I have used milorganite at the first emerging signs of growth in the spring. It really worked well as I think the deer associated my garden with a bad smell!
However, as I move toward a more organic approach to gardening, I cannot recommend using this product, especially on food crops. Sewage has heavy metal residue that is not completely removable in the filtration process. Also, think of the times you have flushed expired prescription medicine down the toilet.
I was sad to stop this method of pest prevention, but I think my yard, my kids and my pets are better off.