(08-08-2021, 07:18 PM)toomanytommytoes Wrote: Compost just isn't a very good growing medium for the longer term. In containers it seems to gradually lose its structure whatever you do. Perlite, bark, grit etc. all help aeration but eventually the organic matter in the rest of the mixture decomposes into dust. This leads to compaction and lower ability to hold water and air, which is bad news for roots. As has been said, in a container you don't have the insects or microbiome as you would in soil. Compost applied to the top of the container is just going to sit there and gradually break down with no structural effect on what's underneath.

(08-08-2021, 12:49 PM)Veggie Wrote:

(08-08-2021, 11:05 AM)Vinny Wrote: I've often wondered about Charles Dowding methods ongoing? If I cover with cardboard and then compost and plant through it what am I supposed to do when the crop is harvested and I am redy to plant the next crop in the same area? Do I cover with cardboard again and add compost or do I just add compost? Because I have a never ending supply of cardboard and to save on the cost of compost, is it not feasible to strip off a couple of inches of soil and add to wheelbarrow, after which it will be returned on top of the cardboard?

To hypothesise on your query Veggie I would say that in open soil worms would be an integral part of combining the layers of soil and stopping compaction. In a pot, you probably wouldn't have the worm population or any invertebrates to break down and mix the layers?

Would stripping off the top bit of soil count as "digging" because you're disturbing the soil?

(09-08-2021, 09:20 AM)Veggie Wrote: I'm no purist either, or a disciple of CD, so, if I had a ready supply of cardboard, I'd be doing the same.

(08-08-2021, 10:31 PM)Spec Wrote:

(08-08-2021, 07:18 PM)toomanytommytoes Wrote: Compost just isn't a very good growing medium for the longer term. In containers it seems to gradually lose its structure whatever you do. Perlite, bark, grit etc. all help aeration but eventually the organic matter in the rest of the mixture decomposes into dust. This leads to compaction and lower ability to hold water and air, which is bad news for roots. As has been said, in a container you don't have the insects or microbiome as you would in soil. Compost applied to the top of the container is just going to sit there and gradually break down with no structural effect on what's underneath.

Your post above ttt makes me wonder at what size of container does compost turn to soil, I have made my own soil by mixing vegative waste and course sand, made up in builders bag so about a meter cube I have had good crops from this for four years and it still looks very good, there have been other more prominent examples such as Inverewe Gardens and The Eden Project where soil was artificially made with outstanding results, but as you say, with smaller containers the contents deteriates

• 25 per cent sand waste from Cornish china clay mines
  
• 32.5 per cent composted tree bark
  
• 32.5 per cent composted green waste
  
• 10 per cent coal rich clay (lignite).
  

(08-08-2021, 07:18 PM)toomanytommytoes Wrote: Does the level in your builder's bag drop at all?

Here's what looks to be The Eden Project's artificial soil recipe:

• 25 per cent sand waste from Cornish china clay mines
  
• 32.5 per cent composted tree bark
  
• 32.5 per cent composted green waste
  
• 10 per cent coal rich clay (lignite).
  

Surprisingly high in organic matter, though composted tree bark is fairly resistant to degradation. I wonder if they have to top it up every year. Currently they're doing more research into artificial soil mixtures in conjunction with the University of Plymouth.