A common and sometimes frustrating lawn problem comes from damage due to dog urine and feces. Small amounts may produce a temporary green-up or fertilizer effect, while larger amounts can cause burned patches of grass that may take weeks to months to recover.

It may come as a surprise to some, but dog urine is actually more likely to cause damage than feces. There are several reasons for this. First, most dog owners will immediately "scoop the poop" if walking their pet in the neighborhood and clean up any in their own yard on a regular basis. The feces also contain a lower concentration of waste material compared to urine, and even if left on the grass for a while will take longer to produce the damage.

The main wastes found in urine are nitrogen containing products of protein digestion, which are rapidly converted to urea by soil bacteria. Urea (which is also the main source of nitrogen in most lawn fertilizers) is very soluble, and in high concentrations has the potential to burn plants very quickly. If the urine is eliminated all at once in one small spot, it becomes an overdose of liquid fertilizer and burns the lawn.

This urination pattern is mainly responsible for the observation that female dogs usually do more damage than males. Male dogs will characteristically release urine in small amounts to mark their territory, using numerous scent posts, resulting in many small urinations rather than one large puddle. However, if a young shrub or tree becomes a marking post it can suffer burns with repeated markings. Female dogs like to squat and release all the urine in one spot. Depending on how large the dog and the puddle, this can cause the burn and resulting brown spot. A larger area can be affected if the female always chooses the same spot to go. The brown spot that appears in the grass several days later will often have a green ring around the outside. The nitrogen overload at the center causes the burn, but the urine concentration is diluted toward the edges, resulting in the green fertilizer effect. This brown-spot-green-ring pattern should be called "dog-spot disease." Smaller dogs may not go enough at one time to actually burn the lawn, but can still cause the green spots in an underfertilized lawn.

Research has found that urine volume and nitrogen concentration are the main factors causing damage. The acidity or pH does not matter. Female urine is not more toxic than males'.

So what can dog owners do to lessen this blight on the land? First of all, continue to scoop the poop.

If your female dog is causing dog-spot disease in your own yard, there are several options that can lessen the symptoms. Simply watering down the area after she is finished or at least once a day will dilute the puddle enough. Training a young female to go in a designated area covered by gravel or mulch will avoid the problem.

If you regularly walk your dog to its business, be more aware of the potential damage to your neighbors' yards. Don't let your female dog always go in the same area of the same yard, and try to move big female dogs around a little during their urination.

Maybe the really sensitive dog walker could carry a bottle of water along with the plastic bag?