17 August 2001


Subsoiling is an essential loosening task on many soils.

But does it have to be carried out as an expensive

operation separate from other cultivations?

Peter Hill reports on growers who prepare seed-beds

and rid their soils of compaction in one go

POTATOES need deep, fine seed-beds to produce their best yields, which inevitably means something of a power-intensive round of cultivations to achieve the desired results.

But at Park Farm, near Leominster, Herefordshire, grower Bill Smith has found a way of removing one operation from the cultivation sequence. By using a subsoiler designed to work with pto-driven implements like rotary tillers and power harrows, he soil-loosens and finishes seed-bed preparation in one go.

"I am really pleased with the way the outfit works," he says. "Previously, we would have subsoiled our potato ground only where it really needed doing. But now, because we can subsoil at no extra cost, all our land gets the soil-loosening treatment."

A 3.3m (130in) Dowdeswell Powervator rotary tiller, fitted with a spike rotor, is used for the last soil working operation before ridging up. It works deep, pummelling the medium to heavy soil into a fine tilth. It is now used in partnership with a six-leg McConnel Vibratilth subsoiler. This cut-down version of the Shakaerator has a two-bar frame carrying its distinctive sharply-curved tines in two rows.


An eccentrically-weighted flywheel, driven by hydraulic motor (rather than by pto as on the original implement) induces a high resolution vibration through the frame, which is said to ease the passage of the tines through compacted soil.

Bill Smith put the outfit to the test across 40ha (100 acres) last year and this was enough to convince him that the one-pass technique had merit. A Vibratilth was bought and used for the entire potato acreage this spring, operating typically 30cm to 35cm (12in to 14in) deep.

"We used it on a 150hp Case-IH CS150 tractor, but did not really notice that the outfit needed any more power than operating the Powervator on its own," he says. "That is probably because the Powervator has less work to do in the loosened soil, and because any compaction caused by previous cultivations has been taken out, it does not keep trying to climb up and over it."

Implement lift capacity is potentially more of an issue. With the Powervator pushed back from the tractor by slotting the Vibratilth in between, the tractor needs plenty of lifting power as well as the ability to handle the weight once it is up in the air.

This was not a challenge for the generously-equipped CS150 and nor was coupling the two implements.

"The Vibratilth is designed from the outset to work with other implements, so everything is in the right place," says Bill Smith. "You just need an extra-long pto shaft."

This autumn, the plan is to use the Vibratilth on the front of a power harrow for oilseed rape and cereal seed-bed work.

"It is not often you come across an implement that makes a genuine difference to your operating costs and the quality of your work," says Mr Smith. "But this is one such case. I am really delighted with it."

Lincolnshire salad and vegetable crop growers express similar enthusiasm for placing a shallow subsoiler in front of a power harrow. It not only takes out any residual compaction from previous operations, but ensures the harrow itself does not leave a smeared pan in wet, sticky silts.

"I am not a power harrow fan, but we do not have any choice but to use one," says David Sharpe, farm manager at T &#42 Clements & Son, Benington, near Boston, Lincs. "I feel much happier about using one with the Pancracker, however, because we are not causing the same problems."

The Pancracker is produced by Gary Skipworth Agricultural Supplies as a single-beam implement carrying simple straight-leg tines individually adjustable for depth.

It has replaceable shins to guard against excessive wear of the leg itself, and can be had with plain or winged points. Growers have so far opted for the plain point to ensure the implement lifts and loosens the wet soil without bringing it to the surface.

Down below

Although the silty soils in this area can look dry and in perfect shape for planting up with salad or vegetable crops, down below things can look a bit grim, especially after the sort of wet autumn, winter and early spring experienced over the past 12 months.

Repeated working with a power harrow to get a fine tilth tends to produce a smeared pan that acts as a barrier to roots trying to reach moisture.

Running with the Pancracker between tractor and power harrow, set about 10cm (4in) deeper than the rotating harrow tines, takes out this barrier while preventing further damage from the power harrowing operation.

David Sharpe runs one 6m and a pair of 3.5m subsoiler/harrow combinations and has found that, far from slowing the job or increasing power requirement, the soil loosener speeds things up.

"Loosening soil ahead of the power harrow tines gives them a much easier time," says David Sharpe. "The harrow works a lot more smoothly because it is not having to work in compacted soil and, in fact, the tractors are running a couple of gears faster. So we are using less fuel and I guess tine wear is going to be reduced too." &#42