Written by: Dr. Steve Thompson, DVM - Director
Purdue University VeterinaryTeaching Hospital Wellness ClinicWest Lafayette, Indiana
Dog urine and feces can often be a frustrating problem related to lawn care. Small amounts may produce a green up or fertilizer effect while larger amounts often result in lawn burn or dead patches. While most burn spots will recover with time and regrowth, dead areas can be large enough in some cases to require reseeding or sodding. For homeowners who are also dog lovers, this can present a dilemma, particularly when one family member prefers the dog and another prefers a well-manicured lawn. An understanding of the interaction between dogs and the lawn can keep the yard (and family) at peace, not in pieces.
"Dogs Damage Lawns," would not be an attention-grabbing headline, because it’s so commonplace. So common in fact that a series of urban myths has arisen over what causes the damage, i.e., female dog urine is more acidic and therefore damaging than male dog urine. There are also ineffective and crazy techniques that people try to stop dog pee damage like adding tomato juice to the animal’s diet or baking soda to its water.
The fundamental problem with the presence of urine or feces on the lawn is related to the nitrogen content and concentration of these waste products. Dog urine, when produced as a waste product in animals, primarily removes excess nitrogen from the body via the kidneys. Nitrogen waste products are the result of protein breakdown through normal bodily processes. Carnivores, including cats and dogs, have a significant protein requirement, and urine volume/production varies due to size and metabolism. Urine is a more serious problem for lawns because it is applied all at once as a liquid, whereas feces slowly releases the waste products over time.
Young dogs of both sexes frequently squat to urinate. Leg lifting is often learned by male dogs around a year of age; castration or neutering does not seem to affect nature’s timetable related to this behavior development. While most male dogs will hike their leg and mark once they are over a year of age, a few will continue to squat when urinating. Female dogs may also mark, although less commonly than male dogs. Once dogs begin urine marking, they often utilize many and numerous scent posts resulting in numerous, small volume urination rather than large volume puddles.
Speculation on the actual cause of the lawn burn has resulted in numerous theories on what else in the urine may be contributing to the damage. Dr. A.W. Allard, a Colorado veterinarian, examined numerous variations in dog urine and the effects on several common lawn grasses. His results support the fact that volume of urine (nitrogen content) and urine concentration had the most deleterious effects on lawns. The pH of the urine did not have any variable effect nor did common additives designed to alter the urine pH
The grass types that are most tolerant of dog pee damage are grasses that have deep digging grass roots. Of the four grasses tested, Festuca sp. var. Kentucky 31 (fescue) and Lolium perrene (perennial ryegrass) were the most resistant to urine effects. In fact, the urine routinely produced a fertilizer effect on these grasses at diluted concentrations. Poa pratensis (Kentucky bluegrass) and Cynodon sp. var. Fairway (bermudagrass) were very sensitive to any urine concentration and severe burns resulted, persisting greater than 30 days after initial exposure to even four ounces of diluted urine. Even on the most urine resistant grass tested (fescue) urine concentration was a bigger problem than urine volume. Concentrated urine with volumes as little as 30 cubic centimeters (one ounce), caused lawn burn even on fescue grasses.
The best way to prevent dog pee damage in lawns is to promote deep digging grass roots. To do this the lawn should be mowed at 3 inches or taller. The reason for this is because grass roots will grow 3 times as deep as they are tall. Therefore, a lawn that is being mowed at 2 inches will have roots that dig up to 6 inches deep while a lawn that is being mowed at 3 inches or taller will have grass roots that dig up to 9 inches deep.
Another way to promote deep digging grass roots is to water the lawn deeply and infrequently. The best explanation on how to promote deep digging roots via lawn watering is to follow the 1-2-3-2-1 lawn watering technique. This technique is designed specifically to promote deep digging grass roots and to stimulate beneficial microbial activity in soils.
A great many dietary modifications for dogs have been tried, often based on home remedies or anecdotal experience. A veterinarian should always be consulted prior to making any dietary modifications, whether they include additions or subtractions from standard nutrient guidelines. As stated earlier, the pH of the urine has little or no effect on the urine damage to the lawn. The addition of acidifying agents, including nutritional supplements like D-I, Methionine (Methioform), Ascorbic Acid (Vitamin C), or fruit juices will have no benefit for this problem and may predispose the dog to an increased incidence of certain bladder stones. Likewise, alkalinizing agents, including baking soda and potassium citrate can predispose to other types of bladder stones or infections. The addition of any of these supplements has enough potential to cause harm, with limited to no known benefit for the lawn, and are not recommended.
When owners have reported successes, as is sometimes the case on internet forums, liquids likely improved the situation because the urine concentration after treatment was diluted. Safer ways to accomplish more dilute urine include feeding canned food, moistening dry food with water prior to feeding and adding salt or garlic salt to the regular food. One particular home remedy, tomato juice, likely has its primary benefit through both increased salt and water intake. While salt will make the dog drink more and dilute the urine, increased salt intake can cause problems for dogs with existing kidney or heart conditions. Owners should not alter their dog’s diet without consulting with their veterinarian.
Dogs with more diluted urine may have to urinate more frequently as well and need more frequent elimination opportunities. While specific breed differences haven’t been noted, smaller dogs produce less urine than larger dogs. Dogs with bladder infections often demonstrate an urgency to urinate and typically squat several times, leaving small amounts or drops each time. These dogs may be less of a problem for lawns than normal dogs who empty their whole bladder in one sitting. Dog owners who actually note that their dog’s urine is no longer causing the lawn to burn, without having made any changes, should have their dog examined by their veterinarian and a urinalysis performed to make sure there are no medical conditions causing this change.
The other option to consider besides diluting the urine is to reduce the amount of nitrogen waste being dumped in the urine. The average family dog doesn’t have the activity level that requires as high a protein level as most commercial maintenance dog foods provide. Although, dog food purchasing often reflects consumer perception that high protein equals better food, in fact moderate to low protein foods are often adequate for all but the most energetic, working and hunting dogs. When examining a food label, protein content must be compared on a dry matter basis and unfortunately, it is not like comparing apples to apples. Dry foods vary in how much moisture they have, so the protein percent listed can’t be immediately compared to all other foods. Canned foods will have a much lower protein percent listed than dry foods but also have much higher water content.
The quality of the protein also has an impact since some proteins are highly digestible, meaning less is dumped in the feces and possibly the urine, than other proteins. In general, the premium and super premium pet foods, available from pet stores and veterinarians, will have higher quality protein and more digestible proteins than standard grocery store brands. The higher digestibility translates into smaller fecal size as well. It is probably best to discuss individual pet needs with a veterinarian or nutrition consultant in the practice to determine what is the best fit, based on feasibility, palatability and economics. In many cases, if a dog food is currently providing good, overall nutritional support for the pet, diluting the urine by simply adding water to the food may be the easiest place to start.
Deep and infrequent lawn watering is the best way to promote deep digging grass roots. The deeper and more established the grass roots are in a lawn the less likely it is to suffer from dog urine damage. If you follow the guidelines in the 1,2,3,2,1 lawn watering technique this will help develop deep digging grass roots in a lawn, which will be less susceptible to dog urine damage.
Lawn burn, when mild, will often repair itself over time, especially in the case of the warm-season turf grasses that spread by rhizomes. Dark green spots and taller grasses may remain for several weeks. Sodding can be a quick way to patch severely damaged individual areas that would otherwise be invaded by weeds.
#1 - Water the lawn according to the 1-2-3-2-1 lawn watering technique.#2 - Mow the lawn tall - grass roots will grow up to 3 times as deep as the lawn is mowed tall. Mowing the lawn at 3 inches will promote grass roots to grow up to 9 inches deep.
#3 - Core Aeration - Soils that are compacted are more difficult to penetrate and soils that are loose allow grass roots to grow more easily.
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