Tuesday, May 17, 2011

Dog Spots and Urine

If you see a lush spot of grass where one our four-legged friends has made a deposit of liquid nitrogen, you will know the lawn needs an application of nitrogen fertilizer.

 The best remedy for this problem is to fertilize with a nitrogen source. This will stimulate the grass into vigorous growth. The resulting green grass will help hide (i.e. mask) the dog spot. The amount of nitrogen to apply will vary depending on how deficient the lawn is of this essential nutrient but it is best to start with a small dose of nitrogen to correct such a deficiency. A half pound of nitrogen per one thousand square foot area of lawn is a good amount to apply if you have a cool-season grass lawn such as tall fescue, perennial ryegrass or bluegrass. Applying more than one-half pound of nitrogen per thousand square feet can result in excessive growth and the need to mow more frequently. Applying more than one-half pound per thousand can also lead to increased lawn disease problems. That is one-half pound of nitrogen not one-half pound of fertilizer.

To figure out the amount of fertilizer to apply for the one-half pound of nitrogen you need to know the percentage of nitrogen in the product. Nitrogen is the first number of three on the label. This number indicates the percentage of nitrogen by weight. Thus if the label says 20-0-0 that means this product contains 20% nitrogen by weight. Convert the percentage to a decimal – i.e. 20% = 0.20, then divide the number of pounds of nitrogen required by this decimal. For example if you want to apply one-half (0.5) pound of nitrogen, divide 0.5 by 0.20. The answer, 2.5, is the pounds of this product you need per 1000 square foot area of lawn to apply one-half pound of nitrogen.


The myth about female dog urine being more acidic and therefore more damaging than male urine, and the myth about reducing the damage caused by urine by adding tomato juice to the animal’s diet or baking soda to its water are just that, myths. The cause of urine burns on lawns (or bushes by male dogs marking their territory) is the amount of nitrogen in the urine and the amount of urine deposited. Before you try one of the numerous treatments said to be effective in reducing dog spots talk with your veterinarian. Treatments not approved by your vet can lead to bladder and other problems.

Another myth that doesn’t work is the use of gypsum to deactivate urine. Amending the soil prior to planting the lawn and aerating to improve the movement of water into and through the soil, however, does help reduce dog spot problems as they increase water movement into and through the soil and helps move the nitrogen below the point of deposition. This helps dilute the nitrogen concentration.

Grass can handle small deposits of urine, but when numerous deposits are made in the same spot, a dead spot surrounded by deep green lush grass will result. The nitrogen overload causes the center dead spot.

Tall fescue and perennial ryegrass are more resistant to the effects of large doses of liquid nitrogen with Kentucky bluegrass being quite sensitive. While Kentucky or Texas-hybrid bluegrasses are more susceptible to urine burns, they also recover faster than tall fescue or perennial ryegrass due to their sod-forming growth pattern.

These spots are not only caused by female dogs. Young dogs of both sexes as well as older male dogs squat when they urinate. Male dogs typically learn to lift their leg by the time they are a year old. If you have every watched a dog, he/she will make numerous small deposits of urine. While our four-legged friends can cause spots in our lawns they are still worth having around. Forget about the small things, or should I say spots, and enjoy spending time with your canine friends.

Nitrogen waste products are created during the breakdown of proteins by the kidneys and expelled in the urine. While about 95% of urine is water, about 2.26% are the nitrogenous waste products creatine, uric acid, ammonia, and urea [(NH2)2CO] with the latter being the highest percentage of the four. The content of the nitrogenous waste products in the urine depends on the amount of protein in the diet. The use of meat or other high protein treats increases the amount of urea that ends up in the animal’s urine. While some of the nitrogenous materials end up in the feces, these more solid deposits release nitrogen much slower than urine and thus seldom burn the grass.
Urea fertilizer common in agriculture is produced from synthetic ammonia [NH3] and carbon dioxide. You may have even purchased a bag or two of urea from a garden center or farm supply store for your own garden or lawn. Other than one being dry and other liquid, the urea is the same whether you buy from the store or collect it every time your pets (or you) urinate.

I read Captain Corelli's Mandolin a number of years ago and a paragraph on urinating in the herb garden struck me as a simple solution to correcting a nitrogen deficiency. This novel tells about the Italian and Germany occupation of the island of Cephallonia during World War II when nitrogen fertilizers were in short supply. Somehow the impression urinating on the herbs was common even when other forms of nitrogen were available.

As with any fertilizer application the rate is critical. Smaller applications spread out over the season would be more beneficial than larger doses which could burn roots and reduce production. The same guidance should be followed as to when to apply urine as if you were using any other nitrogen product.

If you figure the average person produces one-third gallon of urine a day, and it takes about 10 gallons of this liquid for each pound of nitrogen, it will take a month for one person to create one pound of nitrogen. If your friends and neighbors joined the club, you could accumulate a great deal more. You could even store what was produced during the winter for use during the summer. If more meat and high protein products were consumed the concentration of nitrogen would be even higher.
Urine has been used for many years to fertilize vegetables, herbs and other crops so it should be no surprise to read about its used in years past or even today. Don’t however look for me to follow through on this idea. I find using ammonium sulfate and blood meal to be just as easy to apply without the possibility of ending up in jail for indecent exposure. If this liquid form of nitrogen was collected in the privacy of your home and then applied through a hose-end sprayer as one does Miracle Grow and other liquid fertilizers jail time would be avoided.


  1. If you install artificial garden grass, this problem will be solved easily.