Hay & silage: Fieldmaster GMM multicut rotary mulcher

By: Brent Lilley, Photography by: Brent Lilley

Fieldmaster GMM multicut rotary mulcher The mulcher did a tidy job in the vineyard dealing with the vine prunings laying in the long grass Fieldmaster GMM multicut rotary mulcher
Fieldmaster GMM multicut rotary mulcher Two pairs of triple stack blades a used on the 1.8m wide mulcher Fieldmaster GMM multicut rotary mulcher
Fieldmaster GMM multicut rotary mulcher Fieldmaster GMM multicut rotary mulcher
Fieldmaster GMM multicut rotary mulcher A highly versatile machine capable of mulching a wide variety of materials Fieldmaster GMM multicut rotary mulcher
Fieldmaster GMM multicut rotary mulcher This smaller 1.8m mulcher only requires around 50hp to tackle even the toughest tasks Fieldmaster GMM multicut rotary mulcher
Fieldmaster GMM multicut rotary mulcher With the roller and mulch plate down when driving forward, the gorse was chopped up into a fine mulch Fieldmaster GMM multicut rotary mulcher
Fieldmaster GMM multicut rotary mulcher When backing into gorse, the roller is hydraulically lifted out of the way to knock down even the tallest material Fieldmaster GMM multicut rotary mulcher
Fieldmaster GMM multicut rotary mulcher A heavy-duty steel mulch plate above the roller which, when closed, holds the material under the machine longer to chop it up finer Fieldmaster GMM multicut rotary mulcher
Fieldmaster GMM multicut rotary mulcher Protected greasable bearings on the rear roller feature a scraper to prevent material wrapping around the shaft Fieldmaster GMM multicut rotary mulcher
Fieldmaster GMM multicut rotary mulcher Slip clutch on the main PTO driveshaft to the mulcher Fieldmaster GMM multicut rotary mulcher
Fieldmaster GMM multicut rotary mulcher The height of the mulcher is set with two adjusters and a scale on each side of the machine Fieldmaster GMM multicut rotary mulcher
Fieldmaster GMM multicut rotary mulcher Two hydraulic rams and a steel frame are used to lift the roller and mulch plate Fieldmaster GMM multicut rotary mulcher
Fieldmaster GMM multicut rotary mulcher A robust A-frame headstock is used to mount the mulcher to the tractor and a chain guard prevents material from flying out the front Fieldmaster GMM multicut rotary mulcher

Testing machinery to the limit is what we love doing here at Farm Trader and this month Brent Lilley got to do just that when he took Fieldmaster’s multicut mulcher for a spin.

Hay & silage: Fieldmaster GMM multicut rotary mulcher
A small mulcher with a big appetite

To prove that Farm Trader not only showcases the biggest machinery, but also the best, this month I headed north on a glorious spring day to Kumeu, west of Auckland — a largely lifestyle-block area.

Here I caught up with Lance Pawley, owner and founder of Block Busters, a lifestyle block maintenance business specialising in putting the 'life' back into lifestyle blocks. Block Busters is based in Redvale, north of Auckland, and covers an area from the North Waikato to Whangarei. It has a fleet of three smaller tractors that can be transported on a trailer behind their utes. This company offers a wide range of services, including mowing and mulching, cultivation and seeding, spraying, fertiliser spreading and more, with a full range of implements, but I had eyes firmly on the 1.8-metre-wide GMM multi-cut mulcher from Fieldmaster.

The test

The mulcher was on the back of one of Block Busters' 47hp John Deere 3720 hydrostatic drive tractors. Pawley, being pretty keen to show off the capabilities and versatility of the mulcher, had arranged two different sites to test it out at. First up was a vineyard with prunings from the vines laying in the grass between the rows. The task was to mulch these prunings up and cut the grass at the same time. The 1.8-metre width of the machine was ideal as it could easily fit down the 2.4-metre-wide vineyard rows without damaging the vines or the posts, and the machine did an excellent job leaving a tidy finish.

Later in the day we headed across to another property in nearby Coatesville, where Pawley had been saving up a job mulching gorse that was up to three metres high in places. I'm sure most will agree this is a fairly tough ask for any mulcher, even more so for one with only a 47hp tractor on the front. I have to admit, it was rather impressive to watch this small tractor backing into gorse twice as high as it, knocking it down and turning it into fine mulch.

Design and construction

Fieldmaster uses a modular design concept on almost all of its mulchers, enabling them to be configured for a variety of different situations and assembled quickly to keep costs low. At the front is a robust headstock with category-two linkage pins and a slotted or fixed top link hole. The headstock is bolted on to the deck of the mulcher and there are pre-drilled holes allowing it to be flipped and then bolted back on, enabling the mulcher to also be used on a front linkage.

The deck of the mulcher is built using heavy-duty twin 5mm steel skins with reinforcing under the deck for extra strength where it is needed. The sides on the mower use a heavy-duty pressed concave skid on the bottom, which is 80mm wide and built from 12mm steel for an extended lifespan and wide ground contact. They bolt onto the deck with four bolts on each side in a slotted hole and a coarse-threaded adjuster allows the cut height to be adjusted relatively easily by using a scale on the side of the mower. The deck and the skids, once again, have pre-drilled holes so a variety of extras, such as front and rear rollers, mulching shrouds, chain guards, etc. can be bolted on to fit individual requirements.

After it is laser cut and welded, all the steel on the machine is bead blasted and then treated with a zinc undercoat and finished with a baked-powder coat on the surface to give a longer lifespan and an exceptional finish. Those with an eye for colour coordination will be pleased to know Fieldmaster is happy to paint the machine in your choice of colour — the Block Busters machine was painted in its trademark yellow.

The heavy-duty high quality build of this machine is second to none and this leads to probably the only genuine disadvantage it will have in some situations over other mulchers available: its heavier and longer, which leads to more weight being transferred to the tractor. Not too much of a problem until you get in to some seriously steep situations. I witnessed this on the test day, with the front wheels of the tractor wanting to lift of the ground in the steeper areas — but remember this was only a 47hp tractor.


All Fieldmaster GMM mulchers feature a direct driveline to keep the power requirements low. The power comes through the driveshaft from the tractor to a centre gearbox that splits it left and right. I was pleased to see a slip clutch on this machine — something I've criticised machines for in the past for lacking these. From the centre gearbox the drive is transmitted through shafts to the 90 degree gear boxes on top of each of the two rotors. The driveshafts also incorporate rubber couplings that will take the shock if objects are struck by the rotors and the gearboxes are oil lubricated for low maintenance and high longevity. The shafts for the rotors meet the housing above very close to the deck of the mower leading to less chance of material wrapping and damaging the seals and bearings.


The blades fitted are in a triple stack design using a straight flat 100 by 10mm thick fail blade which then has two smaller 60 by 10mm blades bolted onto it to create a Y shape. This results in the material being cut three times every time the blade hits it to finely chop and mulch it up. From past experience, I would suggest they are very versatile, ideal for mulching a wide range of materials, including Kikuyu, rough pasture and weeds, crop stubble and, as I was to witness on the day, vineyard prunings and mature gorse.

If the triple-stack blade isn't versatile enough then Fieldmaster also offers a selection of other blades to suit, including an extra heavy-duty axe head flail for use on big scrub and gorse, a thin gold-tipped blade that is ideal for clean cut grass mowing, and a tungsten-coated blade for use in abrasive situations, such as on sand. With only two blade holders on each rotor using only a single heavy bolt to hold the blade on, they can be interchanged very easily and quickly. All of the blades are also reversible to increase the lifespan and lower operating costs.

Rear roller

I have mixed feelings about rear rollers on the mulcher. In some situations they are ideal and in others they will hinder the operation somewhat, so I was very intrigued and impressed by an idea that Fieldmaster, together with Pawley, developed and is now available on all Fieldmaster mulchers. The roller mounts to the rear of the mulcher on two steel arms and hydraulic rams lift the rear up and clear off the machine when it's not in use, and lowered when it's required. This mounting also includes a steel mulching plate to hold the material in the machine, chopping it up even finer, but no scraper to keep the roller clean.

In practice, this setup worked excellently in the vineyard. Having the roller down allowed the machine to follow the ground closely without scalping, while holding the prunings under the mulcher till they where finely chopped. Later in the day when we attacked the gorse, the hydraulic roller proved just how versatile it could be. When lifted up out of the way it acts as a pushing bar when backing into the standing gorse to knock it down, feeding it under the mulcher. With an experienced operator the roller can be lowered again, as the tractor drives forward to help finely chop the material once its laying on the ground.


The GMM multicut mulcher from Fieldmaster is another fine example of a quality product that has been designed and built here in New Zealand to suit the conditions. It was also great to have the opportunity to check out a business like Block Busters, that has grown to meet the demands of the area it operates in. Some key features of this mulcher that set it apart from others are its triple stack blades that mulch the cut material and the rotary design with a direct drive line that lowers the power requirements. Testament to the lowered power requirements is the size of gorse that was tackled with a tractor that was only 47hp. The standout feature for me, though, was the hydraulically-mounted rear roller adding to the versatility and situations where the GMM mulcher can be used. This roller is a credit to the team at Fieldmaster, which works with the people operating its machinery towards common goal to improve its New Zealand-made products.

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