At the start of the experiment we mixed organic matter and green grass from another experiment (for the purists Lolium perenne L.) with the Mars and moon soil simulants. It should provide the crops with more nutrients and thus enhance growth. But there is more to it, much more. This is the fourth post in a blog series about experiments conducted by a team of ecologists and crop scientists from Wageningen UR in the Netherlands. The goal of these experiments is a proof of concepts for providing the first (human) Martians with own-grown fresh food. Make sure to read our first three blog posts!
Although there are nutrients available in the Mars soil simulant, the amount is rather low, especially in nitrate, which is essential for plant growth. By adding organic matter the grass can change that since nutrients can be released from it. But this needs some help, which is where the bacteria come in. They are able to ‘digest’ the organic matter and release the nutrients in the process. If it were not for the bacteria there would be no total breakdown of organic matter, not on Mars in a future greenhouse and not on Earth, where all organic matter would pile up covering the whole Earth, with no life left in the end. So bacteria are essential for a continuous crop growth on Martian soil. However, the function of over 90% of the soil bacteria is still unkown. Some may be harmful for plant growth and ideally you should leave them at home on Earth. Bringing bacteria will not be that difficult, as inoculates, but bringing the right ones will therefore be a challenge.
Can bacteria do the job on their own? In principle yes, but fungi could be helpful as well. They can also break down organic matter and they can, as well as bacteria, form symbiotic relations with the crops, to enhance nutrient uptake and thus growth. Are we then complete? I don’t think so. To help break down the large organic parts into smaller parts I would like to employ the worm (the common earthworm or Lumbricus terrestris). It literally eats soil and, within it, the organic matter. It uses parts of the soil and excretes the rest as small particles. The organic matter in the particles is also reduced to small parts and can thus be more quickly and easily broken down by bacteria. So I make a plea here for bringing worms to Mars (and the moon), as part of (small) ecosystems that should support plant growth.
Story contributed by Wieger Wamelink, a Senior Ecologist at Alterra.