How do you mean?-what are you growing in it?
Is there anybody there.....? there...there...Is that an echo?
I replace the top few inches with fresh compost, fertilizer of some sort depending what you're growing in the pot, seems to have worked well for me
I do the same as the Manic Slughunter. (Incredible name!, but descriptive.)
To revitalize your plot ,you need to dig some compost in ,Test soil to see what type it is ,and collect some seaweed (a little at a time) make a liquid fertilizer and the waste seaweed dig into the ground,dig comfrey into the soil too!
Why do people not check to see if there question has appeared-and what responses they get-at the moment still don't know what we are talking about--just guessing-it is like fishing in the dark