Author Topic: Topsoil recommendations inside greenhouse?  (Read 695 times)

matt_citrus

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Topsoil recommendations inside greenhouse?
« on: September 10, 2023, 03:49:50 PM »
I'm in the last stages of greenhouse construction, and my base soil is a fine, but light, clay/silt. Are there any recommendations for topsoil ("normal"? amended with mushroom compost? other?), and if there are citrus-specific adjustments (for example, make more acidic) to mix in to any standard topsoil.

brian

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Re: Topsoil recommendations inside greenhouse?
« Reply #1 on: September 10, 2023, 03:54:55 PM »
My native soil seems to be just fine for citrus, it is clay to clay-loam

fruitnut1944

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Re: Topsoil recommendations inside greenhouse?
« Reply #2 on: September 10, 2023, 05:08:01 PM »
Almost anything but a sticky clay will work. The best would be some kind of loam. Sandy loam, loam, or clay loam will work as long as it drains well.

If your base soil is a silty clay you could just add some sand and till it in.

You should have a soil test run on what's there now. If possible, get a recommendation from the soil lab for the crops you want to grow. If it needs lime apply that and till it in before adding the top soil.

brian

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Re: Topsoil recommendations inside greenhouse?
« Reply #3 on: September 10, 2023, 08:43:16 PM »
I have found that drainage isn't too much of a concern in a greenhouse where you can control the watering.  If the soil in your greenhouse is at or above the outdoor soil level, and the outdoor area around it is not itself swampy, I think you will be okay with even heavy clay. 

I do have a low portion of my greenhouse that is actually below grade because the greenhouse is built into a hill.  During heavy rains I found water would flow under the foundation stemwall and up into the below grade portion of the greenhouse, flooding it somewhat.  I solved this by putting in a french drain and sump pump on that side. 


drymifolia

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Re: Topsoil recommendations inside greenhouse?
« Reply #4 on: September 12, 2023, 01:14:17 PM »
If you haven't yet, send in the soil for a soil report. The local extension here does them for free. That'll give you a better idea of whether you should be adding anything like lime or organic matter. My pH is a little low for citrus, but avocados love it. The citrus that got lime added to the backfill is much happier looking than the one that didn't.

My subsoil is a fairly compact silt/clay/sand, and other than lime, I've only really added aged compost as a top dressing/mulch, and that has worked well. No other topsoil additions.

matt_citrus

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Re: Topsoil recommendations inside greenhouse?
« Reply #5 on: September 20, 2023, 02:40:17 PM »
Soil test results:
P 7 lb/A
K 102 lb/A
Ca 716 lb/A
Mg 122 lb/A

Zn 0.4 ppm
Mn 15.9 ppm
Cu 0.4 ppm
Fe 12.3 ppm
B 0.1 ppm

Soluble salts 243 ppm

pH 5.2
Buffer index 6.1
CEC 4.0 meq/100g
Acidity 38.9%
Base Sat. 61.1%
Ca Sat. 45.1%
Mg Sat. 12.7%
K Sat 3.3%

Organic matter 1.2%

drymifolia

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Re: Topsoil recommendations inside greenhouse?
« Reply #6 on: September 20, 2023, 05:43:23 PM »
5.2 pH seems low, no? That's lower than mine, and my citrus definitely prefer when I add lime to their backfill.

fruitnut1944

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Re: Topsoil recommendations inside greenhouse?
« Reply #7 on: September 21, 2023, 03:04:39 PM »
My soil test results come back as ppm. So it's hard to compare but I think your P and K are low. If you lime to ph 6.5 that will add enough Ca and Mg.

The secondary and trace elements are better left alone unless you get a deficiency which is unlikely. It's too easy to get into a toxic range if you start adding those.

matt_citrus

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Re: Topsoil recommendations inside greenhouse?
« Reply #8 on: October 02, 2023, 08:15:29 PM »
In conclusion...

I raked 15 lbs of dolomitic lime over 700 sq ft to slightly raise pH.
Then spread 6 cu yd of topsoil / compost mix on top, raking in 25 lb of organic bone meal and 25 lb of organic 3-4-4 slow release. Soon spreading 5 cu yd of pine bark to allow the soil to digest slowly.
Trees are in rootmaker pots and will sit on top.

Millet

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Re: Topsoil recommendations inside greenhouse?
« Reply #9 on: October 03, 2023, 05:26:20 PM »
NPK & Mg inside a greenhouse are mostly controlled  by the fertilizer program that is used.

Seanny

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Re: Topsoil recommendations inside greenhouse?
« Reply #10 on: October 04, 2023, 10:34:30 AM »
Pine barks break down fast inside an orchid pot, but take years for mulch application.
I would switch to wood chips.

1rainman

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Re: Topsoil recommendations inside greenhouse?
« Reply #11 on: October 04, 2023, 11:32:03 AM »
Citrus doesn’t like to be mulched