There's a persistent myth among dog owners that dog poo is actually good for the lawn — a natural fertiliser, if you will. We hear it all the time: "Just leave it, it'll break down and feed the grass."
Unfortunately, the science tells a very different story. Dog waste is not only bad for your lawn — it can actively damage your grass, contaminate your soil, and create serious health risks for your family and pets.
The Nitrogen Burn Problem
The most visible damage from dog waste comes from nitrogen overload. While nitrogen is an essential nutrient for grass growth (it's the main ingredient in most lawn fertilisers), dog waste delivers it in concentrations that are far too high.
Here's the difference:
- Lawn fertiliser: Carefully balanced nitrogen, phosphorus, and potassium, applied evenly across the lawn
- Dog waste: Highly concentrated nitrogen dumped in one spot, along with salts and acids
The result is what turf specialists call "nitrogen burn" — those distinctive yellow or brown patches you see in lawns where dogs regularly do their business. The grass directly under the waste gets scorched by the excess nitrogen, while a ring of darker, lush green grass grows around the edge where the nitrogen has diluted to beneficial levels.
Dog urine causes the same effect, which is why you often see circular yellow patches throughout dog-owning households' lawns. The combination of urine and faeces creates a double dose of concentrated nitrogen that New Zealand's popular grass varieties — like fescue, rye, and kikuyu — struggle to handle.
The Bacterial Reality
Beyond lawn damage, the bacterial load in dog waste is genuinely alarming. Research has shown that a single gram of dog faeces contains an average of 23 million faecal coliform bacteria. To put that in perspective, that's roughly the population of Australia in a piece of waste smaller than your fingernail.
Common bacteria found in dog waste include:
- E. coli: Can cause severe gastrointestinal illness in humans
- Salmonella: Particularly dangerous for children and elderly people
- Campylobacter: One of the most common causes of food poisoning in New Zealand
These bacteria don't just sit on the surface. Rainfall and irrigation wash them into the soil, where they can persist for months. Every time your kids roll around on the grass, every time you walk barefoot to hang out the washing, you're potentially coming into contact with these pathogens.
Parasites: The Hidden Threat
If the bacteria weren't enough, dog waste also carries parasites that can survive in soil long after the visible waste has disappeared:
Roundworm (Toxocara canis)
Roundworm eggs can survive in soil for years. In humans, ingestion of these eggs can cause toxocariasis, a condition that particularly affects children. Symptoms range from fever and fatigue to, in rare cases, vision impairment. New Zealand has documented cases of toxocariasis in children, making this a real concern for Kiwi families.
Hookworm
Hookworm larvae can penetrate human skin directly — no ingestion needed. Walking barefoot on contaminated soil is enough. They cause a condition called cutaneous larva migrans, characterised by intensely itchy, winding red tracks on the skin.
Giardia
Giardia is a protozoan parasite that causes severe diarrhoea and dehydration. It's highly contagious between dogs and can also infect humans. Giardia cysts can survive in moist soil for months, especially in Auckland's temperate, humid climate.
Cryptosporidium
Another protozoan that's resistant to many common disinfectants. It spreads through contaminated water, which is why dog waste near waterways or drainage is particularly problematic.
How Long Does Dog Poo Take to Break Down?
Many people assume dog waste disappears quickly. It doesn't. Under average New Zealand conditions, dog faeces takes 9 to 12 months to fully decompose. During that time:
- Bacteria and parasites remain active in the soil
- Nutrients continue to leach at damaging concentrations
- The waste attracts flies and other pests
- Rainfall washes contaminants into surrounding areas
In Auckland's wet winters, the breakdown process can slow further, and rain events spread the contamination over a wider area of your lawn and garden.
Impact on Soil pH and Health
Healthy lawn soil in New Zealand typically sits at a pH of 6.0 to 7.0 (slightly acidic to neutral). Dog waste is acidic, and regular deposits can lower soil pH below the optimal range for grass growth.
Acidic soil leads to:
- Poor nutrient uptake by grass roots
- Moss and weed invasion (they thrive in acidic conditions)
- Reduced earthworm activity (earthworms are essential for soil aeration)
- Compacted, unhealthy soil structure
Over time, areas of your lawn that are regularly used as a toilet can become so degraded that re-seeding or re-turfing is the only solution.
Lawn Recovery Tips
If your lawn is already showing damage from dog waste, here's how to start the recovery process:
1. Remove All Waste First
Before any lawn treatment will work, you need a completely clean starting point. This means removing all visible waste — including old, partially decomposed deposits that may have been missed. A professional one-off deep clean can help if the buildup is significant.
2. Water the Affected Areas
Thorough watering helps dilute the excess nitrogen and salts in the soil. Give damaged patches a deep soak — at least 20 minutes with the sprinkler — to flush contaminants deeper into the ground.
3. Apply Lime (If Needed)
If your soil pH has dropped below 6.0, an application of garden lime can help restore it. Test your soil first (testing kits are available at Bunnings and Mitre 10) and follow the application rates on the bag.
4. Overseed Bare Patches
For areas where the grass has died completely, overseed with a suitable NZ lawn mix. Autumn (March–May) is the best time for overseeding in Auckland, as the soil is still warm but the weather is cooler and wetter.
5. Establish a Regular Cleanup Routine
Prevention is always better than cure. Whether you do it yourself or use a service like Backyard Buddies, weekly waste removal is the single most effective thing you can do to protect your lawn.
The Bottom Line
Dog poo is not fertiliser. It's a concentrated source of nitrogen, bacteria, and parasites that damages your lawn, contaminates your soil, and creates health risks for your family. The longer it sits, the worse the damage gets.
Regular removal — ideally weekly — prevents the vast majority of lawn damage and keeps your backyard safe for everyone. If you're tired of the battle, our weekly clean service takes the whole problem off your hands.