thats one good natural and free fertilizer. another is pee. you can drink about 2L of water over about 10 minutes. your first load of pee will be yellow, too strong for the plant. the next piss should be almost clear, thats the stuff! good source of nitrates for veg. then u just piss at the base of ur plants. its easy, free, and you don't gotta handle anythin dirty (like shit)