Solodisc injector system

After suffering dreaded compulsory injections at school, injections of a different kind are helping farmers all over the country to avoid the wrath of the Regional Council and Fonterra.

Farmers are always under pressure from the council and Fonterra to improve effluent management, which is fair enough. Stress not, though, as the Solodisc injector system I tested this month will allow you to flick authorities the bird, as there’s no way that your effluent will end up in a stream with this machine (unless you physically get stuck in there), in which case you probably deserve a fine for being a clown.

Back in the spring of 2011, I ventured into the deep south to test the Joskin Modulo 2 11,000-litre slurry tanker, and I was very impressed with what I saw. The most encouraging thing about the Joskin is the company’s dedication to build quality and its ability to think outside the square when it comes to making machines more user-friendly.

Fast forward six months to a recent field day run by Farm Chief, in conjunction with AMT Taranaki, where there was an identical tanker with a Solodisc 5.16m injector system, which Joskin had touring the country. The thing that first strikes you with this piece of machinery is how completely integrated it is: all the functions do more than one thing so you don’t need eight remotes on the back of your tractor. Also, because the implement is linkage-mounted, you don’t lose any manoeuvrability and can transfer weight from the tanker to the discs to achieve the best possible results.

Design and build

There are a ridiculous amount of options from the Joskin range; honestly, the mind boggles. But do remember there are many other options designed to meet every possible need, so if what you see here doesn’t appeal to you, don’t stress.

One example specifically for contractors may be the CARGO range. This is a chassis that you can hook different bins onto, so large contractors could put a silage bin on the chassis during grass and maize silage and then change to a slurry tanker or bath tub bin to give them winter work without the outlay of three separate machines.

For the test Modulo 2 machine, the optional ‘tank buttresses’ (where the linkage mounts) is bought into New Zealand as standard spec, so further down the track, if you want to add something like the Solodisc to the rear, the tank itself is ready to go. The tank is reinforced for this option in such a way that the rear implement weight is transferred through the whole vehicle not just the rear of the tank itself.

How it works

The functionality of the tanker itself doesn’t change; the loading arm still requires a separate remove valve but the opening of the rear valve is now taken care of in the hydraulic sequential block. All together you need three hydraulic remotes plus a dump for the continuous flow from the sequential block. One remote is for the loading arm, one for the hydraulic folding and unfolding of the disc ‘wings’, and the third is for the lowering of the tank linkage. As the linkage is lowered from in the cab the sequential block takes care of the following functions automatically:

  • Lowering speed twice the speed of the oil flow (essentially doubles the drop speed)
  • Opens rear valve
  • Start of the slurry macerator
  • Controls the automatic reverse of the macerator;
  • Opening and closing the hydraulic anti-drip pincers on the injectors
  • Precise contour following with constant pressure on the disc’s and wings

The linkage achieves this constant pressure by taking the wheels are off the ground and all of this weight is transferred onto the discs, in this case giving them 11,000 litres worth of penetration which, over 24 discs, is phenomenal.

The linkage

The rear linkage design on the tanker is built with both strength and stability in mind, in order to limit the side and vertical strains on the whole running gear. The arms are built short and wide so the weight on the back of the tanker doesn’t cause it to body roll. With Walterschied hooks on the bottom and two top links on the top giving you four point hitch, this ensures strength and stability while reducing over-hang to keep overall length down

The macerator

For those who don’t know what one of these is, essentially it works like a food processor on steroids. A good macerator is essential to make sure the injectors don’t keep blocking because dairy effluent particularly is full of fibres and stuff that the workers are too lazy to pick up so it gets hosed down the drain also known as ‘foreign objects’.

Joskin’s solution is a patented system with self-sharpening discs. A hydraulic motor at the top rotates a blade which then has rotating circular blades mounted to so that you will only put your hand in there once! When the blades strike against something that is too hard to chop, the rotation direction is reversed and it goes back and forward until the object is chopped enough to go through the injectors. Bear in mind, though, the eight-inch stone trap at the bottom of the tank will take care of the heavy objects before they even make it to the macerator, because rocks don’t float – believe it or not.

Discs and injectors

All folding models (including our test 5.16m) are fitted with double-acting hydraulic folding wings to meet 3m transport limits and to achieve the constant ground pressure. For safety on the road, the folding sys­tem is fitted with a locking feature which is done automatically when the wings are fully raised.

The disc and injectors themselves are designed kind of like a disc drill where they are all in line and individually follow the ground via spring tension. The cool thing here though is they actually have sideways movement as well which allows you to turn corners 15 degrees each way. This means the majority of the time you will only have to lift the machine at the headland and will not scuff the grass.

The self-sharpening discs are made of cast steel which make them super strong and penetrate the ground easily.

The discs are mounted on hubs with her­metically-closed and self-tightening co­nical bearings, which allow them to carry heavier loads (ie the weight of the tanker).

Each of the 24 injectors on our test machine is fitted with mechanical anti-drip pincers which automatically release the injection pipe when it touches the ground (and closes when lifted). Each pincer is shaped with rounded edges to limit the wear to the rubber injection cone to reduce ongoing maintenance costs.


In reality to be able to justify one of these, you need to be spreading a lot of effluent to make it pay off, so it is really targeted (but not solely) towards the contractor market. Effluent in this country will eventually end up having to be injected straight into the ground and with more and more evidence suggesting the possible nitrogen losses from spraying it into the air, who says this is too early to introduce such a machine? If you are looking at one of these bad boys, look at the Joskin first because you will not get a better designed, built and integrated machine on the market today.


  • Easy and simple to use
  • No mess, no smell spreading
  • Transfers weight off tanker onto discs for superior ground penetration
  • Completely integrated machine
  • Hydraulic sequential block reduces the number of remotes needed and automates a lot of the features
  • Macerator chops and cuts effluent to eliminate injector blockages
  • Disc/ injector mountings have left to right movement of 30°


  • A central greasing point would be handy as the compact nature of the implement relies on some creative greasing skills.

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Photography: Jaiden Drought

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