In Paris, urban farmers are trying a soil-free approach to agriculture that uses less space and fewer resources. Could it help cities face the threats to our food supplies?

在巴黎，城市农民正在尝试一种使用更少空间和资源的无土农业方法。它能帮助城市应对粮食供应面临的威胁吗？

On top of a striking new exhibition hall in southern Paris, the world's largest urban rooftop farm has started to bear fruit. Strawberries that are small, intensely flavoured and resplendently red sprout abundantly from large plastic tubes. Peer inside and you see the tubes are completely hollow, the roots of dozens of strawberry plants dangling down inside them. From identical vertical tubes nearby burst row upon row of lettuces; near those are aromatic herbs, such as basil, sage and peppermint. Opposite, in narrow, horizontal trays packed not with soil but with coconut fibre, grow cherry tomatoes, shiny aubergines and brightly coloured chards.

在巴黎南部一座引人注目的新展览馆顶部，世界上最大的城市屋顶农场已经开始开花结果。小巧玲珑、味道浓郁、鲜红欲滴的草莓从大型塑料管中大量萌发。往里一看，管子完全是空心的，几十株草莓的根系垂在里面。旁边同样的垂直管子里，一排排莴苣破土而出；附近还有罗勒、鼠尾草和薄荷等芳香草本植物。对面狭窄的水平托盘里装的不是泥土，而是椰子纤维，里面种着樱桃番茄、闪亮的茄子和色彩鲜艳的甜菜。

Pascal Hardy, an engineer and sustainable development consultant, began experimenting with vertical farming and aeroponic growing towers – as the soil-free plastic tubes are known – on his Paris apartment block roof five years ago. The urban rooftop space above the exhibition hall is somewhat bigger: 14,000 square metres and almost exactly the size of a couple of football pitches. Already, the team of young urban farmers who tend it have picked, in one day, 3,000 lettuces and 150 punnets of strawberries. When the remaining two thirds of the vast open area are in production, 20 staff will harvest up to 1,000 kg of perhaps 35 different varieties of fruit and vegetables, every day. 'We're not ever, obviously, going to feed the whole city this way,' cautions Hardy. 'In the urban environment you're working with very significant practical constraints, clearly, on what you can do and where. But if enough unused space can be developed like this, there's no reason why you shouldn't eventually target maybe between 5% and 10% of consumption.'

帕斯卡尔-哈迪（Pascal Hardy）是一名工程师和可持续发展顾问，五年前他开始在自己的巴黎公寓楼屋顶上试验垂直耕作和气培种植塔（无土塑料管）。展览馆上方的城市屋顶空间更大一些：14,000 平方米，几乎相当于几个足球场大小。由城市青年农民组成的团队已经在一天之内采摘了 3000 株生菜和 150 蒲式耳草莓。当大片空地的其余三分之二投入生产后，20 名员工每天将收获多达 1000 公斤、约 35 个不同品种的水果和蔬菜。哈迪警告说："显然，我们不可能用这种方式养活整个城市。在城市环境中，你所能做的、能在哪里做，显然都受到很大的实际限制。但如果能像这样开发足够多的闲置空间，就没有理由不最终将目标锁定在 5%-10%的消耗量上。

Perhaps most significantly, however, this is a real-life showcase for the work of Hardy's flourishing urban agriculture consultancy, Agripolis, which is currently fielding enquiries from around the world to design, build and equip a new breed of soil-free inner-city farm. 'The method's advantages are many,' he says. 'First, I don't much like the fact that most of the fruit and vegetables we eat have been treated with something like 17 different pesticides, or that the intensive farming techniques that produced them are such huge generators of greenhouse gases. I don't much like the fact, either, that they've travelled an average of 2,000 refrigerated kilometres to my plate, that their quality is so poor, because the varieties are selected for their capacity to withstand such substantial journeys, or that 80% of the price I pay goes to wholesalers and transport companies, not the producers.'

不过，最重要的是，这可能是哈迪的城市农业咨询公司 Agripolis 工作的真实展示，该公司目前正在接受来自世界各地的咨询，要求设计、建造和装备新型的无土市内农场。这种方法有很多优点，"他说。首先，我不太喜欢我们吃的大多数水果和蔬菜都经过大约 17 种不同杀虫剂的处理，也不太喜欢生产这些水果和蔬菜的集约化耕作技术会产生大量温室气体。我也不喜欢这些水果和蔬菜平均要经过 2000 公里的冷藏运输才能送到我的餐桌上，我也不喜欢它们的质量如此之差，因为这些品种是为了能够承受如此长途的运输而被挑选出来的，我也不喜欢我所支付的价格中有 80% 是批发商和运输公司的，而不是生产商的。

Produce grown using this soil-free method, on the other hand – which relies solely on a small quantity of water, enriched with organic nutrients, pumped around a closed circuit of pipes, towers and trays – is 'produced up here, and sold locally, just down there. It barely travels at all,' Hardy says. 'You can select crop varieties for their flavour, not their resistance to the transport and storage chain, and you can pick them when they're really at their best, and not before.' No soil is exhausted, and the water that gently showers the plants' roots every 12 minutes is recycled, so the method uses 90% less water than a classic intensive farm for the same yield.

另一方面，使用这种无土栽培法种植的农产品--仅靠少量富含有机养分的水在管道、塔架和托盘组成的闭合回路中循环--"在这里生产，在当地销售，就在下面。哈迪说："这些水几乎不经过任何运输。你可以根据作物的风味，而不是它们对运输和储存链的耐受性来选择作物品种，你可以在它们真正达到最佳状态时采摘，而不是在采摘之前。这种方法不会耗尽土壤，而且每 12 分钟轻轻喷洒在植物根部的水都会被循环利用，因此在产量相同的情况下，这种方法比传统的集约型农场少用 90% 的水。

Urban farming is not, of course, a new phenomenon. Inner-city agriculture is booming from Shanghai to Detroit and Tokyo to Bangkok.

当然，城市农业并非新现象。从上海到底特律，从东京到曼谷，城市内的农业都在蓬勃发展。

Strawberries are being grown in disused shipping containers, mushrooms in underground carparks. Aeroponic farming, he says, is 'virtuous'. The equipment weighs little, can be installed on almost any flat surface and is cheap to buy: roughly €100 to €150 per square metre. It is cheap to run, too, consuming a tiny fraction of the electricity used by some techniques.

人们在废弃的集装箱里种植草莓，在地下停车场种植蘑菇。他说，气生栽培是 “良性 ”的。设备重量小，几乎可以安装在任何平面上，而且购买成本低：每平方米大约 100 至 150 欧元。它的运行成本也很低，耗电量仅为某些技术的一小部分。

Produce grown this way typically sells at prices that, while generally higher than those of classic intensive agriculture, are lower than soil-based organic growers. There are limits to what farmers can grow this way, of course, and much of the produce is suited to the summer months. 'Root vegetables we cannot do, at least not yet,' he says. 'Radishes are OK, but carrots, potatoes, that kind of thing – the roots are simply too long. Fruit trees are obviously not an option. And beans tend to take up a lot of space for not much return.' Nevertheless, urban farming of the kind being practised in Paris is one part of a bigger and fast-changing picture that is bringing food production closer to our lives.

以这种方式种植的农产品的售价通常高于传统的集约型农业，但低于以土壤为基础的有机种植者。当然，农民用这种方式种植的作物也有局限性，大部分农产品都适合在夏季种植。他说："我们不能种植根茎类蔬菜，至少现在还不行。萝卜还可以，但胡萝卜、土豆之类的根太长了。果树显然也不行。而豆类往往占用大量空间，收益却不高。尽管如此，在巴黎开展的这种城市耕作只是快速变化的大环境中的一部分，它让粮食生产更加贴近我们的生活。