Welcome to the digital orchard

As part of an international project, Corelli Grappadelli has been developing a quicker way to estimate photosynthesis using a mathematical model based on leaf temperature and fluorescence. While here, he collected data to test the model, which, if successful, will enable Dzikiti to measure photosynthesis in 30 seconds.

New canopies reshape light interception

Conventional horticultural wisdom is that maximising light interception maximises yields. Corelli Grappadelli disagrees. "With our work on peaches, we demonstrated that photo-inhibition under high light intensities costs you about 10% photosynthetic carbon every day."

High light intensities damage proteins involved in photosynthesis. The tree continually replaces the damaged proteins – using resources that could have been allocated to fruit production.

"Because of all that light, leaves will also be much warmer, so the tree needs more water to cool them," adds Corelli Grappadelli.
He conducted shade-net trials in apple orchards showing that a 50% reduction in light led to a 50% saving in irrigation water without any yield or quality losses. However, he cautions against limiting light as aggressively in peaches, where excessive shading can reduce fruit size and sugar content.

Corelli Grappadelli is excited about the planar cordon systems developed in New Zealand. He speculates that the impressive productivity of these systems might be due to high light interception combined with light filtering and scattering by the canopy.

"In these systems, you intercept a lot of light, but very few leaves are under very heavy photo pressure at any time of day," he comments. "These new types of canopies are going to change the picture."

Photovoltaics for the triple-win

Corelli Grappadelli has been looking into shading trees for about 20 years. "Early on, someone in my lab said, wouldn't it be nice if we could turn the light we don’t use into electricity."

Having tried photovoltaic plastics without success, Corelli Grappadelli has embarked on pilot projects funded by utility companies to assess photovoltaic panels in apple and kiwifruit orchards.

"Ecophysiologists are needed to certify that the shading doesn't hurt production, because, in Europe, crop growth wins over electricity generation," he says. "But I don't see any problems with that. I can't wait to start collecting data to show how mutually beneficial this is."

Corelli Grappadelli describes photovoltaic panels over orchards as a triple-win situation. Producers win by optimising light conditions for their trees while also accessing electricity that can power existing equipment, like irrigation pumps, and new technologies, like electric rovers.

"Of course, the utility company wins – they talk about one Megawatt for every 1.5 hectares," says Corelli Grappadelli. "And society will win because of less water and fossil-fuel use, and reduced carbon emissions. I expect a revolution to come out of this."

As is true in SA, the move to renewables in Italy must overcome regulatory obstacles. During the past 18 months, Italian legislation changed to allow apple growers to generate electricity while remaining eligible for agricultural support programmes. Previously, apple growers were no longer considered apple growers when their income from electricity generation equalled their farming income.

However, due to aesthetic concerns, certain regions of Italy still restrict the area that a grower can cover in photovoltaic panels. But Corelli Grappadelli is confident that the realities of the global energy crisis and climate change will boost the political drive to adopt renewables.

Ecophysiologists and engineers team up

The University of Bologna lies in the so-called Motor Valley of Italy, home to icons such as Ducati, Ferrari, Lamborghini and Maserati, and the Imola Circuit, which hosts the Italian Formula 1 Grand Prix. Corelli Grappadelli explains that this gives him unequalled access to engineering excellence.

He is collaborating with engineers on everything from developing an electronic leaf that can give accurate photosynthetic readings to designing smart implements for autonomous rovers. For example, he would like to see rovers equipped with tools to precision-thin flowers.
"I asked the engineers if they could do this with a laser, and the answer was, of course we can – although we still need to work on flower recognition in clusters," says Corelli Grappadelli. "What is a tall order for us is a lot more achievable for engineers."

Another technological innovation is creating digital representations – digital twins – of real-life orchards to aid precision management. Corelli Grappadelli can imagine a future where electric rovers gather data in the orchard to construct the digital twin that provides feedback on which flowers to thin or which fruits to harvest.

People might still do the work, but they could wear headsets that, for example, virtually mark which fruits to pick or which branches to prune.

"I see a digital orchard emerging in the near future," says Corelli Grappadelli. "It will not be 100% robotic immediately, but eventually, we will be forced to replace human beings because it's hard to bring people to work in the orchard."

Fortunately, the expertise to develop autonomous electric solutions is available close to home. "I call myself lucky," he reflects. 'I can sit down two or three times a year with two or three different teams of engineers who have discovered agriculture and fruit-growing."