This may be a stupid question, but can anything be planted in Martian soil, even if the atmosphere was corrected? I always assumed not.
Sure the pressure is 0.6% comparing Mars/Earth but the CO2% is 0.04% when comparing Earth/Mars.
In other words the partial pressure of CO2 on Mars is actually higher than on Earth. Which is great for CO2 breathing plants. If the temperature was raised a plant would have more CO2 available even with the much lower pressure than on Earth.
Indeed experiments with 95% CO2 (matching Mars) and 6millibars pressure (matching Mars) and with martian soil showed that Potato's grow fine. https://cipotato.org/blog/indicators-show-potatoes-can-grow-...
The only adjustment was temperature!
25ml of liquid water takes 3 hours to completely boil off under vacuum. Less if the water is mixed in with other substances (eg. soil). The inner structure of the plant itself is capable of trapping water to an even greater extent. To the point where water directly boiling off the plant directly isn't significant.
Note that this was simulating asteroid conditions. Mars is slightly better at retaining water since it has slightly more pressure. This is why it's pretty likely that we're seeing flowing water on Mars each summer: https://www.nasa.gov/press-release/nasa-confirms-evidence-th...
You'd have to fertilize the soil of course, but fundamentally plants don't need that much to grow. A lot of hydroponics use a completely inert "gravel" like substance and just wash a nutrient solution through on occasion.
It might not all be in amounts easily scavenged, but they're mostly there.
[0]: https://www.nasa.gov/feature/can-plants-grow-with-mars-soil