Lawn dying

[Jack54]

2 years ago a spot in my yard started to turn brown. It was in a round shape with a little green in the center. It then over a years time grew to 4 ft or larger. I removed all of it along with a couple inches of dirt. I then added 2 to 3 inches of top soil and laid new St Augustine sod. It was good for a season but has now over the winter and spring is brown with some green but betting worst.
I don't know what to do but dig it all out again. I live in Fort Worth, TX.

[applestar]

You said the round shape grew to about 4 feet diameter? How big was the circle originally? Was it perfect circle or more like a blob? Was the “little green in the center” any particular shape?

- When you dug out the old area, did it seem any different from surrounding area? Anything buried underneath, etc?
- is this area lower higher than surrounding area?

...I’m wondering if some kind of herbicide was spilled there — the kind that affects new/young growth rather than established/mature (sod) growth... or maybe there used to be a tree/shrub there that died and the fungus that is growing in the decaying roots is affecting the grass.... !! OR it was killed with systemic herbicide absorbed into the roots and now the herbicide is killing the grass?

[Jack54]

I have owned the house since new, 25 years. I have not spilled anything. When I dug the area up before I didn't notice anything different. It does have a sprinkler head almost in the middle. Not a perfect circle but pretty circular. It appears it now has the larger area and a smaller one starting up connected to the larger area. There is green grass but very thin and here and there. I tried attaching a picture, guess it didn't come through.

[applestar]

So maybe a fungal disease? It might be a good idea to disperse a lawn fungicide through the irrigation system?

[applestar]

...Use a siphon mixer/injector

— this is the kind I have, most often seen I think?
How Hozon™ Brass Siphon Mixers Work
http://hozon.com/how-hozon-works/