Posted: 09/06/2016 at 18:37
It looks like your cactus is an Opuntia of some description. The yellowing is quite normal at or just below the soil line.
From your photo, the compost looks very wet and with a lot of fibre. Not a good choice for cacti.
If it needs repotting, just go one size up and use a specific Cacti compost. Top dress with a good layer of grit and don't over water
At this time of year, your cactus can go outside in a sunny position.....can remain outdoors until late summer/early Autumn ( depending on your location of course ).