Lawn fertilizer and dogs just don't mix. A contributor to a forum at the University of British Columbia Botanical Gardens put it this way: "Would you crawl on the lawn after application on your hands and knees and then lick your hands without washing them?" But dogs can do some serious damage to lawns in return by producing the very same chemical packed into most fertilizers.
Dogs and Lawns
Turf grass' most important need is nitrogen. The nutrient is not easily gathered from the soil or air --- it travels in molecules containing two tightly bonded atoms. Dogs love to urinate on lawns, particularly out in front of the house or in that spot that's just recovered from last winter's die-off. They deposit urea --- a chemical with available or "fixed" nitrogen. The reason that this habit kills grass instead of nourishes it is that urine contains such a high concentration of urea that it burns the grass and overdoses the ground under it. There's such an excess that very large dogs (or smaller dogs who favor the same spot repeatedly) not only kill large patches of grass but leave tiny crystals of uric acid salts on the surface.
Lawn fertilizers contain nitrogen (often in the form of urea), phosphates and potassium. The chemicals that carry these basic ingredients in most fertilizers are not toxic but they can irritate skin and cause digestive upsets, including diarrhea in dogs. Other ingredients are not so benign. Herbicides and pesticides in "weed and feed" preparations have been linked to an increased incidence of canine bladder cancer by researchers at Purdue University. Lawn services that apply liquid fertilizer can leave these toxins --- or traces of them from the preceding customer's application --- on a lawn, hence the warning to keep children and pets off the grass until it dries.
Organics and Compost
Organic fertilizers are not regulated materials. They may contain pathogens or traces of pesticides that are present in the source of the fertilizer, whether it is animal manure, compost or sludge. The source of that fertilizer, whether plant, animal or human, "is what it eats." Herbicides, pesticides and heavy metals travel through sources into the "organic" fertilizer made from their waste.
A sick dog --- or a sick lawn --- should be of concern to its owner. Both require expensive treatment to restore them to health. A dog with digestive upsets can make work for an owner and bladder cancer, although treatable, can be painful and fatal for the animal. Replacing soil and re-seeding a lawn or part of it is often the only option when Queenie is persistent in her elimination habits. Dogs do not produce useful lawn fertilizer, nor does the fertilizer from the garden center agree with their systems.
Try adding vegetables to the diet of a dog that is an unrepentant grass-eater or have the vet check for nutrient deficiencies. Try to convince King to pick a potty area that's covered with gravel. If he persists, try flooding the area with water after he "does his business." Scatter agricultural lime occasionally to counteract the acidity of urine and improve water penetration to wash the urine through the topsoil. Keep your dog from making himself sick by keeping him off the lawn until fertilizer has been completely watered in and the lawn is dry.