Growing potatoes on Mars
PHOTOGRAPH COURTESY OF 20TH CENTURY FOX

How To Grow Organic Potatoes On Mars

A fictional survival story set on the red planet has shed some light on organic potato gardening techniques.

September 3, 2015

Lasers, explosions, trippy space scenes: Next month’s theatrical release of The Martian, starring Matt Damon and Jessica Chastain, has is all, plus (wait for it) potato farming. On Mars. Yup. 

Based on the novel by Andy Weir, The Martian features Mark Watney, a mechanical engineer, botanist, and DIY tinkerer who is on an extended Robinson Crusoe-esque stay on Mars. To survive, Watney takes everything he knows about growing all-natural, all-organic potatoes on Earth and tests it out on the red planet to keep from starving. 

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Related: 7 Ways To Plant Potatoes

The novel goes into great detail about Watney’s techniques, effectively (and factually) teaching readers how to grow spuds on whatever planet they’re on. Here’s what we learned.  

Bacteria Allows Soil To Sustain Plant Growth

At the beginning of the novel, Watney is sent to Mars to study how things grow in the planet’s dirt.

Martian soil has the basic building blocks needed for plant growth, but there’s a lot of stuff going on in Earth’s soil that Mars’ doesn’t have.

For example, bacteria, which cycles nutrients in the soil. In general, beneficial bacteria are usually aerobic, requiring oxygen to survive. When bacteria is introduced to soil that’s depleted, it will spread and breed (similar to an infection). 

If your garden soil seems dry and low on nutrients, mix in a good healthy layer of compost.  Let it sit for a week or two before working in it, to allow the nutrients in the compost to spread out into the old garden soil.

Related: Make Fertilizer Faster By Making The Ultimate Compost Bin

Human Waste Is A Readily Available Source Of Fertilizer

Watney opts to use his waste to give extra macronutrients that are missing from the Martian soil.

Biosolids are not normally used in all practices of agriculture, mostly because of the variety of diseases that can be spread if it’s used improperly. There is a lot of debate on this topic (Is People Poop Good For Plants?). Some commercial composters boast that biosolids are rich in plant macronutrients, like nitrogen, phosphorous, and potassium, while those opposed to the use of biosolids warn that they can contain heavy metals, pathogens, pharmaceuticals, and pesticides.

Growing potatoes on Mars
PHOTOGRAPH COURTESY OF 20TH CENTURY FOX

Potatoes Can Be Planted In Just 4 Inches Of Soil

In planning his space garden, Watney decides to dedicate the entire 92 square meters of floor for planting potatoes. Potatoes can be successfully planted at a depth of 4 inches, so he brings nearly 10 cubic meters of Martian soil indoors.

Watney’s only tool to accomplish this vast excavating mission is a tiny shovel that was originally intended to collect soil samples.  If you’re planning on moving a large amount of dirt to a new garden area, do NOT go the Mark Watney route.  Invest in a solid garden shovel and a wheelbarrow if you’re the DIY type, or you can rent a small backhoe (or pay your local farmer friend to bring theirs over. Beer payments are often accepted among friends).

You Can Make A Planter Box Out Of Spacesuits!

It takes Watney several weeks to cover the floor in dirt. To keep the soil from falling all over the place, he uses blankets and uniforms from his departed crewmates to serve as temporary planter box edges.

Think of it as another way to upcycle old raincoats.  Or DIY Raised Garden Beds

The Secret To Huge Potato Harvests Is In The Cutting Of The Seed Potato

Watney starts out with 12 potatoes, sent up to Mars with the intentions of being used in a Thanksgiving meal with the entire crew. He cuts each potato into four pieces, making sure each piece has at least two eyes. He then sits them out for a few hours to harden, which effectively lets the 48 seed potatoes develop a protective layer against diseases before they go into the ground to form new tubers. About 40 days later, he collects a large harvest, grown from the original 12, something even Earthlings can pull off. 

Growing potatoes on Mars
PHOTOGRAPH COURTESY OF 20TH CENTURY FOX

You Can Grow A Thousand Potatoes, But If You Don’t Store Them Correctly, Your Efforts Are For Nothing

On Mars, all you need to do to store potatoes is to toss them outside. Most of the water would be sucked out by the near-vacuum, and what’s left will freeze solid. Any bacteria will die screaming.

Related: How To Build A Root Cellar

On Earth, however, you’re going to want to store them in a root cellar.  If you only have a few spuds, and you plan on using them within a few weeks, storing them in a paper bag or a burlap sack is a great alternative. Just be sure to store them out of direct sunlight, preferably a cool space that gets decent ventilation.

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