Vegetable farmer magazine

Euro Focus


One Dutch beetroot grower has gone to great efforts and expense to ensure its vehicles keep ground damage to an absolute minimum writes Steven Vale.

DUTCH vegetable growers Iwan Schaap and Bart Stam grow roughly a third of the country’s total red beet area of around 360-400ha a year. Operating as Stam-Schaap, all their beetroot is all grown on rented land near company HQ at Ursem – roughly an hour’s drive north of Amsterdam. This generally black soil results in a nice dark-coloured product, but its light nature is not good at supporting heavy vehicles, and over the years the two men have modified many of their machines to reduce the footprint.

This starts at the beginning of the season with the drill tractor. Seed drilled in the tractor wheelings is both later to germinate and harvest. However, their beetroot is drilled on 37.5cm row widths, making it impossible to drive between the rows with narrow tyres or tracks.

After pondering the options, the two men pondered a number of ideas to spread the weight of the drill tractor over a wider area to ensure a level seedbed. They got a local engineering company to implement their ideas, which involved replacing the front axle on their John Deere 6230 with a new front end and a metre-wide tyre. At the rear of the tractor are a pair of Michelin 1050 R 32s – all three tyres of which came from a used self-propelled machine. The result spreads the tractor’s weight exactly over 3m ahead of the 8-row Monosem precision drill. At the end of the six-week drilling season, the front wheel is removed and the tractor is re-united with its standard front axle. Similarly, the wider rear wheels are swapped and the tractor is reunited with its standard tyres.

The novel technology does not end here though, and quite possibly the ‘piece du resistance’ on the machinery side of things is a massive self-propelled two-row bunker-type harvester made by Danish-firm Asa-Lift.

Bought new sometime 2008, the SP240-B is a high-tech machine, which in its current guise probably did not leave its owner with much change from €500,000. Fitted with seven cameras and a sophisticated GPS steering system and, the centrally placed front wheel, which allows the harvester to turn ‘sharply’ at the headland, also features a clever hydraulically-adjusted system to alter the angle of the front wheel. Providing around 70cm of play, this is useful when opening up a field, allowing the operator to set the two sets of lifting shares to accurately take out the crops rows between the tramlines. The empty weight of the giant vehicle of around 18 tonnes increases significantly with a full 6-tonne bunker – which incidentally is emptied in just 45 seconds. The grower was pleased with the first season’s performance, but concerned as to the damage this harvesting heavyweight could do to the land.

During the 2008/2009 winter they took the decision to swap the wheels for three rubber tracks made by Dutch engineering company Westtrack (Now Zuidberg Tracks). The machine’s standard wheels have never been used since, and the grower is very pleased with the in-field performance of the three 76cm-wide tracks, which even in the wet leave barely a mark. The downside to tracks, however, is rubber and tarmac is not a good combination on the road, and while the grower looks for land as close to Ursem as possible, the harvester is still required to travel many kilometres.

The two men appear to have come up with a novel way to extend track life. A 500lit water tank secured to one side of the harvester not only supplies water to one of the sieves, but also to nozzles located on the underside of each track. The two men reckon spraying water onto the inside of the track during road transport helps to cool the rubber. It appears to work. The two rear tracks are now at the end of their life and will be replaced this winter, but these are the same versions fitted to the machine six years ago.

Harvesting normally begins at the end of June and continues until sometime at the beginning of November. Beetroot lifted during the early part of the season is sold directly for the fresh market, (25% under contract) with the main storage season starting around 10 September. Average yields vary from 70 to 90t/ha, and during this main season the harvester works non-stop from 6am to 22pm. “Operating at speeds of 3.5-5kph we usually cover 2.5ha/day during the busy season,” says operator Bart Vet.

After seven seasons of use, the harvesters good looks are put down to a thorough maintenance programme, which sees the self-propelled harvester pulled apart each winter. All wearing parts and bearings are replaced, and the grower is hoping the harvester will go on to successfully clock up another 6,000 hours.

Auto tyre inflation

The water nozzles help to keep cool the harvester’s rubber tracks on the road, but it is not just the self-propelled machine that is frequently required to hit the road.

All Stam-Schaap’s tractors and trailers spend quite a bit of time on the road, and all are fitted with a central tyre inflation system. Take the drill tractor, for example. In the field, the pressure of all three tyres is quickly lowered to 0.4 bar. With a capacity of 500lit/min, the compressor takes just a couple of minutes to inflate the tyres to 1.5 bar for road travel. Similar systems are fitted to the rear wheels of the rest of the grower’s John Deere tractors.

The grower has three identical Beco-made Super 2400 tri-axle trailers. With a capacity of 24 tonnes, all six tyres on each trailer are also fitted with a tyre inflation system. With an output of 3,000lit/min, the pressures of all six tyres is quickly altered from 1.1 bar in the field to 3-3.5 bar on the road.


  1. This is believed to be the only Asa-Lift SP240B on rubber tracks in the Netherlands.
  2. This tank supplies water to nozzles located on the underside of the three rubbers tracks to help keep them cool on the road.
  3. The harvester’s two rear tracks have lasted six seasons. They will be swapped for new belts this winter.
  4. The Dutch grower is pleased with the rubber tracks, which barely leave an indentation on the land.
  5. Stam-Schaap has three identical Beco-made tri-axle trailers. Each one carry’s 24 tonnes at a time.
  6. The central inflation quickly alters the pressure of each trailer tyre from 1.1 bar in the field to 3-3.5 bar on the road.
  7. The hydraulically-tilting trailer body not only allows the harvester to reach over the side to empty its bunker, but also helps to reduce the fall height.
  8. All the grower’s John Deere tractors – including this 7530 – are fitted with a central tyre inflation system.
  9. Stam-Schaap grows roughly a third of the total Dutch red beet area of around 360-400ha a year.
  10. Operator Bart Vet says the Asa-Lift harvester covers around 2.5ha/day during the busy season.
  11. The drill tractor is modified to run on three 1m-wide tyres. This helps to spread the footprint over the same width as the drill – namely 3m.