For future humans to survive long periods on Mars, growing food on the planet is a must.
It would be too costly and risky to rely upon rocket deliveries to meet the food needs of colonists. With this in mind, scientists are exploring ways to improve space farming.
At Wageningen University & Research in the Netherlands, researchers work in a controlled greenhouse. They have identified a way that could improve crop production in simulated Martian soil, with different crops grown together. The method is called "intercropping.” It was first invented by ancient Maya farmers in what is now Central America.
In their experiments, the researchers grew cherry tomatoes, peas and carrots together in small, round containers called pots. Tomatoes grown in this way produced about double the amount of tomatoes grown alone - or "monocropped" - in the same simulated Martian soil. The tomatoes were also bigger. They flowered and matured earlier, gave more fruit per plant and had thicker stems.
The amounts of peas and carrots did not increase with intercropping.
Rebeca Gonçalves is an astrobiologist and lead writer of the study published on Wednesday in the publication PLOS ONE. She said the research is the first time the intercropping technique was used in space soil.
"And the fact that it worked really well for one out of the three species was a big find, one that we can now build further research on,” Gonçalves added.
The crops were grown in simulated Martian regolith, a soil with no organic matter. Created by researchers from the American space agency NASA, it is a near-perfect physical and chemical match to real Martian soil.
The researchers added useful bacteria and nutrients. They also controlled the gases, temperature and humidity inside the greenhouse to match conditions expected in a Martian greenhouse.
For now, human bases on Mars are only seen in movies. But NASA, for example, is developing ways to send people to Mars in the 2030s.
"Mars is really far away. A flight now would take about nine months. If you want to live there as humans, you will have to grow your own crops at the site," said study co-writer Wieger Wamelink. He is a plant ecologist at Wageningen and head of B.A.S.E., a company that develops lunar and Martian greenhouses.
"Flying in food is very costly and also vulnerable… Our main goal is to use as much as possible from the resources at the site," he added.
Intercropping involves growing plants with properties that could help each other grow. The method makes the best use of resources including water and nutrients.
The researchers said the tomato plants in intercropping may have benefited from being close to the pea plants. That is because the peas are good at turning nitrogen from the air, with the help of bacteria introduced into the soil, into an important nutrient.
The carrots produced fewer crops from intercropping and the peas had no change, Gonçalves said.
"It is very important how you select the crop species that you combine, because the tomato did profit from the peas, but the carrot most certainly did not. This was probably due to lack of light. The tall tomato and pea plants did out-compete the carrot by taking light from it," Wamelink added.
Overall, the tomatoes, peas and carrots grew well, though not as well as in Earth soil in the same greenhouse.
I’m Dan Novak.
