Adding sand .. is it a good idea?

Hi,

In the vicinity of the house we have a 100sqm spot that would be great for a garden but the soil is mostly made of clay, that during the hot summer, will crack quite a lot.

Will it help to dig it, crumble it and mix it with sand (not the super fine one, but the builder type)?

I searched on Google, but I saw quite different opinions. Anyone has any hands-on experience?

Thanks!

Hi Sorin.

I doubt that mixing sand with the clay will give you the results you desire. Adding some sand may help, but, the one of the best ways to loosen up the clay soil is to add gypsum. It's the calcium in the gypsum that is going to, on a microscopic and molecular level, loosen up that clay and make it crumbly. I think gypsum and sand could be a good approach for you. I want to also note that adding organic matter, in the form of compost or decayed leaves for example, will greatly improve the fertility of the clay soil and also help with loosening the clay, and helping it to hold water and not dry out so fast.

I am going to second what James has said, especially about the gypsum and calcium.

I am also going to say that if you don't add lots of humus, the sand and clay will be most likely to seize, that is the two will make a concrete like structure.

I recommend that you should first add organic matter, either compost, manure or straw/hay and you want to mix that into the clay down to around 10 inches.
Once you  have that done you can come along with gypsum (or you can mix it in at the same time for a first application) and mix that in.
Next would be to mix some more gypsum into manure and or compost and lay that on over the surface as a  mulch layer, into which you would sow seeds of cover crop plants to get roots working and the microbiome going strong.

What we are trying to do with a clay soil is provide structures for those superfine particles of clay to cling to, this opens up the tight structure that clays naturally form since the particles are microscopic in size.

Expect it to take you a growing season or two to achieve a good soil structure that lets water and air infiltrate easily and as long as you continually are adding organic matter in mulch form, things will only get better.
Once you have some openness to your soil structure you can think about using wood chips (fungal food) mixed with or on top of compost/manure mulch which you will plant through.
The more you can open the soil structure, the better your microbiome will become and that means your soil will only get better because of your attention to the microbiome organisms needs.

once you can pour a five gal. bucket of water on the soil and it doesn't sit on the surface for more than 30 minutes, you are ready to add some sand to that soil.

Redhawk

Double ditto.  Mulch, mulch, mulch, mulch, mulch.

Clay soil is tremendously fertile ---- IF ---- you regularly add biomass.  Carbon is the solution to hard, lifeless clay.

Clay particals are very small, negatively charged, and "stack" on top of one another.  The best analogy I've heard is that clay particles are like a stack of paper plates.  One stacks tightly up against the next.  Air, water or any form of biota (worm, roots, whatever) have a difficult time breaking into these tightly bonded stacks.  The negative charge helps them tightly "cling" to one another.  That negative charge also grabs onto nitrogen and other nutrients, so it can either be your friend or your foe.

But when you introduce carbon into the system, those long, tightly stacked clay columns are broken up so that water, air, and biota can move more freely through the soil.  Nature does this by dropping a layer of leaf litter on top of the soil annually, even as worms and beetles carry that carbon down into the soil.  Roots punch through the clay in the soil profile and they secrete exudates that feed microbial life and fungal networks.  Year after year, nature finds a way to introduce more and more carbon down into the soil.  We mimic this by mulching heavily.

Would sand help?  If you are putting lots of mulch down, yes, it will change the texture of the soil . . . a bit.  But without carbon, you're just making concrete.  I think the reason people are drawn to adding sand is because it offers the promise of a one-time solution.  It's a false promise, but it's attractive none-the-less.

Thank you all for the answers :D
A neighbor brought me quite a lot of organic material (straws with sheep manure mostly) and I put it on a part of it so lets see how it goes.
I also made 1sqm with sand (a 20 liters bucket) and 1sqm gypsum to see how it goes, as an experiment.

Emphatically no, not a good idea at all, not on its own. Not unless you want an impermeable slab.

I would be interested in seeing the effect of having a sand mixed area alongside the manure and straw-mulched area and gypsum mixed area. Will it basically clump up on itself, while the rest crumbles, to varying degrees, or will the gypsum and/or organic matter mulched areas influence the sand mixed area?

If the effect is visually drastic, as in, if you end up with a giant golf tee shape of sand clay mixture heaving up slightly from increasingly friable soil, please take pictures to share with us.

But keep us posted, and good luck.

-CK

I mixed HEAPS of horse manure, kitchen scraps and leaves into my heavy clay soil, and after it all decomposed and I dug it up it was still looking like typical clay soil!

So JUST mixing stuff I to clay isn’t a solution in my experience. Mulch is what seems most important. A heavy layer of woodchips will keep your clay moist and soft all year round, allowing everything to grow pretty easily. As the woodchips decay keep adding more organic matter and woodchips and your soil will keep improving.

I have fantastic fertile clay soil in winter when the sun’s mild and the temperatures cool. No mulch or additions needed and my yard becomes completely green. But once spring comes around my clay soil seems infertile because it dries into a brick that nothing can grow in and water can’t penetrate. Summer’s impossible. Heavy mulching with woodchips (leaves aren’t enough) is my only option.

Tim Kivi wrote:I mixed HEAPS of horse manure, kitchen scraps and leaves into my heavy clay soil, and after it all decomposed and I dug it up it was still looking like typical clay soil!

So JUST mixing stuff I to clay isn’t a solution in my experience. Mulch is what seems most important. A heavy layer of woodchips will keep your clay moist and soft all year round, allowing everything to grow pretty easily. As the woodchips decay keep adding more organic matter and woodchips and your soil will keep improving.

I have fantastic fertile clay soil in winter when the sun’s mild and the temperatures cool. No mulch or additions needed and my yard becomes completely green. But once spring comes around my clay soil seems infertile because it dries into a brick that nothing can grow in and water can’t penetrate. Summer’s impossible. Heavy mulching with woodchips (leaves aren’t enough) is my only option.

Did you keep that mulch layer moist? Just because materials decompose doesn't mean they were able to leach any of their nutrients into the soil, to do that the mulch needs to have some moisture in it all the time. Clay is a lot like sand, if you are adding things on the surface, they will disappear very quickly once they break down into small particles, to allow organic matter to stick around you have to create structure into heavy clays, this is usually done with lime or gypsum or a combination of the two as well as the organic materials.  Wood chips are a very good addition and will condition clay soils when thickly layered.
The best organic materials are roots when you are trying to turn a heavy clay into soil, so cover crops to chop and drop are a good thing.

I am going to disagree with everyone else.

Yes adding sand can and will help heavy clay soil.

I say this from practical experience. The community I lived at in AZ, Arcosanti, built a volleyball court on top of the mesa. The soil up there was heavy clay that was mostly barren and unable to support any life. To build the volleyball court they dumped a lot of sand they sourced from the river bed. The unintended consequence being. The volleyball court is the only part of the area that needs regular weeding and care now. Volunteer plants have colonized the volleyball court, but are limited to the area where the sand was placed. The sand was just dumped into the area, about 2-3" deep. Not mixed in or anything. But it has made the area a lot better for plants to grow.

That said. Is adding sand the best thing to do? Should it be the only thing done? Are the suggestions others made also good ideas?

I would say adding sand is a good part of the equation, but not the only thing to be done. As others suggested adding organic material, especially stuff with some good fungi mycelium would be a good idea. Adding in sand alone would/will take a lot of sand. Unless you have a good free source of sand, I would say it is not worth exploring. But if you do have a free source of sand then I would add it along with organic materials.

David .. up to now, that experimental patch with sand .. is not like "concrete" but it is pretty loose which feels really nice comparing with how it was. Not sure how it will be in the long term but in the short term seems like a fast fix (I repeat .. I used normal sand for construction works)..

Devin Lavign wrote:I am going to disagree with everyone else.

Yes adding sand can and will help heavy clay soil.

I say this from practical experience. The community I lived at in AZ, Arcosanti, built a volleyball court on top of the mesa. The soil up there was heavy clay that was mostly barren and unable to support any life. To build the volleyball court they dumped a lot of sand they sourced from the river bed. The unintended consequence being. The volleyball court is the only part of the area that needs regular weeding and care now. Volunteer plants have colonized the volleyball court, but are limited to the area where the sand was placed. The sand was just dumped into the area, about 2-3" deep. Not mixed in or anything. But it has made the area a lot better for plants to grow.

That said. Is adding sand the best thing to do? Should it be the only thing done? Are the suggestions others made also good ideas?

I would say adding sand is a good part of the equation, but not the only thing to be done. As others suggested adding organic material, especially stuff with some good fungi mycelium would be a good idea. Adding in sand alone would/will take a lot of sand. Unless you have a good free source of sand, I would say it is not worth exploring. But if you do have a free source of sand then I would add it along with organic materials.

From your description you used a sand mulch layer which held moisture against the clay.
AZ Mesas are a very specialized microclimate and do respond well to laying sand on the surface since the mesas do experience dew fall at night. (I got soaked the time I spent the night on one without a tent for cover.)
The main problem with all clays is that clay is a super fine particle, when superfine particles pack together they can appear to be solid even under 2500x magnification.
I've been to parts of the Mojave desert that were wind swept down to the layer of clay, you could pour water on it and it would sit there in a puddle for hours.
Laying some sand down on the surface and then pouring water on and the water soaked into the sand and was held in place on the clay surface, which then would slowly adsorb the water, once the water hit the dormant seeds, they sprouted as if there had been a rain event.
It was an interesting experiment when we were developing some methods to green the desert back to what had been there 2000 years ago. We had to stop far short of the class goal because the quarter was over and most of us were on to new classes to finish out our degrees.

Sorin Trimbitas wrote:David .. up to now, that experimental patch with sand .. is not like "concrete" but it is pretty loose which feels really nice comparing with how it was. Not sure how it will be in the long term but in the short term seems like a fast fix (I repeat .. I used normal sand for construction works)..

This is the patch where you used sand and gypsum yes?  The gypsum is at least partially responsible for the sand loosening if that is the case.

I don't even remember how many experiments we did in my desert environment remediation class but we spent two months in the desert working on methodology that would work for turning the desert green without any outside water additions.

People around here call our soil clay. It would be more accurate to call it silt. It is derived from limestone. I love growing in gardens where people have added sand. They are much easier to work with (traditional tilling and annuals) than unamended silty-clay. That's with our particular type of "clay", sand, and climate, and with my habits as a farmer. Results may vary in other places with different types of soils.