8 September 2001

10

tips to fewer losses

Heres how to set up your potato harvester to minimise damage to the crop and avoid volunteers

THERES always going to be an element of compromise in harvester set-up between timeliness of lifting, allowances for field conditions and economical operation. There are also basic requirements for set-up on which the grower need not compromise.

The value of getting harvester settings right is well illustrated by the potential consequences of failure. Cut or damaged potatoes can easily lose an expected pre-pack premium and wipe thousands of pounds in value off a badly-harvested field. Over-the-harvester losses of tubers can result in an average 12 volunteers/sq m in the following cereal crop. If sugar beet is included in the rotation, just five volunteer potato plants/sq m can knock beet yields back by 16t/ha (6.5t/acre).

Fraser Milne, of the Scottish Agricultural College, has produced a list of 10 priority items the grower or harvester operator should attend to when harvesting. These are aimed at minimising damage or losses without compromise to field and crop conditions.

Manufacturers handbooks will contain many recommended settings that should be followed for individual machines. Basic set-up needs to be right from the outset, with the machine level, the wheels aligned correctly, and hitched with the correct height of drawbar and extension length to allow turning. The harvester should have a width of share adequate for the drill profile and bed widths being lifted.

The front end should be set to avoid both spillage of tubers and to avoid taking in too much soil and stones from the windrow. Discs set too deep will carry the weight of the shares, and too wide will mean excessive intake of soil. The diabolo rollers on harvesters hold the drill together as the shares enter underneath and also regulate the depth of the share.

Correct alignment with the drills is important, as is downward pressure. Too much damages tubers close to the surface and can cause tubers to spill out over the side in some soil types and be sliced by the discs. Some machines have electronic control to regulate pressure or "off-loading units" can be used.

Spillage can be minimised too with properly adjusted crop retainers to suit the row widths. Avoid small gaps around the share to web transfer area where tubers can be lost.

Recommends

On the primary web itself, Fraser Milne recommends keeping agitation off whenever possible unless increased soil separation is required. He suggests a typical web speed to forward speed ratio of 1.1:1 on wet sticky soils and 0.7:1 on lighter soils. Excess side web movement will lead to tuber damage so guide rollers should be kept tight on to webs, and a regular check made for damaged rods, bad joining links and web attachment plates. To avoid roll back of tubers, soil should be kept on the web right to the top or it should be crowded with tubers.

Clod breakers, haulm rakes and spreader fingers are extras he believes are best avoided because of their potential for causing damage. Haulm rollers are a major source of tuber damage, and he believes a suitable compromise between crop and haulm removal is to set the roller to remove 70-80% of the haulm at this point. The further forward the roller is underneath the primary web head roller, the less haulm is taken out and tuber damage is lower. Haulm fingers to guide haulm into the haulm extraction rollers should be well lined with rubber and spacing to the web adjusted for the amount of haulm present.

On the second web, covers can keep damage down. Aim to run the web around 85% filled with tubers, and keep speed low enough to reduce impact damage and fast enough to avoid tubers piling up and being caught by the haulm roller.

The different types of cleaning units used by manufacturers should be set for crop and conditions after referring to the makers handbook. Watch out for stuck stones, wear, large vertical drops and gaps, and keep flow smooth. Padding and side curtains should be monitored for wear on the picking tables, and conveyor speeds kept low to keep tuber speeds down.

All elevator rods should be rubber-covered and side gaps minimised to avoid tuber damage. Drop heights and speeds should be kept low so flights are 75% full. Operator skill is important during the harvester to trailer transfer when potatoes are typically dropping 1-2m on to a hard surface. Trailer mats, fall breakers and elevator height control devices all make the task easier for the driver.