Specialty Gardening: Suggestions for amending container potting mix/soil?, 1 by tapla

tapla wrote:
Cypress mulch is mildly allelopathic, and the effects are magnified somewhat when the mulch is incorporated because of the accelerated rate of breakdown. Sometimes, when you buy "compost" in a bag, you get a lot of things that aren't ideal for the soil. The same is true about topsoil. There is little (no?) regulation re. what can be put in bags and labeled as either topsoil or compost. There could be an issue involving what was in those bags - a soil test might ferret that out.

You CAN incorporate pine bark into the soil if you wish, and it WILL help to create channels in the soil for air and water, but it's greatest contribution will be as a result of what it offers as it slowly breaks down. You WILL experience some N immobilization if you do, but it won't be as bad as most other forms of organic matter (other than finished compost) because it breaks down so slowly. I'll try to remember to leave a picture of the soil in my raised beds before I leave. It's made of pine bark, sphagnum peat, Turface, and sand. It's a wonderfully rich soil with great tilth (you can actually SEE that when you look at the picture.

Remember, whatever you do, you need to look FIRST to correcting whatever is keeping microorganism populations subdued. They are your gardening partners, and if they are not capable of flourishing, no amount of organic matter will be of significant help.

In contrast top what you'll see, I have 2 - 4x8 beds that I originally filled with bagged topsoil and other things like bagged manure and compost - more than 15 years ago. The beds have never even compared to the others with the soil I described above, even though I amend then regularly with organic matter and mulch them with pine bark. I can't honestly make the connection to the original ingredients though, because the beds are near some black walnut trees and I fear their allelopathic effects may well be coming into play, but it is a possibility.

Back to the pine fines: If you do use them, you'll simply need to watch closely for signs of N deficiency. If you recognize that occurring, be at the ready with a high-N nutrient source to compensate. I found that after the first year, additional N applications were unnecessary.

Al