4 September 1998

Right settings essential to cut potato damage

The way potato harvesters

are set-up and operated has

a fundamental influence on

tuber damage. Peter Hill

asked manufacturers for

their top tips

POTATO harvester settings need to take account of a number of factors, including soil type, soil conditions, variety and yield.

But whatever the settings needed to cope with these factors, they need also to be always tuned to posing the minimum risk to tuber condition.

"Operators have to think about what they are doing before they get around to setting up the harvester," says Standens Andy Reedman. "Check that the correct tractor and harvester wheel settings for the bed dimensions are being used, and that the tyres are not so wide as to squeeze the ridges and cause bruising before the potatoes have even seen the harvester."

The same goes for the intake discs and depth control diabolos, says Barry Burrell of Grimme.

"Use discs at the wrong setting and you get cut potatoes; and the same applies to poorly set share depth," he says.

Share angle also has an influence, particularly as on bruising, says Kvernelands Tim Needham.

"Ideally, an imaginary line extended from the face of the share should intercept the nose of the primary web about 5mm from the top," he advises. "Set too low and the potatoes bump into the web; set too high and the flow of crop and soil off the share is impaired."

Working through the harvester brings the operator to web settings. "Where the angle is adjustable, use the shallowest setting compatible with the need to remove soil so that tuber roll-back is minimised," says Mr Burrell. "And at this point we need to turn down the agitation as far as possible."

On the latest Grimme GZ, an adjustable "wavy web" arrangement is used instead of conventional agitation and this too should be set to the least aggressive setting that is feasible for the conditions.

Haulm rollers represent one of the main sources of bruising. It can be a difficult balance to achieve, given that some varieties produce more top than others, are more susceptible to bruising than others (susceptibility varying according to dry matter content), and may hang on to the haulm more vigorously.

"Set haulm rollers to a more severe setting than necessary and they tend to whip the haulm away with any tubers tangled in it or still attached getting a bit of a bashing," notes Mr Reedman. "Tuck the roller away and rely on the haulm guide rollers as far as possible; on the Statesman, it just takes a few turns of a hand-wheel to make the adjustment."

But to minimise the amount of haulm taken in with the crop, he says, get rid of it in the first place by using a tractor-mounted flail topper with side conveyor.

Cleaning systems also have the potential to harm tubers if not adjusted to suit conditions and operating speed. Again, it is a case of finding the least aggressive settings for what needs to be achieved.

"With contra-rotation rollers, like the Dahlmann system, speed and angle adjustment are the two main concerns," says Tim Needham of Kverneland.

"Set the speed so the potatoes are just bubbling not bouncing too high, and set the angle so the crop keeps moving across the rollers without getting pinched, but not so fast that they may be bruised on landing in the elevator."

Water sprays can lubricate the rubber roller surface and avoid excessive pinching damage in dry conditions, says Mr Burrell.

The elevator also needs to be correctly tuned – fast enough to carry the crop away effectively but not so fast that tubers can rattle around in pockets only partially full. And elevator height has a big influence on bruising.

"It really has to be kept as close as possible to the trailer floor or crop to minimise the drop height," Tim Needham advises. "Trailer floor pads give the first potatoes loaded a softer landing, and fall breakers attached to the elevator can also help, although the danger is that the operator comes to rely on this and uses high elevator settings."

With this multitude of settings in place, working speed remains the key influence on harvester performance and damage levels.

"The aim must be to keep the machine full so that tubers do not have room to rattle about," says Mr Reedman. "At the same time, it does not want to be so full as to have potatoes pushed up against web side panels, getting rubbed and scuffed as they pass through the harvester." &#42

TOP TIPS FOR LOW TUBER DAMAGE

l Use correct wheel track settings for the beds being lifted.

2 Use the narrowest tyres feasible for the tractor.

3 Remove haulm using flail topper/conveyor.

4 Set correct share angle.

5 Use correct side disc width and share depth settings.

6 Use the least web agitation possible.

7 Adjust haulm rollers to be as least aggressive as possible.

8 Set working speed to keep a cushion of soil for as long as possible.

9 Set contra-rotation cleaning roller speed and angle to least aggressive

settings possible.

10 Adjust elevator speed to keep pockets comfortably full.

11 Adjust elevator height as close to trailer deck and crop as possible.

12 Use an elevator fall-breaker and/or trailer floor cushion.