Lincoln researchers train apple trees

Press, 12 March 1982, Page 18

Lincoln researchers train apple trees

By

JOHN GOULTER,

journalist, Lincoln College.

Apples might grow on trees, but that doesn't mean they are easy to come by. The need to find alternatives to hand harvesting has concerned New Zealand Agricultural Engineering Institute researchers at Lincoln College for 11 years. Grower interest in the system they have developed for mechanical harvesting, or streamlined hand harvesting, has been high, and some have copied it in their orchards. Now the N.Z.A.E.I. has published a bulletin which tells growers how to grow their trees exactly according to that system — the Lincoln canopy system. It is based on the simple idea of producing apples on a flat plain supported by horizontal wires, rather than on a three dimensional tree. But the two men behind the system, Mr John S. Dunn and Mr Martyn Stolp, were determined” to get it perfected before they widely encouraged its use. “It takes a long time to get things sorted out,” Mr Dunn says. “But we feel we are there now." He says it is

important that specifications for the system are standardised, both within New Zealand and abroad.

Already, about 16,000 trees are being grown under the system in the South Island, and trial work along similar lines is being done in Australia, the United States, Britain, and Europe. It has proved to be more successful than other methods tried overseas, including the "shake and catch” systems on ordinary trees. The machinery needed there was large and costly, and the damage done to trees and fruit unacceptable. In the canopy system, leaders on young trees are trained on to a 1.5 metrehigh horizontal bed of support wires. That plane of wires supports the laterals and gives a uniform flat area for apples to develop, suitable for mechanical harvesting.

The canopy is 2.4 metres wide, with six rows on either side of the central row of trees. With rows of trees four metres apart, there is a gap of just over 1.5 metres be-

tween canopies — enough to walk along comfortably or to allow a tractor or harvester to pass along, with its wheels beneath the canopy. Vigorous growth of laterals has led John Dunn to try out a wider canopy, with an extra wire on either side. If this is successful, the fruiting area would be increased by more than a quarter for little cost. As it stands, the cost for setting up the basic structure is about $4.30 for each tree, or $345 for an 80 tree row. “That’s a high initial cost, but we believe that the efficiency of the system would soon allow growers to see the benefits,” John Dunn says. Canopied Red Delicious trees showed yields starting at 24 tonnes a hectare and steadily increasing to 70 tonnes a hectare over the, seasons from 1974 to 1978. Adjacent centre leader trees

of the same age and variety started out with similar levels but reached a peak of just 58 tonnes a hectare.

A recent refinement to the system which John Dunn believes has improved it a lot is an “H” shape plan for training leaders. Previously several leaders spread out like spokes from the centre, but now just four are trained to run .along the inside wires, forming the outsides of the H, with its crossbar where they emerge from the trunk. From the four leaders, laterals run out across the outer wires, making a grid pattern. This system isolates each side of the tree from the other. One side of the tree can be harvested by an impact method, without having apples fall to the ground on the other side.

The N.Z.A.E.I. has a joint contract , from the Apple and

Pear Marketing Board and the Fruitgrowers' Federation to develop a harvester of the canopy apples for commercial use. According to John Dunn, it will be a light machine with, some form of mechanical impacter. It will be drawn up one side of the canopy at a time, regularly beating the support wires from beneath. A blow to the wires readily removes the ripe apples and, because they are all the same height,

they need fall only a few centimetres on to a conveyor which delivers them to a bin. That way, handling damage is minimal. Even with hand picking though, John Dunn claims that the system offers advantages. Training of the young trees follows a simple pattern, so skilled workers are not needed. The regularly spaced laterals give high light interception and good fruit expo-

sure. The same factor, however, means that hail damage can be higher on canopy trees. There is no general winter pruning, except for occasional replacement of laterals, and the summer pruning can be done with a cutter bar. When it comes to har-. vesting, the canopy is at a good height for hand picking and the system would end itself well to “pick your own” service, Mr Dunn says.