If you’ve ever stood in the produce aisle and wondered why the smooth golden kiwifruit costs more than the fuzzy green ones sitting a foot away, part of the answer is that the golden one is a lot easier to kill. Not by you. By a bacterium that European growers have spent the better part of two decades fighting, and that has a particular appetite for the yellow-fleshed varieties.<\/p>\n
A fruit grower in the French Alps has now put a roof over his.<\/p>\n
The greenhouse opened on September 4 at Upaix, a village of 494 people in the Hautes-Alpes, roughly 2,400 feet up. It covers 3.7 acres of yellow kiwifruit vines, and the roof over them is 4,725 solar panels wired into a 1.53-megawatt array. REDEN, the French solar developer that built it alongside a local grower named Poincelet, paid for the whole structure<\/a>.<\/p>\n Because of something called Psa, or bacterial canker of kiwifruit. EPPO<\/a>, the organization that maintains the official European datasheet on the pathogen, describes it as the most important limiting factor in growing kiwifruit at all. The bacterium spends winter inside cankers on the trunk and canes, oozes out in late winter as a milky exudate, and then needs a ride to the next vine.<\/p>\n Rain gives it one. Wind-driven rain splash, showers, irrigation water and dirty pruning tools are how it travels inside an orchard, and high humidity is what it likes while it’s traveling. It also needs a way in once it lands, and the openings it uses are stomata, lenticels and fresh wounds, which in practice means hail cuts and pruning cuts. Frost injuries open more doors for it. Upaix is high enough that frost is a normal part of the calendar there.<\/p>\n Here’s where the color comes in. Yellow-fleshed kiwifruit is Actinidia chinensis<\/em>; the fuzzy green supermarket one is Actinidia deliciosa<\/em>. EPPO isn’t subtle about the difference, and calls the yellow one far more susceptible than the green. Some yellow cultivars are susceptible enough that an infected vine can die within one or two seasons. When the pandemic strain got loose in Italy, crop losses passed 60 million euros in a single year.<\/p>\n So a roof over yellow kiwifruit buys three things at once. It keeps rain off the canopy, it keeps hail off the canes, and it takes the edge off frost. That’s a fairly rational thing to spend money on if you’re planting the most vulnerable kiwifruit there is at altitude in the Alps.<\/p>\n It isn’t a magic wand, though, and I’d be doing you a disservice if I sold it as one. EPPO’s own control advice tells growers to bring the relative humidity down inside their orchards, and it specifically calls out orchards under hail nets, because a cover traps moisture and this bacterium is happiest in moisture. The fix is pruning green vines, by hand, on top of everything else. So a cover takes one job away from a grower and hands him a different one. REDEN hasn’t published a single agronomic number from the site yet, which is fair enough when the vines have only just gone under cover.<\/p>\n If you’re wondering whether any of this matters to you as an American: kiwifruit here is basically a California crop, and the federal government has gone to some trouble to keep Psa away from it. APHIS<\/a> blocked imports of kiwifruit plants and pollen from every country on earth to keep it that way, on the grounds that the pathogen wasn’t known to occur in the United States and that inspectors can’t reliably spot it on a symptomless plant at the border. Fruit and seed were never the problem, so your grocery run is fine.<\/p>\n REDEN did, all of it. The company sells these greenhouses as a turnkey farm building that the developer pays for, and it has been putting them up in France since 2010. That arrangement is the reason a 3.7-acre greenhouse exists on a fruit farm in a village of 494 people at all.<\/p>\n The output figure is where I’d push back a bit. REDEN says the array makes the yearly electricity consumption of about 1,050 people, close to twice the population of the commune. The population half checks out, since INSEE counts 494 residents at Upaix. But people are a strange unit for electricity, and I’d rather have megawatt-hours. REDEN publishes megawatt-hours elsewhere: about 5,600 a year from a 4.6-megawatt greenhouse in Maine-et-Loire, about 4,000 from a 3-megawatt one in Ari\u00e8ge. I ran those ratios against 1.53 megawatts and got somewhere in the neighborhood of 1,900 to 2,000 megawatt-hours a year for Upaix. That’s my arithmetic, not the company’s, so treat it as a ballpark.<\/p>\n I also divided the array rating by the panel count, and each module works out at about 324 watts. That’s ordinary hardware. You’d find the same panel on a warehouse roof, and the difference at Upaix is what’s growing underneath it.<\/p>\n Nobody can tell you that about this site yet, and the wider evidence cuts both ways. Panels over a crop take light away from the crop, and a kiwi vine wants light like everything else growing outdoors. An Italian team at Bari has already drawn a line on how much you can take: hold shading under 30 percent<\/a> or fruit yield and quality start sliding, whatever the shade is doing to soil temperature underneath.<\/p>\n A German apple grower has had the opposite experience, with fruit ripening 10 to 12 days later<\/a> than the orchard next door under 1,148 panels hung 16 feet up, and sunburn damage he says disappears completely depending on how the array is built. Kiwifruit isn’t an apple and a sealed greenhouse isn’t an open canopy, so I wouldn’t carry that result across as if it transfers. It does show the shade can pay.<\/p>\n What’s missing at Upaix is the same thing that’s missing under most new agrivoltaic hardware in Europe, which is a weighed harvest. Roofs are easy to photograph on opening day, and crates of fruit take a lot longer. RWE’s arrays over alfalfa and rosemary in southern Italy are in exactly the same position<\/a>, with the panels up and nothing yet weighed underneath.<\/p>\n One agronomic benefit does get claimed already. The moving shade cast by the panels cuts evapotranspiration, REDEN says, so the vines should need less irrigation water than they would under a conventional greenhouse. That’s a REDEN statement rather than a measurement anybody has published, and in a district where the prefecture only lifted this summer’s water restrictions on September 2, it’s the number I’d most want to see.<\/p>\n Vincent Larribe, who runs REDEN’s development work in France, told Tecsol Quotidien<\/a> the project shows what agrivoltaics can do when it’s designed around the farming instead of the other way around. He may well turn out to be right. The vines are in and the array is up as of the September 4 opening, and Le Dauphin\u00e9 Lib\u00e9r\u00e9<\/em>, which covered it, reports the first pick is expected about a year from now.<\/p>\n","protected":false},"excerpt":{"rendered":" If you’ve ever stood in the produce aisle and wondered why the smooth golden kiwifruit costs more than the fuzzy … <\/p>\nSo why does a kiwi vine need a roof?<\/h2>\n
Somebody has to pay for a greenhouse<\/h2>\n
So does the shade actually help the fruit?<\/h2>\n