Coping with Dog Urine Spots

Dog urine and feces can be a frustrating lawn care problem. Small amounts may produce a green up or fertilizer effect while larger amounts result in lawn burn or dead patches. While most burn spots recover with time, dead areas can be large enough in some cases to require reseeding or sodding. Homeowners who are also dog lovers, are presented with a dilemma, particularly when one family member prefers the dog and another prefers a well-manicured lawn.

The presence of urine or feces on the lawn is related to the nitrogen content and concentration of these waste products. Urine, when produced as a waste product in animals, 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 animal size and metabolism. Urine is a more serious problem for lawns because it is applied all at once as a liquid fertilizer, whereas feces slowly releases the waste products over time. Since stools are usually solid, owners have the option of frequent removal. With more time for the waste to dissolve into the lawn, stools that are frequently removed, damage lawns less than urine.

The primary concern from urine damage to lawns is minimizing the nitrogen concentration added to the lawn at any single time. Female dogs, being less likely to urine mark and more likely to squat, are the primary culprits of lawn damage since they will urinate anywhere on a lawn and usually all at once. This results in a single nitrogen dump confined to a small patch of grass. The resulting brown spot often have a green ring around the outside. The nitrogen overload at the center causes the burn, but as the urine dilutes toward the edges, it has a fertilizer effect. This characteristic brown spot / green ring pattern has been called "female dog spot disease" by some horticulturists. As might be expected, lawns most susceptible to nitrogen burns are ones where standard fertilizers are maximized in the lawn. Homeowners making the extra effort to have a green lawn may be quite discouraged by their neighbor's dog damage or their own pet's potty residue.

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.

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 30cc (one ounce) caused lawn burn even on fescue grasses.

Dr. Steve Thompson, DVM - Director
Purdue University Veterinary

Continue: Prevention of dog spots

Also read: Diet Modifications