The answer to 'lawn fertilization turning brown' is that this is a common issue caused by over-fertilization or applying the wrong type of fertilizer. Symptoms include brown, dead patches in the lawn that can spread and worsen over time. The solution is to stop fertilizing immediately and adjust your lawn care routine.
If the issue is caused by over-fertilization, the best approach is to stop fertilizing and water the lawn thoroughly to flush out excess nutrients. You may also need to dethatch or aerate the soil to improve absorption. If the problem is due to the wrong fertilizer, switch to a more appropriate formula for your grass type and climate. In some cases, the lawn may need to be re-seeded or re-sodded if the damage is severe.