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Soil Prep Questions: Amending "Select Fill" Dirt

1,723 Views | 3 Replies | Last: 1 yr ago by tgivaughn
dudeabides
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AG
We are completing the construction of our retirement home (greater DFW area), so we are starting to dream about landscaping. The house was built on a deep base of "Select Fill" dirt (which we believe to be a 60/40 mix of lean clay and sand). It's apparently great to build on, but it doesn't seem ideal for growing anything. It currently occupies most of the areas where we intend to install flower beds, so we're wondering what we need to do to amend this type of soil and/or if we need to replace it with regular topsoil so that our plantings will grow and thrive. If we do need to amend or replace, how deep do we need to go? In most areas around the house, there is about 4-6 feet of Select Fill before we would reach the native black land soil.

We will be planting mainly Texas native/adapted drought tolerant shrubbery like Texas Sage, Abelia, Agave, Dwarf Yaupon Holly, and perennial ornamental grasses…at least, that is the tentative plan.

We tried to pick the brain of horticulturalist/landscape designer about this issue and they recommended amending the soil with peat moss and organic matter as much as possible. No real specific advice beyond that. Some internet sites suggest that plants can grow in this dirt, but it gets so hard when it is dry, it is hard to believe anything can. However, it does seem to retain water to a certain extent under the surface. So, maybe there is hope.

One article I read suggested that clay-rich soils should be amended with expanded shale (3" add to the top then tilled-in to a depth of 6") and organic compost (incorporate " to 2" to a depth of 6") to support Texas native plants. That doesn't seem like that is very deep.

I had thoughts about sending a soil sample to the A&M Soil Testing Laboratory, but I doubt that will lead to any new revelations about the current situation.

What saith TexAgs? Any real-world experience out there?

txaggie_08
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AG
Pest mods and organic composts are pretty good advice. I would just throw that on and till it in before planting.
HDeathstar
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Either till in better dirt or dig out 6 inches and put down rose soil.

I like rose soil for beds, and lots of native mulch on top.

If I was building my beds again by myself, I would just build them up with native mulch, wait six months for the mulch to decompose some and start planting, then keep adding mulch every year. Mulch decomposes and is easier to move around then soil.
tgivaughn
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AG
Indeed you are getting the SOP answers that are very good but not specific enough formulas for either your bed "as is" nor ideal for such plants to thrive.

You'll want to supply photos with dimensions, depths with list of plants to an expert.

Dallas expert is Neil Sperry https://neilsperry.com/radio/texas-lawn-garden-hour/

Aggieland/Houston expert is Skip Ritchter https://kamu.tamu.edu/radio/radio-programs/garden-success/

both are free advice radio shows
you'll get more/better answers if you don't ramble on, listen for their questions, then answer prompt & short
TIP:

call them BOTH, as both have served in both locations and one might give better answers than the other on any given day, not to mention technical problems ala live radio
Ten words or less ... a goal unattainable
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