On a small garden, use a broadfork to break soil pan, lots of compost, not overwatering will be baseline
Discussion
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.