Hacker News Reader

Comment by cjensen | Hacker News Reader

Nice idea, but what about the Elephant in the Room? How do you eliminate the buildup of salt in the soil which can ruin the farmland?

View on HN

You grow these GMO tomatos which thrive in salty soil and actively remove the salt by concentrating it in the leaves http://www.newscientist.com/article/dn1092-genemodified-toma...

What happens to the leaves? Do they also get harvested?

In the end I think you will get a salt concentration somewhere. Your compost may not be so usable for example. You provably have to be careful where you put it if you are dealing with any significant volume.

The leaves of the tomato plant are poisonous, even before you think about the salt.

Maybe they should bring the crops to the sea rather than bring the sea to the crops.

I've been wondering abut the viability of farming in floating polytunnels. They could even be temporarily submersible to weather storms.

How would a polytunnel be submersible? A poly tunnel is a really flimsy structure. Just going down 10 meters double the pressure (1 bar), and being any shallower isn't going to protect you from the surface water churn. Not to talk about the effort to push thousands of cubic meters of air under water. Not very practical I don't think. :)

Polytunnels are flimsy in compression, but clear plastic can be very good in tension and can contain a bar or so of pressure fairly easily, so it may be feasible. It was only one of the solutions I thought of for coping with storms if you are growing out at sea. The other two are either being able to reel them back onto land, or just making them short and tough, so they can just roll over the waves. The buoyancy problem isn't that difficult though as you can have counter-buoyancy that rises when they sink.

Building a submarine out of a polytunnel just isn't going to work. There are so many better ways to spend money. There are literally many thousands of km of dessert coastline where we can build greenhouses and grow vegetables where nothing else can grow. See my other entries in this thread.

"So nine times out of ten the salt is retained in the leaves of the plant, so you’d have to eat many many kilos of potatoes before you’d exceed your recommended salt intake. But some of the salads are heavy with salt"

Then how are the leaves disposed of, I do not know. Fed to pigs or burnt perhaps, if they were simply used as mulch you would still wind up with a buildup of salt in the soil.

Burning leaves a pile of salt. I, too, am curious where they expect the salt to disappear to.

If you burn it, and have a pile of salt, it might be possible to remove the ash and keep the salt.

Burn the leaves and use the ash in artisanal soap?

Maybe they can just dump them back into the sea.

Salt is worth money. If you have a bunch of salty leaves, you should be able to process them and get the salt out.

Might cost you more money to get the salt out than you can sell the salt for, though.

Just dump the leaves in the ocean. Biodegradable and the salt came from the ocean anyways. The leaves if too concentrated will intake a lot of water and their cells burst. Or the leaves won't be too concentrated and will be eaten by nature.

My takeaway from the article was that this was targeted at places where sea water contamination of farmland was a regular event, or where like in the northern areas of the Netherlands, keeping seawater off farmland is unsustainably expensive.

A lot of Dutch farming in greenhouses is already hydroponic, i.e. Little or no soil is involved.

Would hydroponics be efficient on a large scale like this?

My limited experience of hydroponics tells me that it is economical for high value crops like vegetables, selling to a European or Californian market. Thera are hydroponic greenhouses which are 100+ hectare (250 acres), but for staple crops like potatoes I think it is going to be prohibitively expensive to try to grow in greenhouses with hydroponics.

If you are going to do hydroponics for veg and work with seawater then you can just as we'll go with the Seawater Greenhouse. http://www.seawatergreenhouse.com

Why would potatoes be anymore expensive than other staple crops?

Possibly but that defeats the advantage of using salt water. Efficient operations need only a small fraction of the water used in traditional agriculture.

Reply on news.ycombinator.com