Mel's Mix, TopSoil , Fabric & 1/3 Formula

Facts:

We are building 350 s.f  raised beds which are 2 ft in height. in a fully enclosed 20 x40' garden  
  *  We plan on filling the bottom 16" with topsoil from a local mulch yard.  (keeping reserve an extra 2" for mulch if needed)  
  *  6" of Mel's mix 
  *  2" allowance for mulch  

  *   I have the 3rd edition of S.F. Gardening which suggests: 
     *   adding compost back as each vegetable is harvested.   
     *   putting down landscaping fabric under the Mel's mix 

   * I have suggestions from S.F. gardening People saying I should separate the Mel's mix from the soil with fabric or cardboard.  Can't use cardboard as we are sensative to the chemicals that are or might be in the cardboard. 

   *  We have clay soil where beds are being built 

 

Questions:  
  *  How do we keep the 6" of Mel's Mix from mixing in with the topsoil underneath it or is that even a concern?      
  *  How do we keep the formula 1/3  1/3  1/3 intact  if just adding randomly new compost 
  *  If we put fabric under the Mel's Mix won't that inhibit the root growth of those veggies that want to grow below the 6" ? 
  *  and... if we do put fabric under the mel's mix to separate the MM from the soil, why not put something else less expensive into the bottom 16" 

Thanks in advance, 

Fishtell

Put the weed block fabric down first, then the 16 inches of soil, then the top layer of Mel's mix. Unless you like the idea of high raised beds, you don't even have to go with the soil- just go for beds that aren't raised up as high and fill with 5" or 6"of MM. The veggies don't seem to care- they don't lay down tap roots, with the exception of daikons and carrots, which will heave themselves up when they hit the fabric and keep on growing  If you really want high beds and run out of soil for the bottom, use the "lasagna method". Add a layer of uncomposted fresh garden scraps (even small wood chips, and even charcoal-not ash) to layer of soil until you reach the level you are aiming for. The scraps will break down slowly over time and add back some nutrients as they decay- so it's a win-win for the bed.

Thanks for the comment YardSlave, 

Any thoughts on the other parts of my questions regarding: 
   *   messing up the 1/3 formula  when adding compost  
   *   will the MM and topsoil blend together over time and mess up the formula? 


Fishtell

I hope I'm not misquoting her, but I think it was sanderson in another post who mentioned that you can use washed sand as a filler substrate for your raised bed. Whether sand is cheaper is than topsoil only you can determine. You could also designate squares of your bed where the MM goes all the way down (or at least 12 inches) for your root crops.

Fishtell wrote:Thanks for the comment YardSlave, 

Any thoughts on the other parts of my questions regarding: 
   *   messing up the 1/3 formula  when adding compost  
   *   will the MM and topsoil blend together over time and mess up the formula? 


Fishtell

In theory, you add compost to replace the compost used by the plants, so the mix stays the same.  I think that holds true for the first few years.  I have some 9 year old beds where the vermiculite and peat moss may have decomposed a bit,  but it's still a pretty good garden soil.

How do you know how much of the compost has been used up and how much to add?   I'm wondering if this 1/3  1/3   1/3 is just a very very rough guideline and maybe the ratio can be 50% compost .25% Vermiculite & 25% Pete Moss?   Its appears to be pretty difficult to figure out how much of your compost is missing from the formula.

New to the forum and after tiring of the pandemic last year like many renewed my garden or tried to.  Ended up building several 4'x8' raised beds 32 inches high with a 6 inch ledge all around for support. Beds are 39"-44" apart for room to manuever

 Getting older and bending all the time isn't all that easy and likely to become less easy.

Ran across hugelkultur and thought it made sense especially given the large woods around us and lots of available leaf mulch and decomposing wood logs. (oak, maple and ash).

So with that I've put the logs, and leaf mulch interspersed with green materials.  Plan to add 12' Mel's mix on top.  I've not completed that last part.  
I understand 12" may be overkill but do plan many root vegetables, carrots, beets, etc.

And I thought why not?

Any helpful suggestions are certainly welcome.  

One question I do have is that the suggested density on the Sq Ft gardening book seems very tight. Should I just follow the suggested planting or have others found that certain plants are challenged with the density?

Be well

Richard

RichardMack wrote:
One question I do have is that the suggested density on the Sq Ft gardening book seems very tight. Should I just follow the suggested planting or have others found that certain plants are challenged with the density?

Which plants are you thinking of?

Trying to grow Unzen Flat White onions, Wala wala onions and some interesting other plants like costulota genovese tomatoes, rainbow swiss chard. wondering if swiss chard is to big?
in general really new to Sq Ft
Thanks for the reply

FishTell,
Hello from the other side of the state.

OhioGardener nailed it...the compost gets used up and needs to be replenished. The peat moss and vermiculite are used to help with moisture retention and also keep the Mel's Mix (MM) loose and friable. 

6" is all you need for most veggies and flowers. For tall carrots, you can build a small "extension" box filled with MM. With that said, I have had good results with smaller carrots in the 6" beds. 

As for not bending over, I suggest you search Table Top or Tabletop on the forum. you will see several options for building them with different bottoms.

RichardMack wrote:Trying to grow Unzen Flat White onions, Wala wala onions and some interesting other plants like costulota genovese tomatoes, rainbow swiss chard. wondering if swiss chard is to big?
in general really new to Sq Ft
Thanks for the reply

Hi Richard, Welcome to the Forum from California!

The spacing with SFG and Mel's Mix, really does work. In general, 9 onions can be planted per sq. ft. The Wala Wala are big so you may want to go 4/sq or alternate square is 5 and then 4 onion. I grow Swiss chard at 2 per square and harvest outside stalks and let it continue growing. Rainbow is a neat variety. The Costulota genovese tomato is an indeterminate variety which means it will continue to grow tall. You will have to figure out how you are going to support it as it grows tall. The EMT and nylon trellis netting shown in the book is an easy way to build one. Most use zip ties to secure the netting. Normally, one indeterminate per sq ft is used, but that requires pruning to maintain one stem. So for a beginner, I would suggest allowing 2 squares along the trellis. Happy gardening.

Fishtell wrote:How do you know how much of the compost has been used up and how much to add?   I'm wondering if this 1/3  1/3   1/3 is just a very very rough guideline and maybe the ratio can be 50% compost .25% Vermiculite & 25% Pete Moss?   Its appears to be pretty difficult to figure out how much of your compost is missing from the formula.

I think your questions have been answered, but I will summarize. Start with the 1/3, 1/3 and 1/3 ratio for the Mel's Mix. Add enough blended compost to restore the original height of the MM. Sometimes it's just a trowel full, other times it may be a bucket or more. What ever it takes.