Just when you thought you had seen every cultivation system going, a new one comes along which rewrites the book. The Kelly multi-purpose harrow doesn’t use tines or presses and, while it has discs, they are very different to those used by “traditional” cultivators.
Instead, this trailed cultivator uses “strings” of small-diameter discs set out in a diamond shape so that the two front sets are angled to turn the soil in and the rear sets turn it back out again.
Designed in Australia as a means of shallow cultivating vast areas of land in double-quick time, the harrows are now built under licence in Denmark for the European market and available from Weaving Machinery in 6m, 9m and 12m working widths.
The discs, which are dished and made of hardened steel, each measure about 15cm in diameter and, interestingly, do not run on a shaft or axle. To allow the discs to follow ground contours, they are connected together more as a chain would be using an eye and a hook, in fact, each disc has just that – an eye on one side and a hook on the other.
To prevent any chance of discs becoming detached during work a small bolt is placed in each to reduce the gap of the open-ended hook.
At the end of the row where the chain joins the main frame, there is a bearing and a chain tensioning system. The latter is a lever system which employs a coil spring and insertable shims.
For the record, a 9m version has a total of 142 discs, each 16cm apart, to make up the four sides of the diamond shape – and the disc assemblies are set at 43 degrees to the direction of travel to allow the discs to peel off the surface of the soil.
Within the diamond shape there are also two smaller sets of discs to cultivate the land in the middle and ensure all the land is moved.
So, how does the Kelly multi-purpose harrow perform? Put to work in a stubble field near Market Rasen, Lincolnshire, where the soil was a reasonably light brash, a 9m version was hooked up to a John Deere 8430.
According to the manufacturer’s thinking this tractor’s 305hp was more suited to pulling a 12m version, and a 200hp tractor would have been quite sufficient to handle the 9m.
Maintaining an operating speed of at least 14kph is reckoned to be important if the soil is all to be moved. As the 8430 charged off across the field it was apparent that this was clearly the case.
You know you’ve reached top speed when the strings of discs start to bounce, but until that happens it’s a case of keeping going.
As a result, output rates are high, with up to 10ha/hr (25 acres) quite possible using a 9m model. Working depth very much depends on the soil type and the prevailing conditions although there is some fine-tuning available for softer conditions. Generally speaking though, a depth of between 2cm and 5cm would seem to be the norm.
Little maintenance is required. The bearings at the end of the disc chains are sealed for life and, apart from an occasional inspection of hydraulic hoses and the brakes, it’s only normal wear and tear that operators need to concern themselves with. Disc wear is claimed to be very low, with replacement needed only after many thousands of hectares, says the manufacturer. New discs will cost about £40 each.
For transport, the two wings are raised vertically and fold sequentially to create a low, stable, transportable unit which has a road-going width of less than 3m.
Price for the 6m is £29,800, the 9m is £49,000 and the 12m £66,000.