A 70/30 compost to soil mix will shrink as the compost is digested requiring that more compost be added so there is no need to dig out those new beds but a soil test of those beds would be in order to see if the pH and/or soil nutrients might be a problem. All vermiculite will do is improve water flow, drainage, and may not be necesary.

My raised beds were bitten by a too-high percentage of organic matter. Interestingly, they did great the first year, and so last year I raised them again (I'm using those wall stones with a little lip on the back), and put in a similar mix. However, this time they shrunk like mad. I've been wondering what caused that, and my guesses range around ideas such as "different weather last year" and "maybe the soil microorganisms have really established themselves now."

This year I'm lining myself up for needing to dig out *everything* (it's a perennial herb bed) and re-plant...at which point I may raise the bed by yet another stone-height. I guess I'll be purchasing a bunch of topsoil this year.

For those wondering, I'm not really a raised-bed fan, but it's the right answer, from a decorative standpoint, for this particular space.

Howdy Folks,
Both of your beds are doing what would be expected of them.
I would say you have both done well.
From this point on...forever... ;-)
you will need to continue to add Compost to top off your beds each year, your beds are a living organism,and if they ARE NOT SHRINKING, then I would be concerned.... they would be stagnant and not produce as well as could be expected,than if they were teeming with Microbial life.

DO NOT Dig out anything just keep topping them off with Homemade Compost or the best Compost that you can get your hands on...

Personally Leira I would not add rocks, but they won't hurt anything, but they won't help anything either, if you can,fill those beds with something the bed boarders want to eat and consume.

{{gwi:71559}}

I have had significant shrinkage in the original beds, and have added additional compost etc. as needed.

The new beds with the subpar compost were overfilled, with the compost initially being mounded up several inches over the boards. I have been redistributing some of it, and when I can get room enough I will add other compost.

I am planning to purchase some earthworms for these beds also.