Hi,
Different types of soil react differently to the addition of OM. OM by its intrinsic nature will decompose and what Lyn
@Roseblush1 says holds true . In the long run ( not immediately) the soil tends to revert to its original natural ( geological) form. However, when looking at human artifacts, of which garden soil is just a sample, one should be careful of not confusing natural original soil properties from the one the gardener creates . The second type of soil is unnatural : is what is known as an agricultural soil. It requires some level of intervention such as tilling, fertilizing, ammending and so on. Depending on their initial composition, agricultural soils are a new type of soil and this may be more or less stable. My ancestors in the plains of the Ararat mountain in eastern Turkey, have been growing wheat on the same land for at least 4000 years. They have discovered how to keep that productive and in agricultural form which in many ways proves, what you say that the soil structure eventually changes into something different: yes it does, but necessarily everywhere. I haven't looked in detailed way what would happen with those soils if they are no longer kept agricultural. I would predict that they would revert to something nearer to the original. Lyn lives and gardens on a shallow forest soil; agronomically its not even considered adequate for agricultural purposes. In that sense one shouldn't forget that gardening although in such reduced scale is an agricultural branch of agronomy. Sometimes, home developers place houses where gardening is almost impossible to start with ( i.e Lyns case). And, the construction crew simply erased the shallow topsoil and left the almost bare rock. In those extreme adverse conditions Lyn was able to grow successfuly roses. She learnt how to create an artificial soil that does provide for their needs. Most people garden in less adverse conditions, however many are faced with other deterring conditions. One can be heavy clay to start with: what this thread is about , and the thread evolved towards the proof that initial adversity can be overcome... once one understands the need of a rose, and what type of given soil you are starting with . This ought not to be confused with what you should strive for. This new artifact called a garden bed, may need permanent addition of OM in form of leaves, compost, manure etc. Also other ammendments: it may require addition of rocks and sand ( or perlite, thank you
@margie) in the case of a very heavy clay substrate so that the resulting bed is a risen bed with a completely different drainage structure above the original soil level. As I understand this is what a perched bed is about. Yesterday I studied a bit about the origins of horticultural perlite. It is natural mineral that is baked in a kiln and thus expands into a very light material. In my part of the world perlite is very expensive (because it is very bulky and freight cost become astronomical), sand, also fine gravel is a much cheaper alternative. Both are mainly silicates and have the same composition as glass. I'm interested in keeping gardening cheap so that it becomes an option to the vast majorities. I also started to read about the other extreme: growing roses hydroponically. It is done nowadays in vats by commercial cut flower rose growers. In this other extreme everything is artificial and far from cheap. Would I ever grow roses hydroponically? No, I don't imagine my yard that way
. The only exception would be if my inquisitive mind would make me study root uptake properties of certain roses ( ie. new rootstock from wild species such as swamp rose). Hydroponics offers us the ideal lab conditions where variables can be tested. But this is clearly moving far away from what at least my idea of gardening is about...
