. Unlike most farm machinery, spinners don’t show their ailments obviously - you need to look for them. If we judge the machine on the state of the hopper and the amount of rust on the frame, we’re mistaken. These can look like new, but working parts can be worn.
Throwing a variety of granules 12 metres, 24 metres and maybe even 36 metres in an even spread pattern requires a carefully designed machine. Subtle changes in the shape of parts, through wear or misuse, will change the performance of the machine, perhaps significantly.
The spinner works by accelerating the fertiliser on the vane, each fert granule running along the surface of the vane, gathering speed. The longer the vane and the faster the rotation, the higher the speed attained and the greater the throw.
Spreader performance is assessed in conditions which are good to perfect. This means:
1. Low humidity, when fertiliser is hard and dry, the air through which it travels not laden with water vapour.
2. Correct PTO speed.
3. New condition vanes and spreading mechanism.
Many fertiliser spreaders work in different conditions:
- the air is humid (early spring, in between showers)
- tractors and drivers are happier working with lower revs
- the machine is worn
If the machine is incorrectly mounted as well, there’s every chance the material will go out unevenly.
The vane is the important part of any spreader. Made of stainless steel, they always look new in comparison to the surrounding paint work. The surface must be smooth, clean and slippery if the granules are to accelerate sufficiently to travel the distance you need.
Run your fingers on the inside of a vane on your machine. If it’s rippled, the material will be slowed down. The only way to repair is replace. Vanes are not overly expensive, and will spread many tons before getting worn. Once the ripples start, they soon increase in size.
See the vane surface is always really clean.
Sulphur fertiliser is often sticky
Sulphur Plus, Top and other products containing sulphur will often leave a residue on the surface of the vane - which reduces acceleration.
Spray the vane with WD40 and wipe clean every time you fill, and keep on top of the problem. Vicon pendulums don’t have the rippling problem , but are impossible to clean easily..
Worn bearings give a wobble
The slightest wobble in the disc is magnified many times and results in inaccurate spreading. The light load on disc bearings means they go on working without making nasty noises for some time after they have begun to wobble.
Checking fertiliser spreaders seems like the job for only a perfectionist or anorak. Yet the results of accurate fertiliser spreading can be spectacular in terms of even crop development, less lodging and improved yields. Experts can advise and give you a great deal of knowledge, and at the same time make certain your machine is up to the job.
Rob Foxall of Spreader Calibration Specialists is an expert who will get the best from your spreader. He's address is Rookery Farm, Roman Road, Wheaton Aston, Stafford, ST19 9QF. Tel: 01785 840849, M: 07768 945497 firstname.lastname@example.org
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