Growing crops on Martian soil

[More Boosters]

Yes, I recently watched The Martian. But I've had a long standing interest in the issue and the extent of my knowledge was that the soil has perchlorate salts that are apparently poisonous to humans and plants. How true is this? What other challenges are there to overcome like heating, water, no microbial life in soil etc.

[Kerbart]

I'm not a biologist but an easy way to get around the soil problems would be to use hydroculture.

[Nibb31]

Yes, the author of The Martian was aware of the perchlorate problem, but he waved it away because he wanted to write a good story. In reality, removing perchlorates from Martian soil isn't something that we know how to do yet, although scientists are working on it.

[lajoswinkler]

Yes, the author of The Martian was aware of the perchlorate problem, but he waved it away because he wanted to write a good story. In reality, removing perchlorates from Martian soil isn't something that we know how to do yet, although scientists are working on it.

We know how to do it. All perchlorates are highly soluble in water. All you need to do is to grind and wash the regolith (it's not soil, it lacks the organic part) which will remove some other components, too, but hey, at least you don't have perchlorates inside anymore.

[Requia]

I'm not a biologist but an easy way to get around the soil problems would be to use hydroculture.

I know just enough to know that you need a nutrient bath that's fairly hard to make, and you can't grow potatoes that way. Pretty much every successful soil free setup just grows veggies, which don't have the calorie density.

[marach]

Yeah the perchlorates just wash away an additional step to the martian would have been pouring water through the regolith for a few weeks distilling the pour off and chucking the salts very carefully out the airlock. Though in truth the water treatment plant would likely be designed to remove them from water anyway since some would come in as dust every time the airlock was used...

[WinkAllKerb'']

send tons of various seeds there, try, else you never know ... do it, don't discuss about it ... n o n e e d a t a l l t o w a s t e t i m e a b o u t t h a t

. question ? no that's fine then ...

Edited November 6, 2015 by WinkAllKerb''

[marach]

if the salts are soluble in water, and just need to be washed out, then wouldn't they be washed out when he waters the plants? This doesn't seem terribly complicated to me...

I know the floor of the habitat is going to stop them from completely disappearing, but I'd imagine that the majority would be washed away from the roots.

The problem is the perchlorates would be suspended in the water next to the roots, you need to remove them from the area completely hence filtering water through the soil a few dozen (a few thousand would be better) times to remove them.

[WinkAllKerb'']

ask the netherlands or any other "growshop" specialist .. this start gettin' borin' ... kinda like trichrome mushroom and vegetal carbonic evaporation law ... oil any talk about oil ?

[WinkAllKerb'']

Have you done much farming?

we should ask harvy' xDr

[fredinno]

We know how to do it. All perchlorates are highly soluble in water. All you need to do is to grind and wash the regolith (it's not soil, it lacks the organic part) which will remove some other components, too, but hey, at least you don't have perchlorates inside anymore.

"Other components" could be minerals essential for plant growth.

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Have you done much farming?

Seriously though, most of the water that we use on crops (or from rain) goes right down through the soil, and into the water table - in this case, making a puddle on the plastic underneath. The salt would probably be left down at the bottom of the soil column, as the water evaporated, so I'd imagine that there's a layer of those salts at the very bottom of his soil. Is that an issue though? I really don't know...

Well, that could lead to salinification of the soil on the long term, which would render the land bad for farming. It also happens to be the chief cause of desertification .

[WinkAllKerb'']

welcome to the terraforming era ... don't tell devo plox ... xDr there no way to land and land to a new way ... seriously this gettin old ... with available teks'

(remember to check for local evoluted or not species before terraforming the whole planet btw could be nice)

Edited November 6, 2015 by WinkAllKerb''

[marach]

Have you done much farming?

Seriously though, most of the water that we use on crops (or from rain) goes right down through the soil, and into the water table - in this case, making a puddle on the plastic underneath. The salt would probably be left down at the bottom of the soil column, as the water evaporated, so I'd imagine that there's a layer of those salts at the very bottom of his soil. Is that an issue though? I really don't know...

It's 10cm of soil the roots are gonna hit bottom also the soil is damp not saturated so no most would be in Suspension.

[Albert VDS]

There are bacteria that eat perchlorates, they also create waste heat as a bonus.

An other way might be to burn the perchlorates.

[Finox]

Has anyone thought that these perchlorates might be useful in agriculture? Naturally occurring deposits of nitrates often have perchlorates in them here on Earth, the same could be true of Mars. Furthermore ammonium perchlorate decomposes fairly easily when heated into Oxygen, Nitrogen, Chlorine and Water, each of which would be useful for farming on Mars, aside from the Chlorine anyway.

[Northstar1989]

"Other components" could be minerals essential for plant growth.

You would have to add minerals anyways. Even many soils here on Earth are deficient in one nutrient or another. That's why we fertilize.

Well, that could lead to salinification of the soil on the long term, which would render the land bad for farming. It also happens to be the chief cause of desertification .

The accumulation of salts in the topsoil (salination) that you're referring to is due to irrigation schemes in which the soil is waterlogged, then allowed to dry out, or insufficiently wetted in the first place.

One of two things happens: either salts from the irrigation water itself accumulate due to inadequate hydration to leach it down to lower layers; or the inadequate hydration of the soil allows capillary action pulling salts up from lower layers to dominate the balance. Either way, with sufficient drainage and hydration (enough to provide an adequate "leaching fraction") salt is washed down into the water table, not drawn up from it... The areas where soil becomes excessively salty for farming usually are not using proper technique in the irrigation of the soil- as they don't have enough water to work with in the first place. *This* is what leads to salination...

Wikipedia summarizes it well:

"The primary method of controlling soil salinity is to permit 10-20% of the irrigation water to leach the soil, be drained and discharged through an appropriate drainage system. The salt concentration of the drainage water is normally 5 to 10 times higher than that of the irrigation water, thus salt export matches salt import and it will not accumulate."

https://en.wikipedia.org/wiki/Soil_salinity#Salinity_due_to_irrigation

https://en.wikipedia.org/wiki/Soil_salinity_control

As a side-note, if you allow too much water to leach, then you end up with the water table rising and the soil becoming waterlogged. Which is also not good for agricultural yields as some crops are not tolerant of being continuously waterlogged... You need to stick to that 10-20% range.

To get to the point here, though- there would be a risk of the perchlorates being drawn back up into the upper layers of soil via capillary action if they were simply allowed to accumulate on the bottom. It would be highly advisable to wash all the perchlorates out of the soil first, and only *then* attempt agriculture, supplementing/replacing and minerals and macronutrients (such as soil nitrates) as necessary...

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Has anyone thought that these perchlorates might be useful in agriculture? Naturally occurring deposits of nitrates often have perchlorates in them here on Earth, the same could be true of Mars. Furthermore ammonium perchlorate decomposes fairly easily when heated into Oxygen, Nitrogen, Chlorine and Water, each of which would be useful for farming on Mars, aside from the Chlorine anyway.

There's no reason to think you couldn't break down the perchlorates into useful elements/nutrients (other than the time/energy required). Many poisonous compounds can be useful when broken down, Even Cyanide is simply made of Nitrogen and Carbon, after all. But you probably would only have use for the products of breaking down a minor fraction the perchlorates- the rest you would simply want to throw out...

Regards,

Northstar

Edited November 7, 2015 by Northstar1989

[lajoswinkler]

if the salts are soluble in water, and just need to be washed out, then wouldn't they be washed out when he waters the plants? This doesn't seem terribly complicated to me...

I know the floor of the habitat is going to stop them from completely disappearing, but I'd imagine that the majority would be washed away from the roots.

It takes some time because some of it is physically locked inside grains. It really needs to be properly reprocessed. Milling, washing, drying, compacting the regolith, and water reclamation.

"Other components" could be minerals essential for plant growth.

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Well, that could lead to salinification of the soil on the long term, which would render the land bad for farming. It also happens to be the chief cause of desertification .

They can be returned as most if not all of them crystalize before the perchlorates do as their solubility is lower. Proper reprocessing is needed. Complex and expensive.

There are bacteria that eat perchlorates, they also create waste heat as a bonus.

An other way might be to burn the perchlorates.

Only if they promptly reduce them to chlorides. Chlorates, chlorites, and hypochlorites are much more reactive and would downright oxidize the plant.

I guess GM bacteria would be of immense help here.

ask the netherlands or any other "growshop" specialist .. this start gettin' borin' ... kinda like trichrome mushroom and vegetal carbonic evaporation law ... oil any talk about oil ?

Well, that explains a lot.

[fredinno]

The soil is already 'salinified', correct? The water should wash the salt out, unless I'm misunderstanding something...

"Re-salinification" in a sense- the water, evaporates, leaving behind the salt in it. Over time it accumulates, causing salinification.