The Nitrogen in lawn fertiliser burns the leaves of lawns, turning the lawn yellow, brown or black. Nitrogen is the same nutrient that causes the spots created from dogs urine on lawns.
All lawn fertilisers must be watered in within a reasonable time period after fertiliser has been applied. The time frame for watering is usually dependant on the heat of the day. The hotter the day, the sooner fertilisers must be watered in to prevent fertiliser from burning the lawn. On cooler days, the time can be extended. However, it is never a good idea to leave fertilisers on the lawn for too long.
The maximum amount of time allowable is to always plan on watering fertilisers immediately or within hours of application in warmer weather, and within a day in cooler weather.
Unlike lawn fertilisers, wetting agents cannot burn lawns, because they contain no Nitrogen.
Highly respected Australian turf and plant breeder Todd Layt shares expert lawn care advice with homeowners on The Lawn Guide.