In an effort to determine the best crops for this extraterrestrial agriculture, NASA is working with astrobiologists with the goal of establishing human outposts on Mars. In order to optimize yields under these particular circumstances, scientists are investigating novel planting strategies. An investigation into the possibility of increasing crop yields on Mars through intercropping—the long-standing practice of cultivating several crops near to one another—was recently published in PLOS One.
Simulating the Martian Landscape
Long-term human habitation on Mars depends critically on a reliable food supply. Although the inventive techniques used by the fictional astronaut Mark Watney in “The Martian” are fascinating, more workable solutions will be needed for actual Martian colonists. To find these answers, scientists are simulating the Martian environment on Earth. Mars has an atmosphere that is 100 times thinner than Earth’s and is mostly made up of argon, nitrogen, and carbon dioxide. Future colonies on Mars most likely will live in greenhouses under pressure that simulate Earth’s atmosphere by providing just the right amount of carbon dioxide, nitrogen, and oxygen.
“The optimal “Martian environment” is essentially just a greenhouse with regulated temperature, humidity, and gasses,” says co-author of the study Rebeca Gonçalves, an astrobiologist at Wageningen University & Research in the Netherlands.
Rebeca Gonçalves and her colleagues built greenhouses at the university to replicate the growing conditions on Mars in order to conduct this experiment. They assessed crop performance in a model of the loose, stony Martian surface material known as regolith. Sand and regular potting soil were used as control groups. To improve water retention and root development, organic Earth soil and nutrients were also added to the sand and Martian regolith samples.
Selecting Suitable Species
For this mock Martian farm, peas, carrots, and tomatoes were the selected crops. It was shown in a 2014 study that they could survive in Martian regolith. Gonçalves points out that although their potential for growth was known, their main concern was with how intercropping and companion planting might increase crop yields. There is also substantial nutritional value in these three options for upcoming colonists.
“We selected them for their rich antioxidant, vitamin C, and beta-carotene content,” says Gonçalves. “This is crucial because these nutrients are lost entirely during food dehydration, the primary method for supplying food on space missions. Therefore, cultivating fresh produce rich in these nutrients is essential for a Martian colony.”
It’s interesting to note that these crops are excellent companion plants because they also display complimentary traits. As legumes, peas “fix” nitrogen, which is a crucial component of the intercropping system. The process by which some plants and bacteria transform atmospheric nitrogen into ammonia, which is useful for plant nutrition, is known as nitrogen fixation. Consequently, this helps nearby plants and lessens the requirement for additional fertilizers. Gonçalves claims that doing so maximizes the use of resources for plant growth on Mars.
“Carrots were chosen to improve soil aeration, thereby enhancing water and nutrient uptake by companion plants,” Gonçalves explains. “Tomatoes were included to provide shade for the temperature-sensitive carrots and offer climbing support for the peas.”
Yielding Results on the Red Planet
In the Martian regolith, all three species grew fairly well, yielding more than half a pound of produce with little additional fertilizer. Significantly, tomatoes grown in the intercropping arrangement with peas and carrots performed better than control tomatoes grown alone. Both biomass and potassium content were higher in the intercropped tomatoes.
Nonetheless, it seemed that intercropping in this artificial Martian regolith reduced the yields of peas and carrots. Grown alone, these plants did better. The team hopes to improve the way the simulated Martian regolith is treated in subsequent trials in order to possibly boost intercropping yields and provide carrots and peas with comparable benefits.
“The success observed for one of the species is a significant finding that paves the way for further research,” remarks Gonçalves.
The beneficial impact of intercropping in the sandy soil control group also caught the team off guard. Two of the three plant species that benefited from this technique indicate possible uses for Earth’s agricultural systems. Sandier soils are becoming more common due to climate change, and this study adds to the continuing research into how intercropping might help address this problem.
Goal number one for the team’s upcoming research project is to develop “a completely self-sustaining system utilizing 100% of local Martian resources.” Future Martian colonies would become much more financially viable as a result, lowering their reliance on resupply missions.
“If we can unlock the secret to regenerating poor soils while developing a high-yielding, self-sustainable food production system—exactly the goal of Martian agriculture research—we will have found a solution for a lot of the issues we are having here on Earth as well,” concludes Rebeca Gonçalves.
