Soil is the stuff I grow most of my plants in, the ones I don’t grow in pots.
It is derived from the local rock, soft slatey stuff, small bits of which are visible and sometimes abundant in the soil. Everybody describes it as “shilletty”.
If I analysed the distribution of article sizes I would obtain a description of my soils texture. In other words, a more scientific word than shilletty. I would imagine there to be a wide spread of particle sizes without any one of them dominating to make it “sandy” or “clay”. I doubt whether there is much of a clay fraction and there are none of the hard, round, even sized particles that define a sandy soil.
I garden this stuff, mostly by no-dig methods, spreading compost on the surface and growing my plants in it. When I was on my allotment a few days back, pulling up weeds, they came up very easily from the beds, the soil being loose and crumby. No, I haven’t left the L out of crumbly, though it was that too, what I mean is that the mineral and organic particles of the soil had become crumby, small lumps roughly wheat grain sized, with lots of air space between them. This is my soil’s structure.
The paths where I walk were quite different. Much harder to get the weeds out and with no structure discernible. I have to say it didn’t seem to be deterring the weeds much, but I wouldn’t want to try and grow lettuce in it. It is pretty easy to turn the crumby stuff of the beds into the compacted stuff of the paths, just walk up and down on it when it’s wet.
I know what I want, nice crumby stuff and I know how to get it, top dress with compost and stay off it. My plants grow well in it so they are getting all they need, anchorage, water, air and nutrients.
The soil ecology has turned my mineral matter and organic matter into a perfect growing medium, with very little effort on my part. Lucky me.
But. I worked on a nursery for many years before I retired and grew a very wide range of plants in pots, using peat for well over a decade before switching to peat-free for a similar period. The aim is to provide ideal conditions for plant growth, albeit in the artificial confines of a pot and with the environmental control afforded by a polytunnel. So I know that you can provide excellent conditions for plant roots to grow in with no soil ecology at all. For much of my career a chemical was added to kill vine weevil grubs and the added fertilizer would have seen off any myccorhizal fungi.
People grow plants by hydroponics, they build golf greens and football pitches from 100% dune sand (even particle size, no packing) and they garden in a myriad of different conditions across the globe. It may be soil science but it sure ain’t rocket science. The plants don’t need the soil bacteria or fungi or worms, they need the conditions that the bacteria, fungi and worms create.
Which is not to say there is no interaction between plants and soil life. The energy powering the whole system is coming from the sun, the plants capture it by photosynthesis and are basically the food source for the rest of the soil web. The soil organisms must exact some level of toll on the plants, but the plants will be happy to pay a small price for the good growing conditions they get in return.
Nor does it seem likely to me that nothing except dissolved plant nutrients in the soil water get taken up by the roots. I know that soil applied pesticides and herbicides pass into the plant. Of all the myriad organic chemicals that must be present in soils as organic matter is broken down, it seems likely that some will be taken up by plants. I am unaware of any consequences from this happening or from it not happening in sterile media.
I have never had my soil analysed, either in my garden or at my allotment. Someone else at the allotments did, there were all sorts of things above or below where they should have been. I never saw the report and neither did my onions, which seemed to do very well last year without knowing. I apply generous quantities of compost, which includes all our vegetable kitchen waste, a little fertiliser and occasional water. Perhaps it could be better still with the addition of something I am unaware is lacking but I shall probably never know.
It would be very hard to persuade me that adding anything other than the basic plant nutrients that I know are required in significant quantities would bring a cost effective benefit. I won’t be buying any rock dust, or compost enhancers, or myccorhizal fungi or beneficial bacteria. I have all of these things already, in my soil.
It’s worth bearing in mind that even humus, sacred cow of gardeners forever and then some, probably doesn’t exist. Glomalin may be a real thing, but isn’t beyond doubt yet it seems.
I was brought up as a digger. Digging creates a tilth, which works as a short term alternative to good structure, but in a few months collapses. It causes loss of organic matter by oxidation, damages soil structure, brings weed seeds to the surface and makes your back ache. It no longer makes much sense.
Having said which, when I first took on my plot, I trenched it end to end, turning the soil upside down. The surface weeds and seeds ended up 40cm or more down. By and large, that’s where they stayed. In the long run it saved me work. Would I do the same again? I think I probably would.