Part mulcher, part harrow is how German firm Saphir describes its novel Grindstar.

It is designed to work just 20mm deep to encourage volunteers and weed seeds to germinate without losing too much moisture from post-harvest stubbles.

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Work is done by the seven ground-driven knives carried on each 75cm-diameter, counter-rotating rotor.

These are mounted on sprung parallelogram linkages with 200mm of travel, allowing them to faithfully follow undulations without ever digging too deep.

The aim is to remove soil from the roots of the previous year’s crop, lightly cover weed seeds and condition harvest residues to encourage quicker decomposition.

In essence, it does a similar job to a spring tine or compact disc harrow but at a shallower depth.

That means power requirements are relatively modest – about 25hp/m – to hit target speeds that can top 18kph.