help with my lawn please

[007agent]

About 4 years ago a the grass in the lawn started dying in a large ring.
Mushrooms have been growing in it. The grass either side of the ring is very green and healthy. We dug out a lot of the soil in the ring and re-seeded the bare patches. New grass grew but died the following year. Last year we again dug out the trench, filled it with topsoil and laid turf in the bare patches. All was fine all winter, but in the spring the grass the grass again started dying. We now have an even larger bare circle with mushrooms growing in the adjacent grass. Can anyone advise me what I need to do. The rest of the lawn is very healthy and green. It is mowed at least twice a week, and I do put down lawn treatments once per year. Any help greatly appreciated.

[JMR27]

Just had a look at our lawn book and this is called a grade a fairy ring and is a major problem. It says no water-on technique has proved reliable as the underground fungal growth waterproofs the soil. You can try iron sulphate (half an ounce in a gallon of water per sq yard) but the real answer is to remove the turf and topsoil to a depth of 1 foot. The area of excavation should extend to i foot beyond the inner and outer edges of the ring, and all the earth should be moved well away from the lawn, taking care not to spill any on the turf. Fill the hole with clean topsoil and then re-turf the area.

[JMR27]

'i foot' should read 1 foot

[maxi2]

The only time I had such a problem it turned out that the "ring" was around the site of a tree that had been removed. Removing the roos was the only solution.

[AlBags]

Yes .. you need to treat the soil underneath to kill the spores/threads, etc. Difficult job.

[Kathy46]

Jump in it and make a wish :-)

[007agent]

Many thanks jmr27 that is very helpful. It's true when you say the spores waterproof the soil, because when we have heavy rain, the water doesn't soak in as it does on the rest of the lawn, but sits on top in puddles. When we have previously dug out a trench we obviously haven't gone down far enough. Oh well, looks like we will be busy this weekend. Thanks again, much appreciated.