A combination of fungi and compost could make the lunar regolith more fertile and one day help astronauts grow crops on the moon, according to new research based on experiments with chickpea plants.
Future outposts on moon must be as self-sufficient as possible to avoid the high costs of constantly transporting supplies from Earth. If crops can be grown on the moon, it will be a significant step towards this.
The problem is that the dirt on the moon – what we call regolith – is not particularly good for growing plants.
Unlike soil on Earth, which is full of organic matter, regolith contains no microorganisms and no organic matter in general. And while it contains some important nutrients, it’s also full of toxic metals like aluminum, copper, and zinc. Also, it is not particularly permeable to water – a problem when you want to irrigate your crops.
So scientists set out to treat the lunar regolith to try and make it more conducive to growing plants in. This has led to a series of experiments. Now a team of researchers has discovered a new mixture containing organic materials commonly used for soil regeneration on Earth that increases the fertility of the regolith.
“Research is about understanding the viability of growing crops on the moon,” study leader Sara Santos of the University of Texas said in a statement. “How do we transform this regolith into soil? What kind of natural mechanisms might cause this conversion?”
When conducting experiments with lunar regolith, scientists use simulants, which are artificial mixtures designed to be as close to the real thing as possible. That’s because samples of real lunar regolith are rare and scientifically valuable.
In their experiment, Santos’ team added different concentrations of vermicompost to several samples of a simulant based on real regolith brought back to Earth by Apollo mission. Vermicompost is a compost produced by red wiggler worms that like to break down bio-waste, such as food scraps, hygiene products and cotton clothes, and recycle them instead of throwing them away.
To some of these samples they also added arbuscular mycorrhizal fungi, or AMF for short, while other samples only had AMF without vermicompost, giving a mixture of different amounts for contrast and comparison.
AMF is a fungus that is usually found in soil. It has many positive benefits, such as improving the circulation of nutrients in the soil while reducing the amount of toxic metals, and even producing a protein that helps bind soil particles together, reducing the amount of erosion that takes place.
Santos’ team grew chickpea plants in all of these samples. They also had some chickpeas growing in regular, terrestrial soil to use as a control to compare all regolith-grown chickpea plants to.
Over time, Santos’ team compared the growth of the chickpea plants in the different samples, and the quantity and weight of their seeds. They found that the chickpea plants only flowered and produced seeds in samples treated with both the vermicompost and AMF, and which did not contain more than 75% regolith. A higher concentration than this led to severe signs of stress in the plants.
But even below 75% regolith, things weren’t perfect. For example, compared to the control plants grown in terrestrial soil, the plants in the simulant produced fewer seeds. However, the individual seeds of these plants grown in simulant with between 25–50% vermicompost had a weight comparable to the control plants. Plants grown in simulant treated with AMF also had much greater dry shoot and root mass, suggesting that the presence of AMF aided the growth of the plants.
For now, the researchers say, it is not clear how suitable the chickpeas grown in regolith are for eating.
“We want to understand their feasibility as a food source,” Jessica Atkin, a Ph.D. candidate at Texas A&M University and lead author of the study, said in the statement. “How healthy are they? Do they have the nutrients the astronauts need? If they’re not safe to eat, how many generations until they are?”
Nonetheless, the findings bolster the idea that crops could one day possibly be grown in lunar regolith to help astronauts living in a lunar outpost. Indeed, the AMF fungi successfully colonized and survived the simulant, suggesting that terrestrial organisms may find a home in the lunar regolith.
By fine-tuning the soil regeneration strategies used here by Santos and Atkins’ team, it may even be possible to improve the fertility of the regolith, eventually turning it into a truly self-sustaining soil rich in organic molecules and microbial life.
The research is described in an article published on 5 March in the journal Scientific reports.
