Fertiliser burn occurs when you overfertilize your lawn, leaving large brown patches of dead or dying grass that, unless properly cared for, will likely not regenerate on its own. In cases where the grass is dead, the only thing you can do is adjust the soil concentration and replant your grass. If the grass still has life in it, there are things you can do to even out the concentration of fertiliser in the soil and save your grass.
Water the brown spots upon first noticing them to help drain the excess nitrogen out of the soil. Nitrogen is what causes the grass to die, and evening out the nitrogen content in the earth may save your grass.
Apply 4.54 Kilogram of powdered gypsum for every 100 square yards of damaged lawn. Gypsum binds to the salt in the soil and leaches it out.
Spray the gypsum-powdered lawn with water, allowing the water to soak into the soil, rather than running off.
Repeat the gypsum powder and water process until you begin to see signs of life returning to your grass.
Switch to an organic fertiliser once you see that your grass is starting to return. Organic fertilisers are longer lasting and will help restore lost nutrients that can increase the health of your grass without damaging it.