problems using black plastic under MM in sfg?

I attended a gardening class in which the teacher said that it was ok to use black plastic under the sfg box (which I did last year), fill in with the soil mix, and plant the seeds.  I bought a copy of the New SFG book and am wondering if I need to take the soil mix out and replace the plastic with landscape fabric.  I didn't notice a problem with drainage, but since the garden did poorly, maybe it was a problem????  Also I know that I only could find mushroom compost and cow manure as the "compost" mix and used Miracle Grow to supplement.  Still, the plants did not grow well.    Suggestions would be most appreciated.  Thanks!

Teacher,  Welcome to the Forum from California!  

If you can provide us with some more information, we will try to help you get a banner crop this year.   Was the teacher a SFG gardener?  When did you buy the book, last year or this year?  One of the wonderful things about SFG is that it works, but only if it is followed.  The closer to the SFG method one does, the better the crops.  Miracle Grow is nice for amending dirt, but it has wood chips in it that can tie up the nitrogen as they further compost (break down).  Therefore, it is not the best ingrediet for the Mel's Mix. What was the ratio of the cow manure, mushroom compost and Miracle Grow?  Did you also use 1/3 fluffed peat moss and 1/3 vermiculite to make Mel's Mix?  The black plastic may have created poor drainage at the bottom, making the last inch or 2 soggy and anaerobic.

Looking forward to some more information.  We are here to get it going in the right direction.

PS:  I used a bagged Kellogg product as the compost part my first year.   Things started off great and then stopped thriving.  The folks here got me straightened out and it has been great ever since.  One thing some folks do is make their own compost so they know they have a balanced compost from there on.

Hi Teachersld.  Welcome from Atlanta, GA.

I had the same problem w/ the compost when we set ours up last year.  With the same results.  (I also think I squeezed too many plants in too little a spot, but that's another issue.)

I do not have plastic under my beds.  But I do have a thick layers of newspaper AND cardboard boxes sandwiched between 2 layers of weed cloth.  As I'm cleaning my beds this spring, I'm putting down more newspaper in the box bottoms.  (Again, a thick layer.)

So - lessons learned:  Get my own compost pile started (Done - sorta...); Find some new types of compost to put in the MM; Don't squish everything together more than the book says.

I will not use plastic in my garden, if I can help it. Oxygen is a requirement for life in the garden , including the growing mix and I don't want to choke my garden. Also, I like that the earthworms can migrate into and out of the boxes as they need to.

AS to the mix, I'm afraid you have poor results due to poor soil health. IN other words, your plants probably starved.

Mushroom compost typically does not hold a lot of nutrition, but it can improve soil composition and tilth. Cow manure is good but isn't enough. YOu need at least 5 different sources of compost for good soil nutrition. Miracle grow is an emergency feed, but it wont last...

The trick is making a growing medium that is going to give good results for all the right reasons. This is mostly what you get with the Mel's mix. A healthy growing medium is what will give your plants good health.

Here is a good read: https://squarefoot.forumotion.com/t7452-mel-s-mix-how-strong-is-your-backbone <~~~click

camprn wrote:I will not use plastic in my garden, if I can help it. Oxygen is a requirement for life in the garden , including the growing mix and I don't want to choke my garden. Also, I like that the earthworms can migrate into and out of the boxes as they need.

Agree with that 100%.  IMO the soil needs to be ALIVE so that it supports worms and other microoranism and so many other creatures.  I feel that I am finally getting the hang of things as I mulched all my beds during this past winter for the first time, and now I have so many worms  that I never had before.

I will only use plastic if I want to kill something like quack  and Bermuda grass and similar stuff and after that that take off the plastic and put down compost etc so the the life in the soil can come back.

Teachersld from Kelejan in Canada.
Keep the questions coming.

I've had plastic under my MM for years with no problems. Be sure to poke drainage holes in it.

As others have said, your organic nutrients are lacking.

Thanks for all of the replies!  It was not a certified sfg instructor who taught the class.  I did use vermiculite , peat, and compost (only mushroom and cow manure) in thirds.  I only used Miracle Grow in a sprayer about every week or week and a half.  I bought the new book a few days ago and realize that I made a couple of major blunders.  One person who responded said that they had black plastic (with drainage holes) underneath.  Should I just poke holes in the plastic for drainage, add more compost (which I am still having trouble finding- so far I have found cow manure, forest compost, and Nature's Care Really Good Compost, but nothing else.)   OR  just remove the soil, replace the plastic with landscape fabric, and put the soil back in with added compost?? I will keep looking for other sources of compost in the meantime. 
I also have one more question..I am making another sfg.  I believe the new book recommends removing the grass before putting the landscape fabric down.  Is this necessary, or can I put down newspaper first, add a layer of landscape fabric, and then put the MM in??  Sorry for all of the questions, but I want to do it correctly this time

By the time I get around to finishing this reply, someone else may have replied.  Here's my 2 cents for the existing box.  You don't know what is going on down at the bottom.  There may be a depression in the ground where water is pooling.  If you just stick a knife in the mix and stab holes in the bottom, other plant roots may come up into the box for the nutrients and water.

Get a tarp, take all of the mix out and put it on the tarp.   Put 3 or 4 lengths of 2" x 4" on the existing plastic.  If you want to leave the plastic down, stab some holes in it for drainage.  Turn the box frame over and screw a 4' x 4' piece of 3/4" plywood to the bottom.  Drill 3/4" holes in the plywood for drainage.  Ex:  one in each corner of the box and one in the middle of each imaginary square.  Turn the box back over and set on the wood pieces.  If you don't want to use wood to elevate the box because of a lot of rain in your area, you can use a few bricks, cement bricks, etc.  Line the box with weed fabric and refill.  Add some of the new compost materials you will be buying to bring the level of mix back up to where it started out last year when you first filled it.  Now you have a box that drains well, is out of the reach of any invasive roots and is ready for grids and planting.

If you remove the grass for box #2, you may create a water puddle under the box.  Instead, cover the spot with plastic and stab some holes, and repeat what you just did with box #2.

I looked online for a Home Depot in Monroe (central north LA).  I also looked at Craig's List for Shreveport and Monroe but couldn't find much.  Here's what I found at Home Depot.

Home Depot, Monroe, LA:

1.  Nature's Way SFG Potting soil and Mix, (ready made Mel's Mix)  !!!

or

1.  Ecoscraps Compost (1st choice) or Garden soil (2nd choice), a well composted wood and veggies compost.
2.  Steer manure (manure)
3.  Natural Nitro 100% Worm Castings Soil Amendment (worm casting)    or
Noble worm castings (worm casting)
4.  1 cu. ft. Nature's Care Really Good Compost (yard waste)

Online:  Kelp4less.com  has kelp meal - you only use a little (spoon per square) so it goes a long way
eBay:  various worm casting sellers - use more than kelp meal (maybe a cup per square)

Try to find a 5th source.  Year-old pile of horse manure?

Thank you so much, Sanderson.  I think I have found turkey compost to add to the other ingredients that I have purchased so far and may have access to composted horse manure.  I may order some worm castings and kelp if I can't find those locally. Since I will be taking the existing soil out of the original box and adding landscape fabric , I will be checking underneath to see what it looks like there as far as drainage goes.  Thanks for the advice about the plywood bottom and blocks.  I may need to do that too.

check craig'slist for manure or compost, under the farm and garden banner . Also Yahoo freecycle.

I only checked craig's list for Monroe and xx (west of Monroe). A dearth of compost and worm castings.

I did find turkey compost, bone meal, and worm castings.  I am supposed to pick up vermiculite tomorrow from a farm supply store.  As far as the plywood is concerned, I will have to wait another week or so until I go to Monroe.  A worker from the local Lowe's told me today that their saw is broken and they don't have a way to cut it.  (I thought that it was a little humorous....hmmm...  building supply store can't cut wood l)
Also the other building supply store in town said that they can't cut wood either because of insurance issues. (I got some smaller pieces cut the other day for the frame of the box, but they had to use a handsaw.)  I don't have access to a truck, but can get 4x4 pieces in the back of my Camry trunk...just barely   
I have appreciated the simple instructions on the construction part of the sfg since my daughter and I are working on this. I hope that the instructions for building a vertical support and the cages are as easy

Hats off to you and your daughter doing the boxes.

Bone meal is not a compost. Think of it as a specific fertilizer of phosphorus. If multiple sources of compost are used, fertilizer should not be needed

I did a search for recycle centers in your stated location http://www.recyclingcenters.org/Louisiana/
Check, to see if they are making compost.
I started my first season with recycled compost, with a few additives I did very nicely growing plants