Ginseng ficus with one soft squishy trunk

[Yopo]

Hello everyone. I bought this ficus from a local store I didn't know that squishy trunk is a bad sign... anyways one of the three roots is squishy I tried to peel it off and it got removed easily. Inside it has the color in the picture. The other two are healthy. The plant is not losing leafs. It is growing new ones. I noticed also that the ground retains water more than three days and it is muddy in some places.
Should I add some clay balls or gravel and repot it ?
Can I cut the rotted trunk since it has three and the other two are healthy ?

 

[Crazy Diamond]

That is root roting, probably the soil is kept too wet and dont drain good, it needs a repot also you need to eliminate all the black dead tissue until you find the green cambium

 

[Yopo]

Thank you for your response I will repot it. May I ask how can I eliminate the dead tissues ? Should I cut it from the outsides with a razor blade untill I reach the green cambrium ?

 

[Shibui]

Most of us would call that a root rather than a trunk.
Definitely a problem that could affect other roots if it has not already. Caused by soil staying too wet. Most growers now use a potting soil with larger particles so the roots are not always wet and have better air.
The entire root is probably dead now. Cut off any obviously dead parts then continue to cut a little at a time until you see healthy cambium under the bark. Seal large cuts to help the bark heal over the wounds. Branch cutter is best to cut through large roots and branches but secateurs may do the job or a sharp knife. Not sure that a razor blade will be strong enough to cut right through that root.
No indication of what part of the world you are in. Ficus can be repotted in warmer weather and can tolerate large root reduction if needed.

Please add a location to your profile so you get better advice based on your part of the world.

 

[ShadyStump]

YIKES!
That soil has got to be at least as bad as the worst soil I've ever personally put a tree in, and I've tried some doozies.

If you're in the northern hemisphere, now is a great time to repot, in the heat of summer when the tree is actively growing. Like has been mentioned, cut off the rotten section and clean away anything rotten left behind. Be aggressive with it, the tree will be fine.
You can get a cheapo bonsai soil in many garden shops, otherwise regular potting soil will do allot better than the stuff it's in.

Let us know how it turns out.

 

[Yopo]

I have cut the dead root and I have changed the soil. I have bought one for bonsai trees and also a fertilizer for green plants and ficus. I have found that only that root is affected. The other ones are healthy and not squishy. I added also clay balls and now the pot drained water properly. The previous soil was muddy and so wet taking into consideration that it was not watered for three days. Thank you all for your help. I appriciate it. I will provide an update in a week since the ficus have new leafs. Hopefully it will make it.
And I live in north Africa in a coastal city ( we have enough humidity) and the weather now is min 20 degrees Celsius and max 26 degrees.
Again thank you all for your advices