There is, to the south of a prominent empire, a load of deserts with rocky, sandy soil. It's by the ocean and desalination comes easy to said empire due to several magical appliances they have. You need not concern yourself over how said appliances work, just take it for granted that water will not be a problem. Neither will energy.

The main goal is to convert these desert regions into farmland where cereal crops can be grown on a large scale, to turn barren land into breadbaskets for the future colonization of the region. The many native tribes just sold their land for what they considered very profitable terms, so the politics of land are also not a concern.

My question is regarding just how sand can be turned into fertile soil. Naturally, just throwing lots of water at it won't work. So what do you need to do to the sand, or what do you need to add, to make it into a good environment for large scale commercial agriculture?

PS: no need to worry about topography either. It can be changed.

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    $\begingroup$ Have you looked at real world attempts to do this? In many cases it is a simple as adding water. $\endgroup$
    – John
    Commented Jun 25 at 10:56
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    $\begingroup$ Sandy is one (easy) thing, rocky is another (more difficult) thing. Irrigation does wonders on sandy soil. Please note that you said "sandy $\rightarrow$soil$\leftarrow$", not an endless sea of sand. $\endgroup$
    – AlexP
    Commented Jun 25 at 12:24
  • $\begingroup$ The Soviet Union had this very idea in mind when "the Amu Darya river in the south and the Syr Darya river in the east were diverted from feeding the Aral Sea to irrigate the desert in an attempt to grow cotton, melons, rice and cereals." The result was the near destruction of the previously vital and beautiful Aral Sea. The question isn't "can we do it?" We've already done it. The question is, "what are the consequences?" Note that @AlexP is correct. I'm treating "desert" as "dry land." The nature of that land is important. $\endgroup$
    – JBH
    Commented Jun 25 at 22:05
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    $\begingroup$ @JBH: It is maybe useful to point out that the attempt to grow cotton, melons, rice and cereals was completely successful. Of note, we don't hear from Kazakhstan, Turkmenistan or Uzbekistan of any proposal to return things to the state they were before the irrigation projects. $\endgroup$
    – AlexP
    Commented Jun 25 at 22:20
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    $\begingroup$ @JBH yesterday I had a training at work about human effect on environment. And the whole third module of that training was about the Aral sea ;) $\endgroup$
    – frarugi87
    Commented Jun 26 at 10:15

9 Answers 9


As no additional information is given regarding the degree of technology of your empire, I would give a "timeless" method of working with nature rather than against it. Desert has occasional rains, and some form of vegetation is present. Digging trenches to create an "uneven" terrain is one good method of making rain water drain and seep into the lower areas of the terrain. This area will support a much greater biomass of plants. Plants like grass are especially good at holding the soil with their roots. The falling leaves will also lodge between the newly growing leaf blades. Eventually, a topsoil will form. This project was done successfully in Spain.

How Spain is Turning its Deserts into a Farmland Oasis - GREENING THE DESERT PROJECT

I've seen other videos of similar projects in Africa as well. Sometimes there is more rain than what the trenches could handle. Often local rocks are gathered to build trench walls which retain the soil in place and avoid their collapse before the plants get established. In the African project, for instance, it was found out that planting the tree as a seed in the trench yielded more robust plants which did not require much (if any) human intervention in watering. Though seed mortality is higher than that of mature ones, overseeding (with moderation) is often a faster, cheaper and more practical approach.

More technologically advanced societies can incorporate drip irrigation, germination trays and organic farming like this project in Mexico:

How He Turned Desert Sand Into Fertile Farm Land In 3 Months!

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    $\begingroup$ I was working on an answer that was basically saying exactly this. Plants do grow in the dessert. You need sun, water, and decaying biomass. $\endgroup$ Commented Jun 25 at 21:02
  • $\begingroup$ I have seen documentaries that have shown places in India and China that do this with success. $\endgroup$
    – Fred
    Commented Jun 26 at 13:54
  • $\begingroup$ Adding a lot of water to a large stretch of desert will also bring down the temperatures there, the energy going into evaporation of water. This can make the temperature more livable for some plants. Ever looked at pictures of a desert after those rare rains? Lots of plants spontaneously start growing, as their seeds survived mixed into the soil. As long as you keep adding some water, and scatter the seeds of some soil enriching plants that can survive the temperatures/sunlight exposure, the process of getting the farmland would be mostly automatic. $\endgroup$
    – vinzzz001
    Commented Jun 27 at 9:06

Depends on the kind of desert

Some deserts already have useable soil, they are just really dry places that need irrigation as the accepted answer has pointed out. However, other deserts are not just dry, but thier soil is completely ruined; so, these guys need a lot more work.

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If you're dealing with a desert where the landscape looks cracked, that means that the soil already has clay in it, and probably already has enough bioavailable resources to get started. However, if you are talking about a sand desert more like the Sahara, then just adding water is not enough. You'll need to do some soil restoration first before the land becomes agriculturally sustainable.

There are places in North Africa where sandy deserts are used for agriculture, but because the soil was not repaired first, they require about 4 times as much water and fertilizer to maintain as other farmlands, and unless the farmers are very careful with thier fertilizer blend, it's easy to make the soil toxic over time with neutrants that retain in sand better than others.

So if you are dealing with a sandy desert, you will need to do the following:

Step 1: Improve water/nutrient retention

The hardest part about farming a sandy desert is not the heat, the dryness, or even the salt. It's the inability for the sand to retain water and nutrients. When you place fertilizer in pure sand, and then add water, the water causes most of the components of the fertilizer to wash away leaving you with inert sand which most plants can not get enough micronutrients out of to survive.

The best way to solve this is to import clay which you can mix into the sand to create lome. When water mixes with clay it makes the clay sticky and bind to the sand allowing water and nutrients to be retained better.

Since this is a desert, you will probably also want to add charcoal to the soil. It will further increase the soil's water retention and add small amounts of certain biologically available nutrients to the soil to help get things kick started.

Cereal grasses especially tend to prefer loamy or clay based soils because they are especially good at breaking up harder soil which helps them outcompete many kinds of weeds; however, if you do not have the resources to import tons of clay and charcoal, it's better to pick a crop that prefers more sandy conditions anyway. I'd suggest tomatoes, peppers, garlic, onion, or cucumbers for a hotter desert, or carrots and potatoes for a colder desert.

Step 2: Fix soil acidity

Most deserts tend to be far too alkaline for most crops, and most agricultural plants make the soil even more alkaline. Many deserts today exist because of bad farming practices depleting soil acidity; so, you need to plant starter crops that will help with this. Starting off with trees is generally a good first step because they will make the soil more acidic, uptake the extra salt, and their large root structures and high foliage are especially good are preventing erosion as the soil builds. Evergreens are a popular choice because they grow quickly and can be harvested in as little as 10 years for thier lumber.

If you don't want to wait, you could instead try adding sulfur to soil. This is only a so-so solution because it still does not address the extra salt or other scarce micro neutrants, but it does get the job done. It will acidify the soil making it good enough to start growing stuff, though your soil will be far less stable than if you have those wide deep tree roots left in the ground holding everything together

Again, it's typically better to plant what grows well in your given soil than just planting what you want. A better solution for overly acidic and salty soil could be olive trees. They take a while to mature compared to other crops, but they are very long lived, and thier oil is a particularly profitable cash crop. They are also a good companion crop because they are so good for soil conditions; so, you might want to plant rows of olive trees with the plan to grow other stuff in between.

Step 3: Keeping the soil productive

One of the big problems with agricultural desertification is a poor choice in cover crops. It's common knowledge that wheat takes up nitrogen and legumes put it back, and some other thing can be planted in winter to prevent erosion, but soil is more complex than this. If you are already coming from the brink of failed soil, you want to make sure your crop choices leave your land better each year you plant. Not worse.

For this you will need a mix of cover plants that can scavenge micronutrients from that sand, build biomass, aerate the soil, encourage microbial growth, attract pollinators, etc. One mix that's been gaining popularity lately is the 5-Cousins method: Amaranth, Cowpeas, Buckwheat, Daikon Radish, and Sorghum. Sown together, these guys will build up your desert soil year after year into progressively better soil needing little to no outside fertilizers and a minimum of water.

  • $\begingroup$ And those cover crops add a lot of biomass to the subsurface soil which also increases the soil acidity. $\endgroup$
    – David R
    Commented Jun 26 at 14:58
  • $\begingroup$ The key to greening the desert is to stop the soil erosion by wind, which can be done only by planting... Indeed this is what's being done in a large swaths of Subsaharan Africa, but there they include trees to reduce wind erosion. This is a fact known wide and far - majority of Europe's farmland was for centuries divided by rows of trees, that would protect soil and crops from winds. Same was done with roads, especially in regions where snow was normal occurence - roads with tree canopy saw much reduced snowfall, making it easier to find and then negotiate. IOW: plant, plant, plant... $\endgroup$
    – AcePL
    Commented Jun 26 at 15:11
  • $\begingroup$ @AcePL, Mostly... but what you plant matters too. Because the OP wants to do cereal crops, it complicates things a lot because excessive cereal crop growth is actually a big contributor to desertification. If he just wanted to grow whatever will grow, then this answer would be a lot more simple. $\endgroup$
    – Nosajimiki
    Commented Jun 26 at 16:09
  • $\begingroup$ But you will not be able to grow anything edible in the sand. First, the topsoil needs to be, basically, created. Only after several dozens of cycles the humus will be strong enough to support planting something edible. It will not support grain crops for a really long time without protection such as trees, significant source of water and so on. Desert is barren because it's barren, and not because it's desert. For example, Sahara was lush green not so long ago (geologically speaking), but once huge floods came and took the topsoil with it, it left only rock and sand, unable to support plants. $\endgroup$
    – AcePL
    Commented Jun 27 at 6:36

Israel, Egypt, Saudi Arabia, Lybia and many other desertic countries have done what you are asking just by having access to water, either from underground, rivers or desalinated from the sea.

It happens also in any desert oasis: just having water makes miracles in developing a soil where vegetation can grow.

  • $\begingroup$ But is it really possible? As far as I know, sandy soil has no nutrients and won't hold water well. $\endgroup$
    – Thales
    Commented Jun 25 at 12:29
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    $\begingroup$ @Thales: Sandy soil is soil with more or less sand in it. It is far from being the worst kind of soil for agriculture. If the question intends to refer to actual pure sand it must say so; sand is not soil. $\endgroup$
    – AlexP
    Commented Jun 25 at 13:29
  • $\begingroup$ Soil salinity can be an additional problem intruduced by irrigation due to excessive evaporation. But that can be basically solved with even more water. $\endgroup$
    – LazyLizard
    Commented Jun 25 at 14:03
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    $\begingroup$ @Thales Re-read what was stated in the answer. It’s been done in real life, repeatedly. As long as there’s actual soil and not just sand and rock, it’s doable. You may need more careful selection of crops, and you will probably need to fertilize more than would be needed in less arid climates, but that doesn’t mean it’s not doable. $\endgroup$ Commented Jun 25 at 17:32
  • $\begingroup$ It is doable even with pure sand, it just takes longer. But still not a lifetime project. $\endgroup$
    – fraxinus
    Commented Jun 25 at 20:23

I would leave the soil as is. Changing it requires lots of efforts and time and there is very little interesting about it. It would turn you story into a book on agriculture.

"Just throwing lots of water at it won't work" - not necessarily.

The main mechanism of energy storage in grain is carbohydrates. Molecules of carbohydrates consist of atoms of carbon, hydrogen and oxygen. Theoretically to create carbohydrates magically adapted wheat may not even need anything from the soil, relying of water, carbon dioxide and Sun energy.

These 3 elements represent about 99% of mass of all plant life.

There is another important component for plant life, nitrogen, it's about 1% of mass. It is abundant in atmosphere but very chemically stable so plant's don't get it from the atmosphere. That's why various tree- or four-field systems include legumes - they have symbiotic bacteria that fixate atmospheric nitrogen into ammonia (NH3).

Phosphorus and sulfur are also used, but much less than nitrogen, less than 1% of mass.

Using magic "genetic engineering" it is possible to make wheat using atmospheric nitrogen directly and reduce reliance on phosphorus and sulfur.

So, basically, your new magically altered wheat can grow on sand. Or even require sand to grow. To avoid impact on the rest of the world the wheat may require a fertilizer that only magic desalinization can produce.

Your wheat may not be as good as "original" one because of low content of various minerals present in normal soil and absent in sand. It is much more efficient to fix it by adding necessary stuff to flour than trying to turn sand into soil.

Most of salts end up in the sea eventually. Your magic desalinization process can produce tons of salt. It can produce fertilizers and mineral additives for food.

You don't have to get deep in chemistry, naturally. "Magically altered wheat that grows on sand with fertilizers from sea water" looks fine to me. It appears that your story implies that these are new magic advancements no one thought about before. Adding magically altered wheat seems to fit it ok.

  • $\begingroup$ So you can grow crops in deserts just by throwing lots of water on the sand? Won't it all just seep into the soil and go to waste? Besides, the crops won't have any nutrients from the soil. Don't they need manure or fertilizers? $\endgroup$
    – Thales
    Commented Jun 25 at 12:24
  • $\begingroup$ @Thales. "Won't it all just seep into the soil" - it will make the soil moist, roots will get it and plant will use to build hydrocarbons. It will happen regardless of soil composition, that's just how it works. "the crops won't have any nutrients from the soil" - I explained why it is not necessary for 99.9% of plant mass and how to work around the remaining fraction of percent. In details. What kind of question is that? Did you read pasty the 2nd paragraph? $\endgroup$
    – D'Monlord
    Commented Jun 25 at 13:08
  • $\begingroup$ Your suggestion of just using magic to solve the is just not very useful, bud. I could have done that myself. I specifically wanted an answer that involves engineering. $\endgroup$
    – Thales
    Commented Jun 26 at 8:02

The short answer: canals. A lot of canals.

The long answer: I’m assuming this will be a state project instead of developed solely by individuals. First, develop large desalination facilities where many wizards will desalinate saltwater and put it in a large lake. Then, dig canals to the rest of the area. These should branch out so they make sort of a fan shape. These will have to run downhill, but you said topography isn’t a problem, so I’ll leave it at that. Also, you should put dams before each canal so you can control the flow of water depending on demand. Next, give every person the right to use the canal’s water by allowing them to dig canals off of it, and make sure that each person is only using what they need. This is important to prevent speculation and profit-seeking with this most valuable of resources. I’ll let you decide what the punishment is for breaking the law.

And that’s it. Really. You just need a way to distribute the water over a large area. After that, you can sit back and let your citizens do the rest.

(P.S. The reason “throwing water at it doesn’t work” in the real world is because water is a problem in arid areas. With infinite water, however, you can just throw water.)


If you want a science fiction based answer, then engineers would capture ice bearing comets from the planets rings or a near by asteroid belt and would drag them into a low orbit.

the comets would break apart above the designated areas and would shower down a mixture of vaporized water ice and simple organic molecules which would combine with material seeded into the clouds to form a nitrate rich mixture that would be carried down beneath the sand as the vapour condensed into water.

It would literally rain the building blocks of life down on to the desert.


Sodium polyacrylate

This polymere absorbs water. You can introduce it to the soil and it will absorb water there. This will prevent water from vaporisation and from going down, where plant roots can not reach it. Plant roots are capable of extracting water from sodium polyacrylate, root's mechanism of water absorption is stronger than that one in sodium polyacrylate. You can use water with fertilisers, it will be absorbed too.


Possible explanation; it could happen naturally.

Let's say that your Empire is doing these things because it predicted a close astronomical encounter in the future with a rogue planet or red dwarf.

This encounter slightly changes the planet's orbit and increases its tilt, which, over the course of about a human lifespan, will begin to green the desert by making it rain a lot more there, as monsoons reach further north. Agriculture can exploit this by adding fertilising substances to speed up the process of biomass accumulation in the soil, turning sand and rocks into fertile ground in decades rather than centuries.

See; https://en.wikipedia.org/wiki/African_humid_period


Sandy Dessert

What you want is a mobile, solar sinter robot. It Collects sunlight as an energy source and runs the sintering process, and sinters together glass structures. https://www.youtube.com/watch?v=ptUj8JRAYu8

Those glass structures collect moisture, provide shade, pump the moisture to the surface at night watering life- and thus provide niches in what is otherwise a mill made of dust milling life to dust.

What you also want is an underground 3d printer. It drills down 5 meters and generates a loam-like blob down there. Many blobs form a pan, that forms the basis for an underground basin that holds the occasional dew drop going into the ground.

Finally, sentries.. robots that guard this greenery buildup against the final boss of desertification. Nomads and endless goat herds that are at this point often nothing but status symbols of wealth. FPV robots can kill goat herds.

Rocky Desert

Rocky dessert, already has all of the above, but its hidden. There are small pockets, that stay relatively cool, still get light- and store water underground. What you need there, is a mapping robot, that is able to compute a simulation of days and find these "temperate" little places. Then you place seeds there. No, not you, a robot of course.


Once nature takes hold, it tends to create its own micro-climate that stabilizes things and allows it to expand.


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