If you have existing patches of sand burs, apply corn gluten in meal or granular form starting around Feb. 15th. When the weather gets hot and over 80 degrees in the daytime, spray as much of the area as possible with vinegar, d-limonene & soap mixture to burn it up. I've seen this work in full sun on an 85 degree day to reduce these plants to dry brown sprigs in a 4 hour period. If you have too much area to spray, mow them down to the ground. They don't like that.
I rid several areas of land of grass burs by mowing them down to the roots and applying the two basic first steps in restoring soil health: 1)molasses and 2)humate or compost. Sand burs are typical of soil that is low in humic acid. If you raise the humic acid level, you destroy the ability of the sand burs to populate the area. So, how do you raise the humic acid level?
You increase microbe activity so it can break down organic matter. Humate is faster than compost but both will work. Put the molasses down in either dry or liquid form, but use it! And do not be stingy...use it well and heavily. You will only do good. To speed up the rejuvenation, do it as regularly as the budget will allow. Once a month will do for starters, and I'm betting after two applications you will see a LOT of improvement.
Just a word of warning: Don't scrape the soil because you will be taking yourself back to square one with bare ground and nature trying desperately to cover it. You will just create problems for yourself.
We always called 'em "stickers" because they stuck to my socks and stuck me in my soft, tender feet! Ouch!