tapla wrote: Good question and a good opportunity for me to go a little deeper into why your choice of soils, and particularly their structure is so important to the o/a health of the planting.
I think the most important part of the message carried in this thread is that if you provide a soil that starts out as a well-aerated medium and stays that way for the life of the planting or at least the interval between repots (as opposed to just potting up), you'll have done yourself a considerable favor that will be manifest in your ability to consistently produce healthy greenery. There is a stark difference between growing in the garden and growing in containers. On a scale of 1-10, with 1 being growing in the garden and 10 being full scale hydroponic growing, container culture is probably about a 7 or 8. IOW, container culture is MUCH closer to hydroponics than it is to growing in the earth, so it shouldn't be a surprise that much of what works well and holds true in the garden, DOESN'T work well and can even be counter-productive in containers.
I think there are actually two points in your question that need to be addressed. One is, 'what do these organic soil amendments do to the soil's structure, something I think should be judiciously watched over'? The other is, 'what do/can they provide and how effective are they/can they be'?
From the structural perspective, growing in soils comprised of fine particles (peat, compost, coir, sand, topsoil ....) already presents a significant set of problems described at length above, so for best results, we would want to shy away from those soils whenever possible. Adding even more fine ingredients to your soils, like worm castings; manure, which breaks down quickly; vermipost; various meals designed to to deliver nutrients - hoof/feather/bone/horn/cottonseed/alfalfa meals .....; all add to the problem of increasing water retention and decreasing aeration in a soil that is probably already too water retentive from the outset.
From the nutritional perspective, there just is no way to make nutrients available to plants in anything resembling a favorable ratio and on schedule (so WE know what is actually available, and when) than via soluble synthetic fertilizers. It is immeasurably easier and more effective.
Before I explain, I'm going to say that I am results driven. I don't care about ideological or political arguments against soluble fertilizers. If a person wants to self-limit by allowing politics or personal ideology to take precedence over what is most efficient and best for the plant, I won't argue the point, but I will debate the issue from the perspective of what works best and most efficiently.
Using organic soil amendments in containers is fraught with uncertainty. Plants cannot absorb nutrients locked in large molecules that make up the even larger hydrocarbon chains that must first be cleaved by soil biota (soil life) before the nutrients can be reduced to an elemental form plants can take up. The problem with this scenario is that soil biota populations and activity levels fluctuate dramatically in containers. Since we depend on their numbers AND activity, their ability to make nutrients from organic sources available is very erratic. What you apply today in the form of organic soil amendments may not be available for weeks. The term 'organic soil amendments' also includes fertilizers that derive nutrients from organic sources, as that term more accurately describes them.
In comparison, when you apply a soluble synthetic fertilizer, like Foliage-Pro 9-3-6, you can be sure you're supplying nutrients that are immediately available for uptake, in the same ratio in which plants use them, and you know exactly how much is available. It doesn't get any easier. I noted there is a technical difference between a fertilizer (Miracle-Gro) and a soil amendment (feather meal), but even that point eventually becomes moot from a strictly nutritional perspective. Plants take up elements that are dissolved in the soil solution and in ionic form. What they take up are salts. As noted, the large molecules that make up hydrocarbon chains in organic fertilizers/soil amendments cannot be taken up by the plant unless the hydrocarbon chains are broken down into elemental, soluble form by soil organisms. At that point, the elements from soluble fertilizers are exactly the same as the elements from organic sources, which is why the plant could care less. At the point in time where nutrients are assimilated by plants, they are ALL soluble and in elemental form, regardless of whether they came from a dead fish, compost or a hose-end sprayer.
I'm all for easy and uncomplicated. Nutritionally, you can hardly go wrong using a 3:1:2 ratio fertilizer like MG 24-8-16 or 12-4-8, or my favorite, Foliage-Pro 9-3-6.
Thanks again to all for the kind words. The little Portulacaria afra (mini jade) is a cutting from its dad in the picture above. I saw a plant in a thimble once, which gave me the acorn idea. To grow it, I drilled a hole in the bottom of the acorn after filing the bottom flat so it would be stable. It sets in a jar top on a paper towel under lights. I water it every night with distilled water from an eye dropper, and fertilize occasionally. The acorn lasts about a year before it rots & the roots break it up.