While the trend towards ever lengthening gangs of disc harrows continues apace, Dominic Kilburn looks at a lighter and more compact tractor-mounted option available.
"Size isn't everything," someone once said about something.

The same can't be said for the trailed disc harrow market in recent years where, on the face of it, size is everything.

Visitors to last year's Tillage events in Lincolnshire and Gloucestershire would have seen the latest in large disc technology followed by double presses being trawled around the sites by equally large high horsepowered tractors. And, as reduced tillage thinking currently plays on the minds of most arable farmers in the UK, this over-sized kit has certainly found its niche on farms around the country.

Visitors to the same events might also have seen a tractor- mounted disc harrow being put through its paces. Already a familiar sight in the smaller (Vari-Disc Duo) version, of which over 500 units have now been sold, the weightier Vari-Disc Quad performs a more aggressive job in the field and achieves a better mixing action than its smaller brother, says manufacturer Opico.

The concept of this Dutch-designed machine is simple enough. A linkage-mounted heavy duty 140 x 80mm box-section frame supporting four rows of angled scalloped-discs- 28 discs for the 3.0m Vari-Disc Quad and 32 for the 3.4m version. Each disc (with 425mm spacing) is independently suspended while each row is manually adjusted to the desired cutting angle.

At the rear of the implement a standard crumbler roller or optional flexi-coil roller is fitted for adjustable depth control and consolidation. The roller's width slightly exceeds that of the discs to ensure the full width is covered.

Opico's managing director, Jeremy Coleclough believes the Vari-Disc Quad's strength lies with its aggressive soil moving capabilities. "We think it competes directly with traditional discs, but gives a better mixing action," he says.

Although lightweight in comparison to other discs, the Vari-Disc Quad has a weight variation from 1800-2180kg (depending on which model) and a minimum power requirement of 110hp.

Straight in after harvest

Charles Smallwood of RK and CE Smallwood, farms with his father Ken at the Homestead, Sutton-on-Derwent near York. He purchased his 3m WH300 Vari-Disc Quad in time for autumn cultivations in 1997.

Mr Smallwood's combinable crops include winter wheat, barley, and rape while protein beans are grown for the farm's herd of beef cattle. The soil type is mainly heavy but includes a mixture of black sands.

The Vari-Disc Quad goes straight in after harvest of all crops, prior to ploughing, and usually twice over for rape stubble. On occasions it is used to break down the soil after the plough, says Mr Smallwood. "In 1997 the ground was really hard and we'd tried other discs and cultivators which hardly left a mark," he explains. "We just set up the Vari-Disc Quad and it literally pulled the discs down into the soil. If anything we had to re-adjust to prevent too much disc-to-soil contact."

Burial of trash and weeds from the mixing action is superb, maintains Mr Smallwood. "The versatility of having four rows of discs on one implement means that one pass with the Vari-Disc Quad equates to two passes with conventional two-row discs.

"Blockages are rare in comparison with conventional discs mainly because there's no axle and adequate disc spacing. If there is a build-up of trash then it's easy to just raise the implement on the linkage and it drops out," he adds.

Mr Smallwood operates the Vari-Disc Quad disc cultivator at a 4.5" depth and at 5mph-plus speeds with a 110hp 2640 Massey Ferguson tractor. He reckons that on a really good day he could complete up to 40 acres. "Going faster doesn't change its performance - no ground within its width is left unturned and, as many of our fields are long and narrow, the additional speed and manoeuvrability both in the field and for road transport is an advantage," he says.

With many farmers recently suffering the consequences of using heavy equipment on wet land, Mr Smallwood believes he has the answer with the Vari-Disc Quad. "Compaction is of great concern to us and in the wet we stay well clear of the land with big machinery but can run the Vari-Disc Quad without causing soil damage or clogging up. If necessary we'll run it without the crumbler roller to lighten the load."

The Vari-Disc Quad has also proved a great levelling tool on uneven land and in some years producing good seedbeds straight after the plough - completely replacing the power harrow. "Other disc cultivators have the expense of requiring another implement to prepare a bed properly," he says.

Maintenance is simple, he continues with discs, bushes and bearings readily accessible and quick to change. "I just get hold of each disc and see if there is any movement.

"It's a versatile, simple and low cost implement to run. Being robust it should last for years, saving us money at times when it replaces the power harrow and reducing down time from minimal maintenance.

Chop and bury straw

John and Geoff Hardy have diversified in every sense of the word. They farm 450 arable acres, pigs on contract, have a caravan holiday park and , since 1991, opened Hardy's Animal Farm to the public.

Gray's Farm is situated on Lincolnshire's east coast at Ingoldmells, featuring a clay loam predominently on the heavier side, says John Hardy.

Problems with smoke-filled caravans had prompted the Hardys' to chop and bury straw long before the straw burning ban came in and, according to Mr Hardy, it is all part of the process of gradually rebuilding the soil's fertility since it was flooded by sea water in the 1953 storms.

"We previously only used a plough and furrow cracker to bury the straw and trash prior to creating a seedbed, so we tried a Vari-Disc Quad disc cultivator in 1997. We were told to go twice over the winter wheat stubble, which we did diagonally across the tramlines, and it worked. All the trash was buried, it was left to mulch and then drilled with a Lely Polymat combi."

Mr Hardy says that to keep a good cultivation balance on the farm, the Vari-Disc Quad (pulled by a 135hp MF 8110) is used instead of the plough in two out of every three seasons and occasionally, in wet autumns, a shallow subsoiler follows the Vari-Disc Quad. "There's a financial saving to be made in ploughing less," he adds.

Using Nix as a guide for fixed/machinery costs, the Hardys' reckon on about £28/ha saving where the Vari-Disc Quad is used before drilling and rolling compared with the farm's more traditional approach of plough, cultivate twice (with a Sampo cultivator), drill and roll - see table below.

Time saving is also a factor, says Mr Hardy as the Vari-Disc Quad increases the farm's working window from combine to drilling. "It works best across the line of the combine - avoiding the worst of the straw - and the mixing action is ideal for breaking the soil down at a good speed. We wanted something that would mix the soil well with average horsepower - it's no good having a 250hp tractor in the shed for most of the year," he adds.

This season Mr Hardy has also noticed a reduction in chemical usage for autumn weed control. "One pass with the Vari-Disc Quad produced such a good flush of weeds that we achieved a much better initial hit with the Sting Eco. As far as black grass is concerned the pressure on chemicals to cope with it has been reduced."

For the future, Mr Hard sees the Vari-Disc Quad disc cultivator continuing as an integral part of the farm's cultivation programme, but believes it may work in tandem with a Free-Flow-type reduced tillage drill in a effort to drive cultivation costs down still further.

Article taken from Arable Farming January 29th 2000