Do you know if there's any knowledge on how much fertilization you'd need to bring in? Or: whether it actually makes sense to use Martian soil to grow things on? If it doesn't supply much, one might just stick to hydroponics...
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