Consistency is key

New Zealand apple growers are maximising profitability by improving fruit quality and uniformity. By Anna Mouton.

“Our goal is consistency of targeted fruit that will pay top dollar,” said Craig Hornblow. He is an AgFirst founder with nearly 40 years of experience in horticulture and a particular interest in high-density apple orchards.

The challenge is that fruit yields and quality vary both within a block and within individual trees. Although our ability to measure and map variability is evolving rapidly, Hornblow pointed out that we shouldn’t become distracted by technology to describe variability.

“At the end of the day, my job is to get in the paddock and chat with the jockey — the orchard manager — about how we can get a better result,” he remarked.

Most growers are aware of the variability contributed by site-specific factors such as microclimate and soil. Mechanical methods to iron out these differences include variable sprayers and spreaders. But Hornblow drew attention to the human factor.

“Every worker who goes in and touches a tree in terms of pruning, picking or thinning influences the orchard with their own personal signature,” he said. “So how can we create consistency in that process?”

Segmentation

Hornblow used the example of an orchard that starts with 600 000 buds, which open into 2 million flowers and set 800 000 fruitlets that are thinned to yield 400 000 apples. At a tree level, a worker would usually have a target of pruning to 300 buds, spray thinning 1 500 flowers, and manually thinning 500 apples so as to pick 200.

“To create better results, I think we need to segment the task even further,” he said. “We need to narrow the focus to improve execution.”

The conventional approach to pruning an old-style tall spindle would be to remove poorly located fruiting branches, remove lateral branches, and renew old fruiting branches. Hornblow advocates segmenting the tree down to the branch level instead. “If we can teach a worker to prune that 35–40-centimetre section, they can prune the whole tree.”

He discussed segmentation in a formal two-dimensional orchard trained on eight wires, of which 6.5 are filled, giving a yield estimate of 75%. Segmentation starts in early winter with the calculation of floral-bud numbers.

“I can then work out my pruning regime,” explained Hornblow. “I can say I want one bud per eight centimetres to give me 400 000 apples per hectare — I can take 100 hectares down to managing an 8-centimetre segment.

“Segmenting each task down to a really tight level allows us to create focus and better execution.”

Segmentation can be adapted to balance the crop load on individual branches to manage return bloom and prevent biennial bearing. Balancing crop load across the entire canopy also promotes fruit uniformity.

Texture

“The second thing I want to focus on around variability is light,” said Hornblow. “If we focus on light, we get a better crunch — better Brix and dry matter in the fruit. That results in a customer who’s satisfied with the great piece of fruit that we’re delivering.”

Light is also crucial for red colour development. “A grower once said to me, if I have fruit colour, I have choices at harvest time. I can pick it today with better pressure and storability or delay and get a little more size,” recalled Hornblow. “But if I’ve got no colour, I’m waiting while quality and storability go downhill day by day.”

He emphasised that more uniform colour development is one benefit of two-dimensional canopies. In three-dimensional canopies, fruit colour tends to worsen, and maturity increases from top to bottom. This leads to harvesting fruit that is either poorly coloured or post-optimally mature.

Labour efficiency is also greater when apples are uniform, so 65%–80% can be picked on day one.

Hornblow considered the question of describing light distribution. Rather than heading into an orchard wielding a light meter, he wants growers to use visual cues to assess canopies.

“My language now is talking about the texture of the canopy,” he elaborated. “Texture is the feel, appearance or consistency of a surface or a substance. It’s a weird word in terms of horticulture, but it refers to the ability to get light evenly through the canopy.”

Three rules

Hornblow has three rules for good canopy texture. “The first one is I want to see through the canopy three to five rows,” he said, “and I need to maintain windows through the canopy.”

When canopies are visually solid, light penetration and fruit quality on the inside suffer. Hornblow observed that we sometimes overestimate how much foliage is required to power fruit development.

“It’s surprising when you look at these trees that are slightly too weak and not filling their canopies. A lot of them are producing the highest volume of target fruit in the orchard,” he said. “We’re growing way too much wood!”

The second rule is maintaining 50% shade — or 50% light, depending on your perspective. Growers should evaluate the quality of the light falling on the ground in the morning or afternoon when the sun’s angle is low and shadows are long.

Dense shadows indicate that light isn’t moving through the entire canopy and doesn’t reach fruit lower down. Large alternating patches of light and shadow point to uneven light distribution throughout the canopy or canopies that aren’t filling in.

Shadows should ideally be evenly dappled. Hornblow noted that this is easier to achieve with two-dimensional than three-dimensional canopies.

For those who like to be technical, he has a third rule: light levels should be 800–1 000 micromoles per square metre per second as measured with a light meter.

“Light is what our business is about,” concluded Hornblow. “We’re harvesting light to generate sugars. If we can get light through the whole canopy for most of the season, we’ll have excellent fruit.”

Watch Hornblow’s presentation on the Hortgro YouTube channel.