Question
Northern Shenandoah Valley in VA.  Variety of fescues.  2 years ago a wheel fell off my fertilizer spreader and spilled fertilizer on the grass, burning out an area about 1 foot in diameter. I cleaned up what I could and later that year raked it out and mixed in some topsoil and reseeded the spot. The grass has since filled in, but left a ring (about a 6-inch band of dead grass around the spot.  The ring (circle) continues to get larger (bigger diameter) with good grass inside the circle.  The diameter is presently about 8 feet. I have again raked it out but it still continues to get bigger (larger diameter).  Any thoughts on how to stop the progression?  Could it be some other problem not related to the spill itself?

Pretty soon it will exceed the size of my lot and will become my neighbors problem (HA HA).

Answer
Hi George,

A fertilizer spill from two years ago is most likely NOT a factor in a lawn appearance problem you describe.  Time, watering, and zillions of microbes in the soil have converted all the salts of the spill into harmless metabolites by now.

When, a soil is particularly 'rich' in nitrates, as can happen with a fertilizer spill,... or an animal effect in the lawn,...certain species of FUNGI can get started in the soil. Any highly fertile soil or one which was once a feeding ground for cattle or horses, etc., can have fungus out-breaks due to all the residual organic matter in the root-zone.

One variety of these fungi is commonly called the 'Elf or Fairy Ring' fungus.  This can persist off and on for years in the lawn, causing a dead-ring of turf-grass. Note that these circular areas usually will also have periodic out-breaks of the associated 'Mushroom' growths.  Perhaps, you have not noticed these in the lawn or maybe conditions have not yet been good enough for the under-ground part of the fungus to produce these 'top-side' structures.  If and when they do pop-up in the ring, be sure to collect and destroy them before they can make SPORES to spread.  Here is more about 'Fairy-Rings' in lawns:
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About Fairy-Rings in Lawns:

"Fairy Rings" are due to the FUNGUS Marasmius oreades.  A ring of grass around bright green spots starts to turn brown and die; a circle of mushrooms usually develops around the perimeter edge of the infected area.  These often occur following an extended rainy/damp period.

 A sure eradication technique is to excavate-out the diseased area to a depth of two feet and diameter of one foot around the infected  patch; then fill in and replant the the area.  However, if spores have had a chance to develop-produced eradication may be much more difficult.

 Microscopic spores are the "seeds" of Fungi like mushrooms and Toadstools, etc.  These are carried everywhere by the wind and air currents; some are major concerns for allergy sufferers.

 The spores can settle and a new colony will grow where conditions permit.  Usually this is a cool-moist and organically rich substrate or soil.

 Mushrooms and Toadstools and other Fungi which pop-up sometimes it seems over-night, all have two basic parts:
a subterranean root-like, or fine-hairy web-like, growth called a "MYCELIUM," and the upper reproductive structures (mushrooms) we see on the landscape.

 If you harvest these upper structures rapidly before they can produce the many thousands of sub-visible spores,  you can do much to prevent future out-breaks in your lawn and your neighbor's as well.

 The mycelium will die-out once dry conditions prevail.
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REMEDIES:

 You can suppress the growth of Fungi by watering affected areas with a solution of one ounce of IRON SULFATE in three gallons of water applied at the rate of about one gallon per square yard. Iron Sulfate is often found at garden supply stores.

 Let your top-soil become "Nitrate Hungry" between fertilizing by permitting it to fade in greenness; this will make it difficult for any fungus to grow and will also benefit the grass plants proper.

Note;  Some Toadstools and "Shelf-Fungi" will pop up annually where there is a source of rotting wood.  These are generally harmless to growing trees and lawns and can be ignored.   
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 Be sure to properly dispose of all un-identified fungi, and keep pets and children from contacting them; some fungi are so toxic they should not even be handled without using disposable plastic gloves. Even a well informed Mycologist sometimes can't easily know a "safe" mushroom from an edible one without using a microscope.
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With a good fertile-loamy well draining top-soil, best quality hybrid grass type(s), 1-3 inches of water per week, plenty of sun-light, ...almost anyone can have an excellent lawn with a minimum maintenance effort.
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I Hope this has answered your question(s)!

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