What ever made you think there was a minimum acreage for QDM involvement?
A landowner/steward can improve habitat, harvest more does, exercise some restraint on bucks and educate him/herself on 5 acres! That is QDM my friends.
I wish I had 200 acres to hunt and cultivate!
The general rule of thumb I've seen is 300 acres as a minimum for doing QDM. The reason is that unless you have a piece of ground of reasonable size, there will be too much going on outside the boundaries of the managed area to effectively manage it. Chief among these is immature buck harvest by the neighbors.
If you sit on a plot of less than 300 acres, one of your first priorities should be enlisting the cooperation of the neighbors. Larger than 300 acres, you can begin setting your own agenda.
I hunted 40-80 acre parcels most of my career. I have hunted 5 and 20 acre parcels as well. In each of those instances, there were not enough deer resident on the property to ensure that anyone could control the quality of the bucks. If you passed on an immature buck the guy next door was probably going to harvest it.
I am actively managing a lot of things. Chief among these is access to the property. I have also done a lot of habitat improvement. I have a deer sanctuary that draws deer from all the neighbors. When the shooting starts, they all run over to my place. However, I know I can't personally control the antler growth on animals that may roam over 10-15 square miles during the breeding season. All I can do is make my little 200 acre plot as inviting as possible and keep my does happy.
Antler growth has improved on my acreage over the past 8 seasons. However, I attribute that to several neighbor working independently to limit access to their properties. When I moved in, my place was a free-for-all, and so was most of the adjoining properties. About the same time I cracked down, new neighbors moved and they cracked down too. There are a lot fewer hunters in my part of the county now and it shows. However, if things had stayed as they were and I was the only fellow doing my QDM thing, all I would have done would have been to let bucks pass for others to kill.
Starting out, I had no illusions of being able to do QDM. My first couple of bucks taken on the property are evidence of that. However, within 3 seasons, good deer started to show themselves under our stands. It's funny, but our little bit of heaven still has the reputation of having no good bucks. Everyone says our ridge is "Full of does, and spikes, and not much more." Shhhhh. Don't tell anyone.
Now, is that QDM? I dunno. To me it's just a city guy wanting a place for him and his kids to hunt.