Caliche

[Marjolein]

Hi, I am going to plant a palm and there is a lot of caliche rock. How deep should I dig for the roots to be able to grow? The Palm is a 

Pritchardia Pacifica.

[sonoranfans]

From the University of Arizona Agricultural college

Caliche Management.pdf

You may need to test your soil to see if its calcerous caliche.  IF the pH is too high phosphorus wont be available to the plant.  I grew palms in caliche soil in arizona that had modest calcium.  I would read the document carefully as it could be tricky to keep it happy depending on your soil/ammendments.  I will say one thing, tis very bad to dig a hole and ammend just inside the hjole, you have to blend the soil so roots will grow into the surrounding soil.  IF the ammendment transition is not gradual, the plant will grow like its in a pot, rootbound and all.  The roots will turn inward and never develop properly. 

[Silas_Sancona]

Is the " challenging " rock / soil layer Caliche or a thicker deposit of Marine - derived Limestone type rock?  

While very basic on details, this Wiki article regarding Aruba's Geology has a decent map of the rock formations/ types that occur on the island..  There are other geology -related websites that will offer more detailed info / maps.

Article:  https://en.wikipedia.org/wiki/Geology_of_Aruba



Map from the above -related article ..Hopefully in better detail:



As a general rule, anything referred to as Limestone / Coral or Calcareous -derived on the map will be highly alkaline.  ...Are rock types of Marine origin.

Rock types like Basalt, Granite, Quartz or Tonalite will be Acidic, and Volcanic in origin..

Conglomerate - type rock deposits = can contain both alkaline and acidic rock types..

Depending on your specific location there, you may be sitting atop one of the islands Limestone / calcium -rich rock deposits..

In that case, palms that prefer soil types that are more acidic may be more of a challenge to grow well / require consistent soil amending  to counteract the natural tendency toward alkalinity / effects of it on the plants.. esp if the deposit of Alkaline -based rock is quite extensive and /or deep.

 

[Marjolein]

I read the pdf already however it does not state how deep the hole should be for a palm,  water is draining now, we dug a large hole, it is very wide. In this particular place I had planted madame jananette, they were giving a lot of them and then suddenly stopped growing. I think the water could not go down and the roots rotted. 
I had 3 mango trees planted in another place in the yard, suddenly they turned brown, after 3 years and died, one of them was over 2 meters high. 
I have a washingtonia which is doing fine.

 

[Silas_Sancona]

30 minutes ago, Marjolein said:

I read the pdf already however it does not state how deep the hole should be for a palm,  water is draining now, we dug a large hole, it is very wide. In this particular place I had planted madame jananette, they were giving a lot of them and then suddenly stopped growing. I think the water could not go down and the roots rotted. 
I had 3 mango trees planted in another place in the yard, suddenly they turned brown, after 3 years and died, one of them was over 2 meters high. 
I have a washingtonia which is doing fine.

 

Curious, when you fill the hole w/ water, how long does it take to drain?

..If it is still filled w/ water after a day, then that could be a big part of the issue..

Water drains away in under 5 hours?  soil is considered well draining / less likely to create an environment ideal for root rot issues w/ any plants that might be more susceptible to it under wet soil conditions.

[Marjolein]

Do I have to fill it full? I put in about 4 inch of water and it drained pretty quickly, 20 minutes.

[Silas_Sancona]

2 minutes ago, Marjolein said:

Do I have to fill it full? I put in about 4 inch of water and it drained pretty quickly, 20 minutes.

Definitely don't have to,  but even filling half way will help determine how well it drains.  Draining off 4" of applied water in ~approx. 20 mins does sound like it drains well though, ..so that is good..

You mentioned Mangoes..   Generally, they prefer a soil pH in the 5.5 - 7 range, which is considered neutral ..or slightly acidic.., to slightly alkaline..  Can be more challenging to grow if your soil leans heavily alkaline ..A soil pH above 7 is considered alkaline. 9 or 10 would be extremely alkaline, as would a soil reading below say 4, which would be pretty acidic.

You'd also mentioned Washingtonia  and how it is doing well, compared to some of the other plants mentioned.  That particular palm Genus originates here in the Southwest U.S. and nearby areas of Mexico in areas where the soil leans quite alkaline, so it's tolerance to such soils would make sense..


If the option is available to you there in Aruba, you might consider doing a soil test, just to get a baseline idea on your " raw " soil conditions ( how alkaline or acidic it might lean ) 

Some soil tests can also tell you what elements / minerals are present in the soil / how much or little of something is in your soil  ..Say if it is heavy in Calcium, or Iron, ..or some other element.  How much of X mineral(s) are present in your soil can give you an idea on what might be missing ..that would be essential for proper growth of whatever is being planted..

A soil test will help guide you in how to proceed in amending it, if you'd need to   ..Say if it leans too alkaline for instance..

[Marjolein]

It’s PH is 7,2

[Silas_Sancona]

30 minutes ago, Marjolein said:

It’s PH is 7,2

7.2 = running a bit more alkaline than would be ideal for any plants which have a tougher time growing in that type of soil. ...The Mangoes, the Prichardia  perhaps. 

  Adding elemental Sulfur  ..and organic compost are two things you can do which will help bring the reading to within a more neutral pH range over time.

When you plant, would mix whatever compost or ' good soil you use  with some of the native soil so you don't end up planting in a bathtub ..Bathtub = pocket of good soil, surrounded by not as ideal soil any roots will have a tough time spreading into.

60% " good " soil / compost,  to 40% not-as-ideal " native " soil  would be a good ratio for what soil you backfill with after planting.

The more you can coax the roots to grow into the " not as great " soil, the better..

After planting, you can start working the soil from the top down by spreading down a layer of leaves / other organics, and applying some Sulfur occasionally to build a good layer of organics which will be worked into the native soil by earthworms and any other soil dwelling insects / microbes over time.

A bit of warning.. If it available there, would avoid using Peat Moss as a soil amendment option if possible.  For whatever reason, when Peat Moss and Limestone / Calcium -heavy soil types are combined, some chemical reaction that occurs between the two  can cause the peat to quickly decompose into oxygen depleting muck., which is a big invite for root rot problems. 
 

[Marjolein]

Thank you for the advise, when we digged up the current soil we took out the large rocks and mixed the remaining with 2 bags of cow manure and also one sack of bbq bricks. I read somewhere that the bricks give healthier plants, these contain sulfur if I am correct. I was planning to use potting soil also to mix/or place as a top layer. Maybe better to mix it in the existing soil.

A local landscaper advised me that for the lower layer I should use sand from the beach for drainage, what do you think?

[SeanK]

Could plant on a berm

[Marjolein]

Btw not sure if they sell Peat moss here. There are only 2 stores where they sell landscaping items. I will check

[Marjolein]

@SeanK not possible, my dogs like to dig😀

[SeanK]

Just now, Marjolein said:

@SeanK not possible, my dogs like to dig😀

I have that problem with squirrels and BLEs

[Silas_Sancona]

14 minutes ago, Marjolein said:

Thank you for the advise, when we digged up the current soil we took out the large rocks and mixed the remaining with 2 bags of cow manure and also one sack of bbq bricks. I read somewhere that the bricks give healthier plants, these contain sulfur if I am correct. I was planning to use potting soil also to mix/or place as a top layer. Maybe better to mix it in the existing soil.

A local landscaper advised me that for the lower layer I should use sand from the beach for drainage, what do you think?

I'd imagine sand from the beaches there would be lean Alkaline due to its natural limestone / shell and or greatly degraded Coral makeup ..so adding it would only increase what you're out to remedy as far as the pH of the soil..  As odd as it might sound, if the sand there is really fine, it can hold too much water as well.. 

Cow manure can be a great soil amendment,  just be sure it is composted / has sat out in the open for a few weeks  since fresher Manure can be too " hot "  ..IE: containing high amounts of salts, which can burn roots.  As it is allowed to sit out and " cool " salt content in it becomes less / is leached out.

The BBQ bricks,  would that be similar to Lava Cinders? ( Something people use in fire pits here in the U.S. ) ..or actual bricks?..  If Lava Cinder, ..chunks of it,  yes, that could be used to help the soil drain well. ..could also contain some sulfur,  depending on where it was sourced from.

If they're actual bricks, only way you could use them is if they were smashed into smaller chunks.. I'd wonder, since they're bricks, how much Lime is present in them.. Lime is essentially crushed Limestone, which would raise the pH in your soil.


As far as removing rock from any planting holes?  Doesn't hurt removing some, to give new palms / other plants some space to stretch out,  but,   if you look at habitat photos of various palms / other plants native to the Caribbean, and/or arid regions of Mexico and Central America, a lot of them shrug off life in really rocky soil.

In Baja for instance, Brahea armata  can often be observed growing in areas that are essentially giant boulder fields.

As long as there are spaces of soil between larger rocks in the overall soil, roots of plants will find their way through / around the bigger rocks.

 

[Marjolein]

So, I will leave the beach sand out then and place leaves, going to fill the bath tub tomorow and see what happens

[Marjolein]

I filled the bathtub about 1/3 with water and it drained within 2 hours, so good to go