When the ph gets below 5, the plots will not do very well and you will lose a lot of the attraction of a food plot. I've got a plot on my place that the ph got low enough that clover would germinate and then eventually die and the plots were so sparse that they wouldn't stand up to much browsing pressure. At 5.5 ph and up there is a tremendous difference in deer preference.
In my area, there are lots of deer and lots of food plots. I try to make mine the best in the area and that's where the deer want to be. Lime is one of most efficient amendments you can do and one of the cheapest. You don't have to get your ph to 7 but get it to 6+ and you'll see the difference and so will the deer
^^^He speaks the truth.