It's a beautiful summer's afternoon as I arrive at the Chapel Down winery in Tenterden, Kent. Fortunately it's a weekday, so things are relatively quiet. At the weekends it is heaving with visitors keen to sample some of the UK's most celebrated wines. They're eager to buy, too: last year the tasting room sold over £1m worth of wine. In contrast to the rather homespun reputation of English wine, Chapel Down is a very professional operation. As well as the winery and tasting room, there's a restaurant and walking routes through the vines are signposted. And the vines? They're looking beautiful: the canopies a vivid green, with spindly growing tips and tendrils grasping towards the cloudless sky.
It's early July. Flowering – a little early this year – has just finished, and baby grapes are just beginning to form. After two difficult harvests, things look set for a bumper crop in 2014, as long as nature plays fair until October when the grapes will be picked. But as Richard Lewis, the vineyard manager, tells me, there's more to grape growing than hoping for good weather. With some 65 hectares of vineyards (about 91 football pitches in size) to manage, Lewis believes technology is a necessity. And he's not alone. "Precision viticulture" looks set to change the way UK vineyards are managed, forever.
The UK wine scene is at a very interesting stage. Many commentators suggest that it's about to hit the big time. Back in the mid-1980s grape growing here was largely a hobby industry, with 281 (mostly tiny) vineyards growing covering 430ha of land in total. There was a burst of plantings in the mid-1990s, which took the area under vine over 1,000ha, with a slight increase in the number of vineyards to 435. Since then, after a bit of a hiccup in the early noughties, the area of vineyards has increased to over 1,400ha, with the number of vineyards and wineries decreasing slightly. The full story isn't told in these figures, though: there are significant vineyards that have been planted but which aren't yet in production. Climate change has certainly helped. The UK is right at the climatic margins of where it is possible to ripen wine grapes, and even the small increase in average temperatures over the last few decades have been significant for viticulture.
The catalyst for this growth has been a boom in English sparkling wine production. Our cool climate produces grapes with naturally high acidity and low sugar levels. This combination can make for challengingly tart table wines, but it's ideal for making top quality fizz. We also have lots of chalky soils, similar to the famous vineyards of Champagne, although these aren't the only soils that are capable of making really good sparkling wine. There are now several large, ambitious sparkling wine producers in the UK whose wines are getting a lot of positive press: Nyetimber, Ridgeview Wine Estate, Gusbourne Estate, Camel Valley Vineyard, Hambledon Vineyards and Chapel Down. Add in some small, premium producers such as Hush Heath Estate and Coates & Seely, and things begin to get quite interesting. There's also a super-ambitious newcomer, Rathfinny Estate, which is on the way to planting 160ha of vines, with a focus on sparkling, although they have yet to make any wine. The UK wine industry is entering a new, more professional, more serious phase, and sparkling wine is leading the way.
It's against this backdrop of increasing professionalisation that the new technology of precision viticulture (known in the trade by the initials, PV) is beginning to be employed, with the potential of improving wine quality by helping vineyards yield better quality grapes. PV is a branch of precision agriculture, a relatively recent development in farming that first emerged in the early 1990s. Its basis is that nature is uneven. Traditionally, farmers have ignored the natural variation in their fields, and have treated them uniformly. But over the last couple of decades affordable technologies have been developed that allow farmers to make accurate maps of this natural variation and then manage their fields accordingly. For example, some bits might need more fertiliser, others less. Or the soil properties might vary in such a way that certain parts will need irrigating while others won't. It sounds simple, and conceptually it is. The tricky bit lies in the practicalities of making useful maps of this variation, and then devising ways of treating the different bits differently.
PV is well established in the vineyards of California and Australia. In California, the emphasis has largely been on what is termed "remote sensing" – data collection through gathering aerial images, either by means of satellites or, more commonly, flying an aeroplane or a drone over the vineyards. The pictures are "multispectral": they consist of overlapping images taken at different wavelengths of light, each giving different sorts of information. In Australia, where many vineyards are picked by machine harvesters, PV data collection is typically done through the use of yield monitors. These devices are attached to harvesters and, when used with GPS, enable yield maps to be generated. Typically, the areas with the heaviest yields are of lower quality than those with the lower yields. Supply a vine with deep soils, plenty of nutrients and adequate water, and it will respond by growing a rich, deep green canopy, with tall shoots and lots of leaves.
This is known as high vigour and, while it might look very healthy, it's not great for wine quality. The vine will produce a generous yield of grapes, but these won't ripen as well as those on a less vigorous vine. When conditions limit canopy growth, the vine puts more effort into ripening fruit, and so the perfect vineyard is one where the vines are just stressed a little, such that about three-quarters through the growing season the canopies stop growing and the focus of the vines is on ripening grapes.
Neither of these technologies, however, is particularly useful in the UK. Aerial imagery works best when the space between the rows of grapes is bare earth (in the UK it's usually has grass or a cover crop), and yield monitoring requires mechanical harvesters (Denbies Wine Estate in Surrey has the only one in the UK).
But at Chapel Down, PV has been used successfully on new planting sites. "It has primarily been used in vineyard establishment where we have wanted to determine the variation of soil nutrient availability and pH levels [how acid or alkaline the soil is], so we can address any variations across the site before we plant," Lewis says. "It is important to create as even a planting area as you can."
Lewis analyses soil pH, phosphorus and potassium levels across the site. If there are any uneven areas, he can either even out this variation by adding nutrients or other soil treatments or take into account the variability by planting different grape varieties or using different types of rootstock in the different zones. Almost all vines are grafted on to special rootstock that is resistant to a ubiquitous phylloxera aphid which almost wiped viticulture out in the late 19th century.
Rootstock varieties have different properties, and this can be an effective management tool. For example, in deep, fertile soils vines tend to be too vigorous. "In the vineyard we have just planted in Faversham we have a row 100m long, and we have split the rootstock half way down because our soil analysis determined that the soil changed significantly," reports Lewis. "We have kept the same variety, but we changed the rootstock. We can do a lot before we put the vine in the ground to stack the cards in our favour."
Why is variation in the vineyard such a bad thing? It's largely to do with the ripening of grapes. If you have a mixture of under-ripe, ripe, and over-ripe grapes in the same vat, the resulting wine will not be more complex, it will just taste less nice and will be of lower quality. As grapes ripen, they lose the green, astringent flavours and tart acidity that characterises the unripe state, and they begin to taste sweeter and more fruity. As they become over-ripe, they accumulate extra sugar, their fruit flavours turn jammy and the acidity disappears. In cool climates such as the UK under-ripeness is the big risk, whereas in warmer climates, over-ripeness can mean the wines end up with sky-high alcohol levels and are less stable because of lower acidity. Variation in the vineyard can result in a mixture of ripeness levels in the same batch of grapes, because it's rarely economic to harvest the same vineyard more than once. Besides, it is very hard to distinguish degrees of ripeness by eye, unless the grapes are excessively under-ripe, or are so ripe that they are raisined. So the dream of any vineyard manager is to be able to harvest grapes at the perfect time, where they will all show even levels of appropriate ripeness. This is what the world's great vineyards tend to do naturally. What PV promises is the potential to manage an otherwise average vineyard in such a way as to make it a high quality vineyard, and this is why there's so much interest in it.
Lewis has also used PV on established vineyards. "We have also used it post planting where we have done soils analysis across an entire site on a grid system," he explains. "Each grid point has been assessed separately. We have taken this information, put it into a GIS (geographical information system), which has been plugged into a variable rate spreader on the back of a tractor, and it has been able to deliver fertiliser at prescribed rates depending on the nutrient status of the soil."
The GIS is one of the keys to PV. The software takes the data measured in the field and then creates a map. The real strength of this approach is that you can take different levels of information and combine them. For example, you might collect data on canopy vigour, and also data on soil composition and structure. Both data sets can be combined to make a map of the vineyard that can then be used to direct management strategies. This map has what's known as temporal and spatial stability – it's true from year to year, because its basis is the physical properties of the site.
One of the leaders in the push for PV is Jim Newsome, who came to the wine industry after a career in IT. He owns a small vineyard in Dingleden, but last year decided to set up Veni Vidi Viti, a vineyard technology company specialising in PV solutions. Newsome spent the 2013 growing season proving that his technology worked, and this year is looking to build a roster of clients across the UK.
The focus of his work is measuring canopy vigour across the vineyard using two connected devices mounted on a quad bike which is driven up and down the vine rows. The first of these devices is a specialised camera, called a GreenSeeker. This shines a light on the canopy and measures the red and infrared reflectance, from a distance of 70–120cm. This gives an indication of the density and extent of the foliage on the vine, and can be used to produce a map of the growth vigour. The second device is a handheld GPS, which is linked to the GreenSeeker.
"With your smartphone GPS you have a resolution of plus or minus three metres, which is pretty good," Newsome says. "My setup will give me a resolution of plus or minus 50cm." His enhanced GPS costs around £2,000. It's possible to get GPS down to a resolution of 5cm, but at the cost of £9,000. This sort of vineyard survey will give you an accurate vigour map of the vineyard to see where intervention is needed to even things out.
"There are lots of management techniques you can modify based on these data," says Newsome. "Leaf stripping is a classic example. In areas where there is high vigour you might leaf strip 80% [of the fruiting zone, the areas where the grapes are found] to try to get the sunlight in.
"An Italian company have just produced a variable-rate leaf stripper that feeds off a vigour map of the sort we would produce. It runs up and down the rows taking off more or fewer leaves depending on the map."
A quicker way to note variation in the vineyard is with an aerial view. Precision agriculture company SOYL now offers drones – or unmanned aerial vehicles, to use the jargon – that fly over the vineyard, capturing multispectral images. These can then be used to create vigour maps in the same way that Newsome's quad-bike devices do. But both Newsome and Lewis reckon that this method is not as useful in the UK. "I think it needs to be side-mounted if you are looking at the fruiting zone," says Newsome. "If you have an aerial view you have the problem of distinguishing the canopy from the cover crop."
Lewis says these sorts of images need a lot more post-processing using sophisticated software to make them usable, but sees some use in taking a quick look from above, even if it's not with sophisticated multispectral cameras. "We commissioned some aerial pictures with a regular camera, around veraison [the point in the vine growth when red grapes change colour from green to red] which is where you see the most variation," he says. "It gave us a bit of an indication where there might be areas of high or low vigour, so I could drive out and have a poke around."
Other hi-tech tools available to PV practitioners include electromagnetic induction sensors, which carry out a survey of the subsoil composition and show where the soil changes. Then you can dig pits to have a look at what's going on below ground.
Newsome says these surveys can only be used pre-planting stage as the metal posts used to support the vine trellis create interference.
Dr David Green, an academic at the University of Aberdeen, is working with a number of UK vineyards looking at potential for PV. "In the UK most vineyards are quite small compared with the European and North American vineyards, particularly the commercial ones," he says. Green believes the expense and expertise needed to make use of some of the snazzy new PV techniques, such a remote sensing, are currently prohibitive for the UK's vineyards, but he is confident that there are benefits to be had from high-tech grape-growing. "There is huge potential offered by small Wi-Fi sensors and networks for field data collection, and the rapidly growing possibilities provided by drones, which can carry small photographic sensors, thermal infrared sensors, and hyper-spectral instruments. All of these can yield new spatial and temporal information about variability in the vineyard."
It's easy to get carried away with all this vineyard technology, but it's really only doing on a large scale what dedicated vignerons have been doing for centuries. "It's no different from the vineyard manager who walks through his vineyard having a look," says Lewis. "But as the scale gets bigger you run out of hours in the day to do this." And as the English wine industry goes through its adolescent growth spurt and emerges onto the international stage, it looks as if PV tools could yield some corking results.
