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202103 Fresh Quarterly Issue 12 07 Oak Valley
Issue TwelveMarch 2021

Oak Valley

Growing greener Grannies. By Anna Mouton.

“Granny Smith is a very high value apple,” says Graeme Krige, technical adviser at Fruitmax Agri, “but it has to be perfectly green or it’s out. It’s not the case that mild sunburn is okay.” Research has shown that nets reduce sunburn — but nets also promote vegetative growth at the expense of fruit production.

The Orchard of the Future at Oak Valley, Elgin, had two objectives, according to Krige. “One was to see if we can grow Granny Smith commercially with nets. The other was to see if we can grow an orchard at higher densities than normal.” Both these objectives depended on using a semi-dwarfing rootstock.

A small start

The one-hectare trial orchard was planted in 2012 with Granny Smith on the semi-dwarfing G.222 rootstock. Unfortunately the nursery trees were only 0.5–1.2 metres tall. “I think the trees were small because G.222 was relatively new at the time,” recalls Krige. “The nurseries were still learning and G.222 was difficult to root.”

The little trees established well. “I believe that young trees benefit from a net,” says Neville van Buuren, pome-fruit production manager at Oak Valley Estate. But the first year of the trial was effectively spent growing nursery trees rather than growing an orchard. This compromised one of the key targets for the Orchard of the Future programme — to reach a cumulative production of 300 tonnes per hectare by the sixth leaf.

“We started harvesting a year later than we would have,” says Krige. The first harvest totalled 15 tonnes per hectare and the cumulative total in sixth leaf was 291 tonnes. Not too bad considering the unimpressive starting material. The orchard produced a bumper 123 tonnes per hectare in seventh leaf, suggesting that it would easily have met the 300-tonne target if larger trees had been planted.

202103 Fresh Quarterly Issue 12 07 Oak Valley Figure

Losing a year due to poor tree quality is a big deal when planting at high density because all those extra trees cost money. And then there’s the price of the shade-net. The impact of delayed production is exacerbated when cumulative interest is factored in. In a high-density orchard, time literally is money.

However, the Orchard of the Future at Oak Valley has outgrown its teething problems. “The orchard is very profitable,” attests Krige. “It’s currently in the top ten orchards in our group, across all cultivars.”

The net result

“There were a lot of net trials on Grannies in the past, on older rootstocks, and they were a disaster,” says Krige. “The trees become too vigorous. So we knew that we needed a rootstock that imparts more reproductive behaviour and controls vigour.”

The orchard was initially covered with a white 20% shade-net, and the sides were closed with white 40% shade-net. It was hoped that covering the sides would help to exclude pests such as codling moth, which proved possible, but created other problems. Temperature and humidity were greater in the net-enclosed orchard than outside.

“The first three crops had very poor pack-outs,” remembers Van Buuren. “It was disappointing.” The fruit were yellow rather than green and suffered severe sunburn. A combination of hot weather and drought didn’t help. Following the poor fruit quality of the 2017 harvest, the side nets were removed. Fruit quality subsequently improved significantly, and the orchard cull percentage more than halved the following year.

Krige points out that previous trials with nets were conducted on mature trees with large canopies. “We chose a white net because it has a long life and it’s less expensive. But we’ve realised that, with trees that are still filling their space, a white net doesn’t block enough sun for a Granny.” In future, he would start with a grey net, perhaps replacing it with a white net once it wears out.

The shade-net in this Orchard of the Future was a fixed net. Krige and Van Buuren agree that retractable nets are their preferred option going forward. Retractable nets have many advantages, including bee-friendliness, although pollination was not a problem in this trial.

Retractable nets can be opened after harvest to give the trees maximum light for the rest of the season, and beyond. “You also get the benefit of exposing the trees to proper winter cold. Because it always remains warmer under the net, even in the dead of winter,” says Van Buuren.

Success with Granny Smith under nets was possible thanks to the semi-dwarfing G.222 rootstock. The trees have gone from strength to strength, according to Krige. “There’s not been a year, touch wood, where we’ve seen them alternate. They’re full of flowers every year, even with a net that doesn’t open.”

Easy pickings

Granny Smith on G.222 proved to be both precocious, bearing 15 tonnes per hectare in what was effectively the second leaf, and productive, bearing 123 tonnes in 2020, which was effectively the seventh leaf. Fruit size and quality under nets has been excellent. But high-density plantings offer more than just great harvests.

“The trees pick super-easily,” comments Van Buuren. “The orchard picks better than our conventional old Granny Smith orchards. It’s simple and open, and has a lot of nice big fruit on it, so the bins fill quickly. People love picking an orchard like that.”

Van Buuren notes that the orchard has also become simpler to prune as it ages. “We struggled to get a tree initially, due to the poor material that was planted. But the trees handle very easily at the moment.”

“If we had to redo it, we would have planted it a little more densely,” says Krige. “We would have created an even simpler canopy and it would be even more labour-efficient. We still have semi-permanent branches, which we don’t think is the right thing to do in future. So although pruning is a lot easier already, it will become even more so.”

Semi-dwarfing rootstocks are not entirely cost- and labour-saving. The trees require more robust trellising systems than trees on more vigorous rootstocks. “We have to beef up the trellising system with dwarfing rootstocks otherwise the trees fall over,” says Krige. “And one thing we learnt was that G.222 is prone to breaking at the graft union. The trees must be tied in well from day one.”

Looking to the future

The Orchard of the Future at Oak Valley faced challenges, but Van Buuren has no regrets about the programme. “It’s the best money ever spent. Just because you didn’t do everything right, doesn’t mean you didn’t learn from it. We learnt a huge amount — about what not to do.”

Krige is quick to point out that the orchard is a commercial success. He stresses the importance of planting commercial-scale trial orchards to test new concepts. “You can’t make recommendations to growers, on cultivars or rootstocks or training systems, based on five trees. You need someone to spend the time and money to plant a hectare, to see how it works.”

New plantings at Oak Valley will adopt the principles of the Orchard of the Future, but strive for further improvements. “We’re planting Grannies again next year,” says Van Buuren, “and with a net, but it’s not white. And the trees are on a different rootstock with a different training system.”

High-density is here to stay, Van Buuren emphasises. “Not a single orchard on this farm was planted wider than 3.5 metres last year or this year. That’s the future. Four metres is old news.”

Krige agrees. “When the Orchard of the Future was planted, 99% of the orchards planted that year were at 4 by 1.5 metres. We no longer order nursery trees to plant at 4 by 1.5 metres.”

Krige does have one quibble with the Orchard of the Future programme. He takes issue with the name. “If you want to be innovative, you should get up every morning and go through the orchards, and think, what did I do yesterday and how can I improve today? You can’t call something the Orchard of the Future, because you need to continuously strive for improvement.”

Image: Neville van Buuren — left — and Graeme Krige.

Supplied by Anna Mouton.

Summary

Table 1 The Oak Valley Orchard of the Future at a glance

Year established 2012
Rootstock G.222
Scion Granny Smith
Cross-pollinator Rosy Glow
Spacing 3.5 x 1.2 metres
Training Solaxe
Size 1 hectare
Trees per hectare 2381
Nets 20% white fixed

The orchard team

Daan Brink

Ernst Heydenreich

Graeme Krige

Neville van Buuren

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