Kuhn Optimer 4003 review

We put the Kuhn Optimer 4003 to the test in the eastern Bay of Plenty.

Whakatane claims the award for the most sunshine hours in the whole of the country and is one of the main reasons the area can grow some of the best maize grain crops in the country.

While the weather has a big part to play in any cropping situation, getting the ground worked up and then planted in a timely and efficient manner also has a significant effect on the outcome.

Nigel Timbs, the owner of Stockland Agri Limited, knows this all too well. Although he started out solely as a fencing contractor in the Bay of Plenty region, the business has grown to include some agricultural contracting work, and more recently, contract maize grain growing where he crops around 150 hectares of ground every year.

With a continual rotation of maize grown on fertile river flats, there is a large amount of stubble and crop residue that needs to be incorporated back into the soil with a disc harrow after harvest. This usually takes place soon after harvest so the ground can be left fallow over winter before it is ploughed and cultivated in the spring.

Last year, when looking to increase the efficiency of the operation, Nigel went in search of an upgrade for an older three-metre Lemkin disc harrow that he had been using. He was impressed when he saw the Kuhn Optimer in action at a demo. It was soon added to an ever-growing collection of Kuhn equipment in the Stockland Agri yard that includes a Kuhn VM123 reversible plough, HR3002 power harrow, and an SD4000 drill. Each was sold by local dealer W J Dippie, who has continued to provide excellent local sales knowledge and backup service when required.


The Kuhn Optimer 4003 is a compact trailing disc harrow that has been designed specifically for cultivating at speed to a shallow depth and incorporate residues. To do this, it firstly uses large 510mm diameter scalloped discs set at aggressive opposing angles to cut into the soil.

The 32 discs are arranged in two gangs across the four-metre width of the machine and run on slim individual carrier arms that give plenty of clearance for soil and stubble movement through the machine. Each disc is mounted to the carrier arm on an individual cast hub that houses a completely sealed bearing unit, which is greased for life, saving time and lowering the maintenance requirements.

Fairly common but still good to see is that the carrier arms are mounted with rubber blocks sandwiched in the clamps on the frame. This allows individual movement to prevent damage if a solid object is struck.

The overall working depth of the discs of the machine can be varied anywhere between 30 and 100mm. This is easily changed without tools with a screw adjustment stopper that incorporates a clever scale and a simple pin and hole set up on the rear roller.

Optimer 10


Set behind the discs is a row of light adjustable straight spring tines that further help to level and bury residues, and although they don’t look like much, it is surprising to see how effective they were without blocking up in the large amounts of maize trash. The working height is adjustable and the can be lifted clear of the ground if not required It uses a simple pin and hole set up. The design cleverly incorporates a handle with enough leverage to make it easy to lift the tines up and down when adjusting them with little effort.


All components on the machine are carried on a well-built, robust yet compact mainframe, with large 400/55 x 22.5 flotation tyres that are used to lift the machine out of the ground when turning on the headlands or for transport. To keep the overall transport width under three metres, there are outer wings on either side, which can be hydraulically folded and carried vertically. Cleverly, when the outer wings are in the working position, there is a choice on the folding rams between a fixed position (to keep the machine level and rigid), and a slotted hole (which allows the wings to move up and down follow the ground contours). It seems a good idea to have the choice.

Up at the front of the machine is a solid two-point hitch that allows movement in all directions. This hitch also allows for tighter headland turns and means that the machine can easily be levelled on the three-point linkage for a level finish. A telescopic drawbar would be an improvement to the machine although not a problem in Nigel’s situation. If you are running wide duals, the short drawbar will limit the turning ability. A hose needle keeps hoses and cables out of harm’s way, and a well-placed stand makes it easy to unhitch. Although overall the machine is well built and tidy, a passing comment on the day was that already after only six months, the paint work had started to fade and show some blemishes, which maybe is a testament to Whakatane’s claim to the highest sunlight hours in the country.

Rear Roller

Like most similar machines, the Kuhn Optimer offers a range of rear rollers to suit the intended usage. There is the T-Ring roller, which is a wide-spaced, open press ring roller, the T-Liner, which is a deep ring steel drum roller, and the Packliner, which was fitted to Nigel’s machine. This is a large 600 mm diameter deep ring roller, which is coated with a hard rubber that enables it to work well in damp conditions without soil sticking to it. There are still scrapers fitted to keep it clean as well. It was reasonably damp the day I was there, and the roller was handling it well. It provides excellent consolidation across the width and further breaks down clods in the soil to leave a firm level surface.


Interestingly, Kuhn recommends around 200hp on the front of this four-metre machine to achieve good forward speed. However, on the day, a John Deere 7530 on the front with 180hp on tap seemed to be managing a respectable forward speed of around12–14 km/hr and achieving a good finish but it was on the dead flat ground. Having covered close to 150 hectares of ground, Nigel is so far pleased with the results and his decision to purchase the machine. He is pulling it with the same tractor and managing similar forward speeds yet covering an extra metre of ground with every pass, lowering running costs and improving work rates. It was also noted that the material flows through the machine better leading to fewer blockages and that residue has broken down noticeably faster than in the past.


The verdict

Such machines that combine shallow cultivation and incorporation of crops stubbles with reasonably fast forwards speeds, and therefore, high output work rates, have gained huge popularity in Europe and are appearing more and more in New Zealand. I have been lucky enough to see roughly five examples from different manufacturers over the last six months; all had good points in their own right.

In my opinion, the Kuhn Optimer offers a simple yet reliable machine that is easy to set up and simple to adjust. It was achieving good results, and I was impressed to see that this four-metre model was working well behind a 180hp tractor. I guess, for me, the bottom line is that the owner Nigel is incredibly pleased and impressed with the results from the machine and the support and backup from his local dealer.


  • Large scalloped 510 diameter discs
  • Individual carrier arms with rubber blocks allow movement away from solid objects
  • 4m working width with a 3m transport width
  • Outer wings can be on a fixed level or float to follow contours
  • Large flotation tyres minimise compaction and provide stable transport
  • Large diameter, rubber coated heavy rear roller that can work in damper conditions


  • Telescopic drawbar would be an improvement for those running duals
  • Paintwork showing signs of fading
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