This is probably my biggest problem. How do I solve this?
Discussion
Small plot or broad acre?
Small plot, coastal central California. There's a 4ft by 20ft stretch we've kept having issues with plants dying. Original there was jade plants but they all started rotting & dying after having been there many years. We replaced the soil with store bought & tried growing lavender which took well and flourished for about 2 years. Some of it is still there but a significant chunk of the center stretch is dead. We have some green type of aeonium that's been flourishing. We use it on the border line of the patch.
Dig up a hand full going at least 6-8 inches down and smell it. Does it smell earthy (forest after a rain) or sour (on the more putrid side)? I'm betting on the latter. Also, is it the last place to dry up after a rain?
I'll bet you planting that radish and a mix of oats and annual rye grass on it for a couple of seasons will kick start it.
I found this for you: https://www.nrcs.usda.gov/plantmaterials/capmctn13333.pdf
What USDA zone?
One way I dealt with in in a backyard setting was to plant tillage radish (AKA oil seed radish) in USDA zone 6.
It's a biennial that you plant in late summer. It will freeze kill or, if it survives the winter will summer kill. It breaks apart compacted soil and leaves a bunch of mass in the ground that attracts and feeds earthworms. The seed is rather cheap so you can do this over a handful of seasons without breaking the bank.
On a small garden, use a broadfork to break soil pan, lots of compost, not overwatering will be baseline
Not over watering is easy for our region. I used a tiller to break up a good amount of soil after the first patch of dead plants. I replaced the soil with many bags of soil bought at my local hardware store. Worked great for about 2 years and now we're getting more death. Not the whole patch though, just the center.
White clover works nicely.