You have to build trust with them, or they won’t care. They need to see your expertise, and understand why you make decisions. Communicate what you are doing and thinking. Tell them why you are doing and thinking these things. You always have to be straight with them. No prevaricating. No lies. No manipulation. You need to be a man of your word, and you need to shoot straight all the time. If you build trust this way, they’ll do anything for you.
The external stuff: bonuses and and perks—they might help, but they don’t really affect loyalty, which, to me, sounds like what you are looking for. A little empathy for their position also helps. You need to let them know that you know what they are going through. You’ve been there. Done that. And you use that knowledge to help them do their job better.
Also, you have to trust them. You can’t always be looking over their shoulders. Your job is to tell them what to do, and then let them go do it. They have to decide how to do it, too. Your job, as supervisor, is to let them know that if they run into any problems they can’t handle, you’ll be there to help. Your other responsibilities are to plan and coordinate, of course.
Finally, give praise honestly and often. Let them know when you think they’ve done well. Don’t snow them on this. It has to be honest, as everything else you say must be. Let them know that you will do your best to help them advance, because you think they deserve it.
BTW, how old are you? Have you had the opportunity to take any management classes?