30 November 1984 Intensive apple growing returns are investigated

Intensive apple growing returns more profit than semi-intensive growing, trials at Lincoln College have shown, but final yield difference when all trees are mature is not yet known.

Three varieties of apples have been grown intensively and semi-intensively in a college research orchard since 1977.

Yields of the three varieties, Granny Smith, Royal Gala and Cox's Orange, from the two growing methods have been compared over six harvests.

Average yields of Royal Gala and Granny Smith were higher on all intensive plots than the average on the best semi-intensive plot.

Results for Cox's Orange are much the same, but the best semi-intensive plot is now yielding as well as some intensive plots.

However, the accumulated marketable yield over the six harvests puts the intensively-grown apples well ahead.

Accumulated yield a hectare for the best plot of semi-intensively-grown apples of all three varieties is only about two-thirds of the average yield of these apples grown intensively.

Intensively-grown apple trees bear fruit very early in growth, do not grow more than three-metres high and are easier to prune and spray.

Until now the trees in the trials have yielded much better than the semi-intensive trees, but this may not hold over the life of the trees.

But intensive trees cost more to establish than semi-intensive trees, because of the extra trees needed, and because a stake or wire is needed to support each tree.

Support is needed because intensive growing uses dwarfing M9 rootstock, weaker than the MM106 rootstock used in semi-intensive growing.

Trees on dwarfing M9 rootstock, sometimes called spindlebushes, are very popular and successful in Europe.

These trees are planted at 1500-2000 to a hectare about 1.5 metres apart and with 3.5 metres between rows.

The three cultivars used in the trial were planted in 1977 with four main plots for each system.

Plots planted with M9 rootstocks had 1905 trees to the hectare, while those on MM106 rootstock were planted at about 635 trees to the hectare.

All the trees were planted where apple trees had grown before, and the trial has shown M9 as tolerant to any resultant root disorders.

No M9 trees died or showed any sign of root disease during the trial.

But one-fifth of the MM106 trees have died or are showing symptoms of disease.

The MM106 trees were all on virus tested rootstock and so did not sustain any virus.

Although the M9 trees have not sustained root disease, some virus has shown on these.

Apple mosaic showed on all three cultivars, and there was a one-to five per cent russet ring on the Royal Gala.

The Reader in Horticulture at Lincoln College, Dr David Jackson, said that unfortunately when the trial was established virus-tested M9 rootstock was not available.

Had virus-free trees been used the M9 might have done even better, he said.

Quality and size of the fruit was much the same from both growing systems, and in a two-year trial the fruit stored equally well.

Four Lincoln Staff two from plant science and two from horticulture have been involved in the trial.

They are horticultural research technician Mr Gilbert Wells, plant scientist Mr Dick Lucas, who is senior lecturer in experimentation, tutor in field technology Mr Bill Nagle and Dr Jackson, who is a horticultural scientist.

Dr Jackson said they had all been impressed by the crops from the M9 trees, and the ease of pruning, spraying and harvesting because no ladders had to be used. "We are all surprised that growers have not taken to the intensive system, and one reason could be that M9 apples are thought not to store as well as those from more vigorous trees, but trials have shown this not to be true.

"Quality, size and storage are all about the same."

Dr Jackson said with most fruit crops there was a move to short-term cropping for an early return on investment, so intensive growing was ideal.

Growers could quickly build up production when new clones or cultivars were available, and if these were not economic move into others, he said ends.

Further information from Dr David Jackson, Reader in Horticulture, Lincoln College, Canterbury, New Zealand.