Until you get this figured out, I would not expand your planting operation. You can dump a lot of $ into a plot and not get anywhere.
Let me give you a for-instance: I've tried a bunch of things. I don't have a whole lot of money to throw at plots. I'm about 50/50 on my experiments. There is one mix that seems to be productive and work for me and that's ladino clover and wheat. The deer and turkey love it, so from now on, that's what I'm going to plant.
How I got there was a bit circuitous. Mind you, I was trying to do everything on a shoestring:
1) I found known patches of pasture that the deer and turkeys regularly fed. I went through and spot fertilized in the spots where I saw the most spoor. What I found was that the deer were eating mostly clover
2) I had a bulldozer in for a completely different job and I had him tear up a bit of pasture. I then went back and planted a few things to see what came up best. The pound of ladino clover took over everything else.
3) When I finally got around to putting in bigger plots, I used a ladino clover/wheat mix in one and I experimented with all sorts of stuff in the other. The deer loved the annuals in the other plot, but after the first cutting, they glommed onto the ladino clover, and never stopped. The other plot is due to be replanted this year.
4) In the next round of plots I experimented with the same way. I tried new stuff in one plot and stuck with the tried-and-true clover/wheat in the other.
My point is not to point you toward ladino clover, but to show you that this is a long process. Ladino probably won't work in sand/loam anyway. However, there will be something out there that will work somewhat the same way.
One thing that helped me a lot was the fact that I started out just strip disking a few places. In a few plots, the farmer didn't have a disc, so he chisel-plowed it. What that did was break up the ground and let the natural forbs compete against the fescue. For a few years, that was all I had. The deer hit those fields as hard as any, because they prefer weeds to grass. They also liked to bed in it.
Can you identify what seems to attract them? My investigation was pretty positive right off the bat. Where there was ladino clover, I had deer and turkey poop. By fertilizing with a little 12-12-12 around concentrations of deer poop I amplified the situation.
If you can start with a clover or some other nitrogen-fixing forb all the better. Once that gets a hold, it will fix nitrogen in the soil and it will cut back on your fertilizer needs in the future. What's nice is that while the deer and turkey are tearing up the ladino clover, they're pooping constantly. Over time, I'm getting all my fertilizer for free. My biggest clover plot is now looking better after 4 years than year 1, despite constant hammering from the deer and turkey.
Remember that mixing stuff is not necessarily the best way to go. I mixed red clover and ladino clover in one plot just to see what happened. The red clover crowded out the ladino, but the deer and turkey prefer the ladino. Now I have a beautiful plot of red clover that no one wants to eat, because there is so much ladino around elsewhere. When you try something, use discreet rows or sections.
Be careful which annual you pick to go with your perennial. I found that everybody loves black oil sunflower and sorghum. However, both have toxins that prohibit other plants from growing for up to 3 years after planting. I even found and article online where they were talking about using sunflower as an anti-weed border.
Ooops. I now have a nice strip of dead space in one field that nothing wants to grow in. The fescue is now starting to come up in there this year, so I'm going to have it rotovated and you can guess what I'm putting in.
Ask around. Somebody's going to know what works. They'll also know what doesn't. I had heard mustard was a good one for deer. While I was at the feed store, I mentioned putting in a test plot of mustard. One guy blanched. "You don't wanna do that!" he said. "I put in a little mustard in the garden and the darn stuff spread and now it's taken over a whole pasture. I can't get rid of it!"
Then again, be careful with the advice. One guy who cultivated a plot for me swore by yellow sweet clover. He said it was IT for food plots. It was a clover, but it also grew up to 3 feet high and made a nice habitat for bugs for the turkeys to eat. I took him up on the idea and special-ordered a bunch of it. Yep! It worked. Stuff came up all nice and lush. Deer ate it down to the ground and I never saw it again. It still sprouts in a few places, usually around the fenceline where the deer can't reach it. I later found out this stuff is now on some state invasive alien plant no-no list-- they make it sound like kudzu. Gee! I guess I could rent my deer out to take care of the problem.