Soil Structure

[Smallaxe]

It is said that Organic practices promote good soil structure because it is built by microbes.
Heavier soils need structure. Heavier soil is what I am addressing here.

Does adding compost to the surface add structure 2-3 inches down in a heavy soil?
How about grain meals?
Does too much water and aeration/tilling destroy structure?
Would good soil structure allow nutrients to go deeper into the soil and find CE sites deeper in the rootzone, with routine applications?

[Itsthesoil]

When establishing new lawns, the more practical solution is to fracture the clay subsoil and add organics. Then add topsoil 4-6 inches with organics mixed in, maybe 2-3 cu yards per 1000 SF according to University white papers. As far as existing, deep tine aeration and filling the hole with sand as well as organic top dressing may be the best method. All that is out the window if there is heavy, constant traffic. Compaction is the biggest issue. Studies have shown that no matter what you do, if a soil is compacted, grass will be way less healthy.

[ICT Bill]

You can use italian rye grass to fracture the clay soil, their roots will go down 2 to 3 feet. It is an annual so when it dies off in the heat of summer it leaves all the roots behind, these are pathways for other roots later and food for the good guys

[Prolawnservice]

It is said that Organic practices promote good soil structure because it is built by microbes.
Heavier soils need structure. Heavier soil is what I am addressing.
I'll give it a stab.
Does adding compost to the surface add structure 2-3 inches down in a heavy soil?
Yes, eventually.
How about grain meals?
Yes, even slower.
Does too much water and aeration/tilling destroy structure?
It can, especially if the soil is saturated and worked while wet, it collapses the air space. Good soil needs aggregates, not fluffiness. Damage would come more from tilling than aeration(depending on the aerator).
Would good soil structure allow nutrients to go deeper into the soil and find CE sites deeper in the rootzone, with routine applications?
I would think yes, On the other hand, the nutrients that are mobile are so, because they are in a solution, and I think the solution would take the course of least resistance, so I guess it would depend. Not that routine applications have as much to do with it as soil structure.

[Smallaxe]

I thot so too, that providing a good physical structure that promotes drainage would be helpful. Compostted sand is a good friend in the clay soils.

Italian ryegrass!?!? How does that stuff look when mixied in the lawn as an overseed?

"... Good soil needs aggregates, not fluffiness. Damage would come more from tilling than aeration(depending on the aerator)..."

That was part of my question. The aggregates are formed by the microbes, from what I understand. The soil 'should have' a good physical structure to begin with, but the 'real work' in soil structure is done by microbes. Is that true?

If this chain of thot is correct.
Ideally - we would want water soluable nutrients filtering through the aggregates dropping off the elements onto properly prepared CE sites, deep within the rhizosphere.

Getting back to the compost part of the question:
What is actually happening when the compost interacts with the soil to make the soil aggregates? - and - how does it work deeper into the root zone?

Perhaps another Analogy... :)
thanks

[Kiril]

http://soils.usda.gov/sqi/publications/files/sq_eig_1.pdf

[Smallaxe]

Thanks, Kiril,

This discussed the formation and durability of soil structure and the basic ingredients that helped or hindered the possibilities. Cool.

Not all clays are equal, but sand don't make aggregates at all. :)

Soils with over about five percent iron oxides, expressed
as elemental iron, tend to have greater aggregate stability.
Soils that have a high content of organic matter have
greater aggregate stability. Additions of organic matter
increase aggregate stability, primarily after decomposition
begins and microorganisms have produced chemical
breakdown products or mycelia have formed.
Soil microorganisms produce many different kinds of
organic compounds, some of which help to hold the
aggregates together. The type and species of microorganisms
are important. Fungal mycelial growth binds
soil particles together more effectively than smaller
organisms, such as bacteria.
Aggregate stability declines rapidly in soil planted to a
clean-tilled crop. It increases while the soil is in sod and
crops, such as alfalfa.