Cover Crops: Sunflower & Compaction 

If you have high concentrations of heavy metals and your goal is to permanently remove them from your soil, I would dispose of the plants. Once they decompose anything that was taken up by the plants will still be in the material. Otherwise it's not an issue.

I leave the roots to decompose in the soil, if possible.

Leave the roots in. Reseed. Repeat. Ide imagine the soil slowly becomes more “grainy” making it less compact?

@@ThePresentMoment23 what if it's a black soil that retains moist or wetness brother?

@@simonpure109 the roots will help aerate the soil, I assume.

​@@simonpure109the roots help a soil become more water absorptive and free draining. The organic matter is a sponge that lets the excess it can't suck up pass through freely

Edit: …planting something…

Difficult to tell. I've seen cases where a hardened clay layer was impermeable to daikons. It's possible that just filling the useable soil horizon with living roots and nurturing the most vibrant soil ecology you can is the best medicine. Let the microbes and the worms soften that compaction layer over time and eventually roots will start punching through

I think that's a consequence of being at the end of the row and having full sun along the length of the stem, allowing the plant to build really large leaves. You might get a similar response with a low seeding rate using sunflowers as an emergent/tall layer in a multi-plant family mix.