Ugly, brown patches on the lawn can be caused by several problems, but one that appears with regular frequency is when the lawn is burned by incorrect fertilizer practices. The brown spot may be only a few inches across or include much of the lawn. It is especially prevalent on new grass with a rudimentary root system. With a little knowledge, homeowners can avoid the problem or fix it when it occurs.
What is Burning
Fertilizer, at its most basic, is a chemical salt. Like all salts, fertilizers attract moisture. If an imbalance exists between the fertilizer and grass, then moisture is drawn out from the grass stems and roots and dries them out. As the grass dries and dies, it leaves large brown patches on the lawn.
Following a few simple rules will help prevent fertilizer burn. Fertilize at the right time of the year--if the temperature is too cold the fertilizer will remain in the soil and draw moisture. Do not overfeed with excessive fertilizer, or distribute in the heat of the day. Use a spreader for equal distribution and water it in thoroughly. Do not use fertilizer on a lawn with excessive thatch until the thatch is cleared away.
If caught soon enough, heavily watering the affected area should wash the excessive salts away. If the burn has affected the roots, planting new grass seed or laying sod are the only options.
Using insoluble nitrogen fertilizer reduces the risk of burning. If a fertilizer manufacturer includes insoluble nitrogen as an ingredient it will be listed on the bag as a percentage of soluble verses insoluble nitrogen. The greater the percentage of insoluble nitrogen the better.
Another way of preventing burning is to use the yard's natural resources. Mulching the grass and leaving it on the lawn can provide up to 25 percent of the nutrition needs without burning.
Many gardeners believe that using only organic fertilizers will prevent burning on grass, but this is not true. Excessive nitrogen in any form will cause a chemical salt imbalance and injure the grass tissue. It may take longer for the burning to show, but if a lawn is heavily fertilized with organic material and then turns brown in the heat of summer as soil bacterial becomes more active, burning is a logical suspect.