There are a number of steps you can take to minimise the risk of harm to your pets associated with applying fertiliser .
Always read the product labels and follow all instructions listed. If you are unsure on anything, please check with your supplier before applying your fertiliser.
Granular and liquid fertilisers should always be stored out of reach of your pets. Granular fertiliser can easily be mistaken for pet food, and liquids can be mistaken for water. It’s recommended that you keep your pets indoors while you fertilise your lawn.
Granular fertiliser is safe to use as long as the granules are watered as instructed into the lawn. Once watered in, the granules are very difficult for your pets to access. But it is recommended to keep pets off your lawn for 24 hours after application.
Fertiliser and Chickens
The main issue with granular fertiliser concerns chickens. Chickens can source granules lower in the turf profile than other animals. it is a good idea not to spread granular fertiliser where chickens roam or make sure the granules have dissolved completely before letting your chickens return. This usually takes a few days.
Most fertilisers however are not that harmful to most pets; here is a good link you can check out http://www.pethealthnetwork.com/dog-health/dog-toxins-poisons/fertilizer-and-mulch-dangers-dogs
Once liquid fertilisers have dried on the lawn then you are fine to let your pets back onto your lawn. This can take a few hours depending on the weather.
If your pet is known to be a eat grass, it is best to keep them off your lawn for 48 hours, or as long as possible. Again, if you are using a liquid fertiliser and your pet does eat grass, please check with the manufacturer for what exact contents are in the product and make sure to request a safety datasheet for that product.
If you suspect your pets may have inhaled, ingested or come into contact with fertiliser (signs can include burnt paw pads, red and watering eyes, vomiting and lethargy) seek veterinary advice immediately.
Follow the above advice and you can provide a safe play area for your pets.