Oddbean new post about login | logout I like compost on the ground surface (+biochar for bonus points), covered with cardboard and then a few inches of mulch (woodchips are my favorite, but straw or hay also work). Basically old-fashioned lasagna gardening.
Really, anything to cover the soil is beneficial. I suspect that cardboard is less permeable than loose mulch and probably gives a slight improvement for water retention. That can probably cut both ways, since it will also slow/prevent infrequent rain from soaking in.
Sounds logical, plus i do think there's something about cardboard that stimulates insect and microbial activity. And in my area, we rarely have too much rain for extended periods, so the cardboard could help retain soil moisture. Just my initial thoughts.