I like Mel’s first book/method better than his second version. The first version was to loosen 6 inches of soil and then mix 6 inches worth of compost into it to have enough for the 6 inch raised bed. You end up with 12 inches of well amended soil.
His second method was just 6 inches of compost on top of undisturbed soil. I can see that drying out quick.
The first method likely works better with heavy soil than with sandy soil for holding moisture but I think most of the US has heavy soil.
Agree. The vermiculite add-in to me is over-rated for moisture retention as well.
... heavy soil....
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I’ve gardened in heavy soil with a lot of clay. It can dry out and crack if aren’t careful.