When Pierre-Olivier Dion-Labrie took over as chief winemaker at the historic Château de Châtagneréaz vineyard in 2013, he found there were no records of the soil types beneath the 20 hectares of grapevines looking out over Lac Léman.
Soil type can have a considerable effect on the growth of the vines and the subsequent quality of the grapes they produce so he decided to conduct a soil survey of the estate. Having studied at Switzerland’s premier viticulture college Changins in nearby Nyon, which also provides consulting services to wineries, he approached his old teachers for a solution.
The university carried out manual probing of the ground across 13.4 hectares of the vineyard, discovering 16 different soil types, but while the broad distribution of each was known the frontiers between soil types were vague and the effect each was having on the vines was largely unknown.
Researchers at Changin suggested using drones to gather aerial imagery that would allow them to map these frontiers far more accurately, quickly and cheaply. The agreement benefitted both parties as it gave the vineyard access to high resolution aerial imagery, while it allowed the university to test its theories and techniques for using drones for precision viticulture.
“I studied there so I knew the faculty are at the top of their game,” he says. “On their side it was an opportunity to use our estate as a big playground to continue improving their techniques with the drones.”
The vineyard and the university partnered with Swiss drone manufacturer SenseFly which was interested in testing how its fixed-wing eBee unmanned aerial vehicle (UAV) could be applied to viticulture.
Switzerland’s relaxed drone regulations mean that there were no legal barriers to flying. UAVs under 30kg that are insured and operated within line of sight, below an altitude of 150m and no closer than 5km to an airport or 100m from crowds require no registration.
Using the drone’s automated flight planning software, researchers from Changin began to fly over the vineyard from February 2014. The students collected a variety of data including standard aerial photographs, oblique imagery and near-infrared (NIR) images. This data was then used to create 2D orthomosaics and 3D models using senseFly’s Terra post-flight image processing software.
Of particular usefulness was the drone’s ability to produce normalized difference vegetation index (NDVI) imagery, which Dion-Labrie had been introduced to while working at a high altitude vineyard in the Argentinian wine region of Salta prior to taking over at Châtagneréaz.
Developed by Nasa in the 1970s, the technique relies on the fact that plants are unable to use NIR light for photosynthesis so their leaves reflect these wavelengths to prevent them from drying out. A higher NIR reading means more leaves and therefore better plant growth.
In Argentina Dion-Labrie had been using NDVI imagery captured from a plane for two very specific purposes – to carry out water studies as well as track the damage done to vines by leaf eating ants – but this time it was used to build up the first comprehensive picture of the Châtagneréaz estate.
“In Argentina we needed very precise information, whereas now we needed to start from scratch,” he says. “There was really very little information about the soil. All we had was the year of plantation and the root stock.”
The NDVI imagery gave Dion-Labrie a high resolution picture of the vigour of vines across the estate and when married with the soil survey data this enabled him to fine tune the frontiers of the various soil types, which will have a major impact on how different parts of the estate are managed.
“The drones were the fastest and most precise way to get high quality pictures that enable us to most clearly define the frontiers between distinct soil types by observing the effect on the vines,” he says. “In that sense, an aerial image is the best and by using a drone getting those pictures was much easier to organise and cheaper than planes would have been.”
While mapping the estate’s soil types was the primary motivation for the project, the data gathered on growth rates and the vigour of the vines has had additional useful applications as well.
While a lay person would assume that all farmers would want their plants to be as vigorous as possible, for vineyards high growth rates are not always a good thing. If a vine’s growth is too vigorous it can hinder the ripening of the grapes, not least because a dense canopy prevents the sun from falling on the fruits.
“Using the drone data we were able to pinpoint some zones where the vigour was obviously higher than we wanted it to be, so we took them out of our fertiliser program,” says Dion-Labrie. “On an environmental basis it was a benefit and also from the economic view because we saved fertiliser.”
Hailstorms can cause massive damage to both grape crops and the vines themselves, and though there hasn’t been a hailstorm in the region since 2013, Dion-Labrie says rapid inspection after the event could be another useful application for drones in the future.
“If we had hailstorm damage I would probably call Changin to fly over the estate to really get a global picture of what is going on,” he says. “That would be a very good application for drones, because if the weather is nice I can call them and they will come in under 24 hours. A plane could take days to organise.”
Dion-Labrie believes that Changin has only just begun to scratch the surface of the potential for drones in viticulture, but while he is open to suggestions he says that researchers and drone companies need to remember that commercial organisations like his need an airtight business case before they can justify participating.
“We can’t afford to conduct a study just for the sake of it. When I go to my board and ask for money for such things I have to come up with really pragmatic, really practical information on what good it will do. Otherwise I probably won’t get the funds,” he says.
So far the drones have proved useful enough for Dion-Labrie to enter into a commercial agreement with the university. He allows Changin to fly over his estate for research purposes for free, but he also pays for regular surveys, the latest of which will take place this week.
“We learned that drones, if used properly can be an extremely powerful tool for agriculture,” he says. “But you have to know why you fly them. Gathering information just for the sake of it is pointless. You have to know what you are looking for before flying it.”