Garden full of high pH building sand. Need advice.

Hi,

I'm planning to plant two fruit tree guilds in my garden in the Netherlands this spring. I've been preparing by removing paving stones where I intend to plant. Unfortunately, I discovered that underneath the paving there is building sand mixed in with the soil in various proportions: Some areas are almost pure building sand with a pH of 8.8, some have barely any with a pH of 7.1 and some have a mix with a pH of 8. I tried removing the building sand with a shovel but I quickly realised it's not scalable as I'd end up having to remove around 5 cubic meters of soil,  plus it's expensive to dispose of soil in the Netherlands.  I've considered some other options:

* choose alkaline loving plants - the issue here is that very few fruit trees tolerate pH above 8. Options would be very limited.

* add sulfur to the soil. This could be promising but it's difficult because the alkaline building sand is very localised. For example, I tested a piece of soil with 7.3 pH that was 30 centimeters away from another patch with 8.8 pH. Could I apply sulfur to such specific areas? Also, this isn't a permanent solution and would require regular maintenance.

* I'm sheet mulching the area before I plant everything. Would this be enough to buffer the plants from the high pH? What about the trees as they'd be planted directly into the soil rather than the sheet mulch.

I've attached picture of the garden with labels showing the situation.

Thanks in advance for any help!

I would just mix all the sand into the rest of the soil especially if its mostly clay.  I add builders sand to my soil because its heavy clay and it helps keep it workable. You might find the alkaline ph is some residual lime? If you have just lifted the slabs perhaps it will wash it out with the rain eventually. So I would mix it all together then test it again after it has rained if its too alkaline I would add some compost to make it more acidic. I would guess you might not need to go as far as adding sulphur to it after that.

What is the soil composition not in the sandy area?

I'm no pro by any means, and maybe this will not work at all, but my first thought would be to dump loads of acidic plant material on the soil and dig around a bit. I suppose you don't have so many coniferous forests in the Netherlands, so maybe pine needles are not an alternative, but maybe, I don't know, ask a grocery store for all their rotting fruit? Maybe citruses would lower the pH a bit, but more gently than sulfur? If you mix it with wood chips it could also help build soil organic carbon to dilute the alkalinity a bit. Just some hugely unqualified thoughts.

Henry Jabel wrote: You might find the alkaline ph is some residual lime? ...

What is the soil composition not in the sandy area?

I was thinking the same thing. It's plausible that some construction leftovers from concrete work were dumped there.

I suppose you could rinse a soil sample in water and re-test the pH. If it rinses out, the pH will drop.

Otherwise, I suggest the best way to deal with very high pH is to dig out the soil or build raised beds over top. Acidifiers like peat moss, sulfur and epsom salts help temporarily, but it's an uphill battle. Or so it has been for me.

I personally enjoy "cut and fill" projects. By this I mean creating something useful out of "cut" away or removal material which makes the "fill" project. In making a garden such as yours, you may end up removing half the sand from your future bed which is the "cut" away aspect of the project. Instead of throwing away that sand, ask yourself, "What are the possible fill projects that will help my space?"
For example, since I live in a sandy desert environment, my use for sand is in building with adobe blocks or cob. You could also make or buy sand bags and fill those bags up with sand. Perhaps you could make the perimeter of your raised bed with these bags. Or you could use the sandbags to make raised bed borders, garden shed, a retaining wall, a patio platform, or a children's fort. The bags themselves can be concealed with a mud plaster (90% sand, 10% clay, mixed with water).
Once you cut out half the sand, mix your remaining sand with garden soil and acidic amendments such as peat (1:1:1 for starters). Compost in situ (such as worms and kitchen scraps in holes within the bed). Plant something like fava beans that will give your sand and peat soil lots of organic material to eventually feed worms and hold some of the water that wood otherwise drain away.

Eino Kenttä wrote:...my first thought would be to dump loads of acidic plant material on the soil and dig around a bit. I suppose you don't have so many coniferous forests in the Netherlands, so maybe pine needles are not an alternative, but maybe, I don't know, ask a grocery store for all their rotting fruit?

This was my thought as well. Maybe fruit/citrus waste from a smoothie shop or juice bar? Coffee grounds in pretty significant quantities? Pine sawdust from a wood shop (not sure about this last one)?

Henry Jabel wrote:What is the soil composition not in the sandy area?

Thanks for the advice!

In the area that wasn't paved, it's sandy loam, so similar proportions sand and silt but not much clay. Does that change your recommendation?

Thanks for the advice everyone! To summarise:

1) Rinse soil sample and re-test pH to see if it drops. If so, pH will eventually drop and all good we're done   Otherwise,...
2) Dig out as much of the building sand as possible. Instead of disposing, reuse in another project.
3) Add acidic soil amendments (e.g. peat moss, coffee grounds, citrus waste, pine, sulfur)
4) Add organic matter/compost to build and acidify the soil, and buffer the high pH.

Does that sound about right?

I would ignore the pH completely my soil is 8.5 with 30cm until chalk in places, pears, apples, plums, elderberries and hazel all do fine, as do raspberries, red and black currents gooseberries and strawberries.  I am not a believer in trying to change the pH of soil, it's something you have to import huge amounts of material every year. What you can do is add more organic matter which will reduce the effect of the pH and don't try to plant rhododendrons or blueberries for example.

Liam Furman wrote:

Henry Jabel wrote:What is the soil composition not in the sandy area?

Thanks for the advice!

In the area that wasn't paved, it's sandy loam, so similar proportions sand and silt but not much clay. Does that change your recommendation?

It might be a good idea to add some clay then if its excessively sandy along with plenty of organic matter.  

While coffee grounds or other organic matter will help raise pH, it's is an old wives tale that coffee grounds are acidic. Fresh coffee is, but once it is percolated, it is basically neutral.

Biochar can range up to 8.5 on PH. and can be added up to 10% of soil. please see how to charge it.

Since it looks like? you have dead soil considering PH is wise.

PH matter less as soil becomes more OM full.

But suggestions above seem wise grow plants that can handle that soil until your soil is active and then as ph and heavy metals become buffered in the soil it won't matter at all or as much in general.

this may help conceptually
most people are talking about dead soil, conventional soil, using salt fertilizers or soil that's barely active

PH Soil and Organic Matter

PH is the inverse logarithm of hydronium to hydroxide ion.

PH in soil doesn't matter if you have a healthy soil biome with high organic matter (OM.)  

PH Meter in soil will vary during day 5 ph to 7 ph back to 5 ph because the PH is responding to bacteria and fungi response to sugar exudates inserted into the soil by the plant roots by raising and lowering the acid base to
solubilize nutrients in the soil to feed the plant.  PH can't be static because then the soil is dead.  PH must change to Solubilize different minerals.

A low PH Soil indicates the tank is empty of minerals because they have been mined off.

High Bionutrient Crop Production with Dan Kitteridge part 2
https://youtu.be/5K1B9X4HGuY?si=-DgLm4ytUgr2DVWf
19:10 mark

Organic Matter Soil PH

Given you have crappy soils or you apply fungicides, herbicides, pesticides or you use synthetic fertilizers, PH does matter.

BUT if you have high fungally dominated bioactive soils with organic matter, PH doesn't matter! Repeating PH doesn't matter if you have a healthy soil biome with high organic matter (OM.)  You must keep that OM high too. Bonus: High Organic matter will isolate and buffer (sequester) high Aluminum and other Heavy Metals in the soil over time.  

PH matters in dead soils and Test Tubes. Soil isn't a test tube.

PH 6.5 solubilized
Copper, Zinc, Calcium

Phosphorous higher