Is it safe to use fertilizer on ones grass if you have geese and ducks? This will be our first year with waterfowl grazing in the yard, and I just don't know if I should put any fertilizer down this spring. I am thinking that I probably won't need to fertilize the grass with the ducks and geese on the lawn. They will be fertilizing it on their own, if you know what I mean. Is fertilizer toxic to waterfowl?