Nitrogen in the form of urea should work OK...however...if you just dump in a bag--it will plug up your filter and your pressure will be zero. You do have a filter, right? Stir with a canoe paddle to get it dissolved first.
Read through a bunch of old posts about spraying urea on Lawnsite. You have to keep the rate low to avoid burning the grass. Less than a half-pound of nitrogen per 1000 feet sq. High temperatures result in increased risk of burning the grass. Starts and stops and uneven spray will make it worse.
Practice on your own lawn for the first few weeks