My experience using what I call "Purple Top" turnips down here in the deep south is good ... plant around late September to early October time frame. Cost about $.30/oz. last. I use them as a minority "mix" with other cool weather food plot seeds that I plant ... forage oats, buck wheat, Elbon rye, Austrian winter peas and Crimson clover. As stated in the exhaustive information, pH around 6.5 is great. Best in loamy soil. Deer seem to hit the leaves sporadically. Once the roots mature and sweeten up with first frosts, the deer will often wipe out the entire crop in a few weeks.
I intentionally plant a few of our better suited plots with a rather heavy mix, and keep them thinned. That way if the deer are not hitting the food plots in daylight, once the turnips get going good, at least I'll may have something for supper ... turnip greens and roots cooked down with fat back & plenty of pot liqueur ... over corn bread !!