If you want to maintain a healthy lawn, avoid exposing it to products that contain uric acid. If your goal is to kill off a lawn in order to install a new one or replace it with something else, treating it with healthy doses of uric acid is a good way to kill the grass down to the roots and make it easy to remove.
What is Uric Acid?
Uric acid occurs naturally in the bodies of people, dogs and other mammals and is excreted in waste material. Uric acid contains large amounts of nitrogen and salt, materials mammals need to survive, but only up to certain point. Whatever the body doesn't need is excreted. Waste material contains varying amounts of uric acid. Uric acid is not harmful in small amounts, but can damage grass and other plants in larger, more concentrated doses.
A common source of uric acid for many lawn owners is the family dog. Dog urine contains high levels of uric acid, and dog owners with lawns are likely to see the familiar brown spots caused by dog urine. The problem is more common with female dogs that squat to urinate, since they deposit large amounts of urine in a concentrated area. Cat urine also contains uric acid, but few cats produce enough urine to do damage to grass. Fertilizer and manure also contain uric acid and using too much on a lawn is a sure way to kill it, which is why fertilizer labels contain warnings cautioning against overuse.
What Causes the Damage?
Uric acid damages grass because of its nitrogen and salt content. The salt coats the indivdual blades of grass and slowly leaches water from them, causing the grass to eventually die from dehydration. Nitrogen is less harmful, but an over-abudance of nitrates has the same effect on grass and can kill it by draining its water supply. A hot dry climate can accelerate this process and allow uric acid to damage or kill a lawn faster.
Though all types of grass are susceptible to damage from uric acid, some are more vulnerable than others. Kentucky bluegrass and perennial rye grass are two types that are easily killed off by uric acid. Hardier types such as Bermuda grass and St. Augustine grass are not damaged as easily and grow back more quickly when they are exposed to uric acid. Small amounts of dog urine don't contain enough uric acid to damage grass and can actually help it grow faster due to the additional nitrogen. The grass in the exposed area will grow taller and darker than the surrounding area.
Killing a Lawn with Uric Acid
The best way to get rid of a lawn using uric acid is through the liberal use of fertilizer. Choose any lawn care fertilizer and dose your lawn with three to four times the amount recommended on the label. Wait a few days, repeat the process, and the lawn will be on its way out. The combination of the salt and nitrates in the uric acid will dehydrate the leaves and infiltrate the roots with a buildup of sodium, bicarbonate and boron, making them unable to absorb nutrients.