Raised bed medium/design/mushroom composting tips

[taihaku]

We've just acquired a patch of land adjacent to our house (our land formed an elaborate curve around it). At the moment it is populated by a burned-out cottage (with associated soil pollutants) and a murderer's row of perennial weeds (including thick bramble, couch grass, bindweed and (oddly) japanese honeysuckle). The plan is to bulldoze off the house remains (nothing salvageable left there alas) and also a layer of topsoil to leave bare earth and then to set up a series of raised bed for our kitchen garden that will be nice and close to the house. My questions relate to raised bed design and content. 

I'm planning to "overbuild" these and make them really nice as I want the area to be a pleasure to be in/around. Basically we want to hit this out of the park as it will be our outside chill out/bbq zone as well as our kitchen area.

We're planning to build bed around a couple of feet tall. I am also planning to dig out the beds to a level of a foot or so below the surface so there's room for 3 foot or so of growing medium (the depth being perhaps some insurance against bindweed/couch grass penetration from beneath.

We're planning to use untreated half depth railway sleepers to build (allowing the edges of beds to become casual seating) and  I'm planning to put in place along the sides pipeholders to allow hoops of flexipipe to be set up to hold crop nets and so on. I'm also planning to lay soaker hoses up and down the beds for easy watering - does anyone else have any tips for "the ultimate" raised bed design? 

Also I'm pondering what to put in the beds. I have access to:
- huge quantities of mushroom compost
- straw
- woodchip
- unrotted manure
- chickens and their associated produce
- fresh seaweed in bulk
- municipal compost

I was planning to load the beds with alternate layers of wet cardboard, mushroom compost, woodchip, vegetable kitchen waste, worms, and seaweed and let it rot down (periodically turning and possibly using the chooks as labour for this) - realistically we're looking at putting these together this year for use next year due to time constraints so I have time to let stuff cook. Any suggestions/thoughts/pro-tips?

Also I'm looking at topping each bed with a straw/woodchip mulch early in the year and then spawning them with king stropharia and morel mushrooms (different varieties in different beds) - any tips on doing that in a working veg garden would be much appreciated.

[steev]

Bear in mind that if you use only organic matter the level will sink, requiring topping up annually (sounds like you have plenty with which to do that), which is problematic if you have things that are biennial/perennial; the "soil" will hold water very well; your veggies will grow like crazy.

I built my toddler daughter a "hill" of pure compost, sodded for a lawn; never needed to water more than once a week; always looked primo.

I think in some thread it was posted that mushroom compost is high in salt.

[taihaku]

Thanks Steve; as regards sinking my plan was to top up regularly with mulch (and hopefully thereby keep the mushroom patches going year to year). I must confess I hadn't thought about sinking perennials though - I do want rhubarb and asparagus in a couple of these so guess I'll have to ponder a solution involving some sort of inert bulking agent for those beds.

[mskrieger]

If you have access to fresh seaweed, surely you have access to sand? The asparagus will like that--it demands good drainage and doesn't mind a bit of salt.

[taihaku]

Mar 21, 2016 14:40:51 GMT -5 mskrieger said:

If you have access to fresh seaweed, surely you have access to sand? The asparagus will like that--it demands good drainage and doesn't mind a bit of salt.

seaweed is, I believe, subject to some sort of ancient customary collecting right. Removal of sand/rock from our beaches is not legal alas.

[steev]

Any sort of clean soil will serve. If you enjoy an ancient seaweed collecting right, I suspect the same goes for sand, provided it is done quietly in the dark of the moon.