Hello. Two years ago I purchased a healthy 25 year old Chinese Elm.

I have been looking after it quite well and it seems to be growing fine.

I have not re-potted this tree as firstly I don't know how to do it and secondly I'm not sure if it needs it.

There are some large cracks appearing in the soil and I'm wondering if this is a sign of over-watering, or another issue?

Thanks

Poor substrate in combination with poor care. The soil is very dried out.
What is the fluorescend tube sticking out of the ground?

The soil is actually quite most to touch but obviously it could have been too dry quite recently.

The plastic item is a plant drip feeder which I used this year (spring time only) to help it grow:

Something like this:
i.ebayimg.com/thumbs/images/g/EGsAAOSwax5Yx8jz/s-l225.jpg

Should I re-pot the tree and take better care of the soil, ie don't over water, don't let it get too dry etc.?

Is the plant pot-bound? If a bonsai's pot is full of roots, the roots start pushing the base of the tree up. This might be causing the cracks. How long ago was it re-potted?

Also a couple of things: Certain soil "cracks" more than others when they are dry. You can see this in nature when clay dries, it cracks. Clay has virtually no organics, so make sure when you re-pot that you are using soil with enough organics to hold the moisture, but enough inorganics to allows for good drainage.

Another observation" Your moss seems to be drying, declining, or dying. Do the cracks go beneath the moss? It appears the moss around the feeder is in better shape either to do with it receiving better nutrients or simply more moisture. I hope this helps

Cheers!.

Ok so I've taken the tree to a nursery and had it re-potted.

I purchased the tree online. The tree was not wired so it may have been pulling upwards.

I was also informed the tree had only basic compost and not the correct mixture for the tree to thrive.

£30 re-pott and we go again

I have an chinese Elm in my house too.