5 September 1997

New kit to suit wide beds

Switching to an extra-wide potato bed system demanded a new fleet of machinery on one Essex unit. Peter Hill reports

WHEN Essex potato grower Jim Padfield and son Charles adopted a system based on beds containing three full width rows new equipment was clearly needed.

The beds are 2750mm (108in) across, demanding extra wide tractor wheel tracks, a stone/clod separator half as wide again as a standard model, and a suitably dimensioned potato planter.

A harvester capable of lifting the three-row beds, as well as the two-row beds which are installed every 25m (82ft) to provide tramlines for spraying and irrigation, was also needed.

"Although the system was extensively trialled by the Scottish Centre of Agricultural Engin-eering, no one had tried the system commercially as far as we know," says Jim Padfield. "Our only option was to modify or build suitable equipment from scratch."

Higher yields and more efficient use of nutrients and irrigation water thanks to fewer wheelings and soil compaction are the main goals of the wide beds. Wheelings fall from 25% to just 17% of the growing area and SCAE trials gave a 14% mean yield increase for the centre row of the beds over three years. That gave a 6% increase in marketable yield overall.

After ploughing the boulder clay, beds are marked out in the autumn using a home-built former, then sprayed off during the winter before final bed formation witha stone/clod separator in thespring.

More of a challenge

The stone/clod separator and three-row planter posed more of a challenge. Suffolk vegetable harvester specialist Reed & Upton made the chassis of the 1500mm (60in) Pearson Megastar separator half as wide again, while a local engineer made new high-tensile steel shafts for the star rollers.

The planter was produced in the farm workshop from a Gruse three-row narrow bed planter by repositioning the outer planting units and widening the hopper.

"All the equipment worked well first time out, which was just as well because having decided to try the wide bed system we had to commit all our potatoes to it," says Charles Padfield.

The remaining consideration was how to harvest the crop. A self-propelled harvester was favoured for greater output, easier manoeuvrability in tight fields and better traction in difficult conditions. Dutch firm Amac produced a completed machine in barely nine months.

Faster Harvesing

"Assuming there is no change in forward speed, moving from two- to three-row lifting immediately gives you a 50% increase in work rate," notes Charles Padfield. "But you also have fewer headland turns, so the overall improvement is probably nearer 60-70%."

To make the most of that potential, the harvester has a reversible elevator so the crop can be windrowed during trailer changeovers – and also to open-up fields.

The Amac has diablos that can be adjusted hydraulically to match the three-row crop beds and two-row tramline beds.

"We dont have any potatoes grown in conventional beds for comparison so we cant quote figures for yield improvement," says Jim Padfield. "But it was obvious in last years crops that the centre rows of each bed had taller, fuller foliage and produced a lot more tubers, albeit smaller in size than in the adjoining rows."

For this years 182ha (450-acre) crop of Nadine, Desiree, Pentland Dell and Ambo, the centre row seed rate was cut by 11% which, test digs suggest, has stabilised tuber size.

Jim Padfield watches as the purpose-built Amac harvester gets to grips with the three-row beds last year. Higher yields and less inputs are claimed.

Field preparation (including spraying off weeds in this case) needs tractor wheels set at 2750mm (108in) centres. This was achieved using bar-type rear axles and "cotton reel" spacers on the front (inset).