As you can tell from the responses you're getting, not too many guys like you "growing your own deer". Mostly because they can't.
But to answer you're question, if you want to attract more deer and give them better nutrition both to improve the health of the deer and the amount of deer on a property then you need to plant a crop that they like. Deer absolutely cannot resist field peas. Sometimes in the winter you will see 100 deer or more in a field and wonder why they are there. Answer is likely field peas. By far the easiest and cheapest is alfalfa because it grows back every year and is quite a hardy plant. Next best thing is some mix of clover. I've also heard of turnips in many mild US states. Some of these crops might also be good at attracting and maintaining populations of upland game birds like ruffed or sharp tailed grouse.
My uncle used to have 40 acres of alfalfa and we had many sharp tailed grouse there every year, especially in fall. I remember seeing 20-30 birds every day. But when he planted timothy they all disappeared.
You will also need minerals. Salt is a mineral. I think the best to use would be Sifto water softening salt. You can use a large blue salt block commonly used by cattle ranchers but really the best is the small pellets.
There are a lot of guys on this site that do not want to interfere in the "natural course of things" as they see it. But they want to shoot animals from the natural world without spending any money or time to make them better.
I own two hunting properties totalling 550 acres and if it was easy to grow deer and other wildlife it would be called livestock. There are so many factors that will prevent you from getting to acheive your goal of increasing the quality and quantity of animals in your area. By far the most important are the fact that the government and many hunters themselves are opposed to making any improvements that might make a meaningful and positive impact on the health and numbers of deer and other wildlife. I mean afterall, why do you see so many cattle when you drive through the countryside? Wouldn't that be nice to see more deer, elk, and moose? At least I'd like to see more wildlife. And that's one of the reasons I bought my land. Yes it is a small amount but if no one cares to buy the land for the wildlife then soon there will only be hunters with nothing to shoot.
