Go buy some fertilizer for your lawn. Don't worry about what kind because you don't give a crap anyway and it would be better if you bought the wrong kind. Put the spreader on a high number so it comes out nice and heavy. Make sure that when you fertilize the fertilizer goes in his lawn too. When your lawn starts to burn up and turn yellow in a couple of days be sure to practice the "man, I must have over fertilized" look. Use this look when he comes over bitching that your lawn is yellow. Tell him that you tried to do what he wanted. He won't bug you again.