its a ring of fungi and the ring will get bigger and bigger as it spreads and takes out of the soil what it needs . i dont think you can do a whole lot about it realy but i may be wron

Have you got any fungi growing?, i dont think there is anything on the market for this, some years its worse than others i find but it never goes away, digging out the ring is rather pointless as trying to get rid of the fungal spores is impossible, i tried the same as you many years ago for a client who insisted on digging the ring out and adding new soil and turf, i explained the situation and once completed it was not long before it returned it was a futile excercise.

The problem is that the main part of the fungus is well underground and is a network of fine white threads called mycelium. If you replace the turf the mycelium remains untouched and will carry on as normal. You are unlucky that you have a ring of dead grass - often you get a ring of darker green. If you keep your eye on it during the autumn you should see a ring of small brown toadstools which are the fruiting bodies of the fungus. As it isn't going to go away would it be feasible to make a flower bed where the ring is?

i thaught it was hard to get rid of but i wasnt sure . thanx for that everyone .

Thank you everyone for your replies, I hope this doesn't mean it will spread to the whole lawn, that would be a disaster because it would mean I couldn't even replace it if the fungus is deep down and cannot he cured. If I made a small flower bed where the ring is, as Steragram advised, wouldn't the fungus infect the flowers? Thanks again for all your advice.

the fungus would hardly if at all show in a flower bed thow as the ring gets bigger then so your flower bed will have to follow . it should just grow out bigger and bigger and the inside should recover .

But it only gets bigger very slowly.

so is life some things you got to lurn to live with realy .