Adding sand to clay is risky at best. How big of an area is this?

tj

It is my backyard, not too big, 100 square meters. I want sand to make up more than 50% of the soil. Clay is very frustrating to work with, and plants do not grow that well...

Not a well-advised idea! What do you mean by 50%? To what depth? Adding a mere 3 inches of sand would require 10 cubic yards and that is barely scratching the surface!

For sand to be a reasonable amendment for a clay soil, it needs to be very coarse - closer to the texture of grit rather than sand - and added in significant quantity. Deviation from this "formula" is unlikely to produce desired results and instead just produce adobe.

Have you considered adding organic matter instead of sand? Its properties are far superior to lighten a heavy clay soil, which is why it is recommended for that purpose 95% of the time.

I considered adding organic matter, which is what I am doing in addition to sand, I will only incorporate sand in the top 12" of the soil, it would take alot of sand, but if that is going to fix the issues of compaction and drainage forever, then that is okay. Organic matter may be the best solution as you say and as I have understood from all gardening sites, but every time I add it to the soil, it starts out well, and within a couple of weeks, the issues appear again with compaction and waterlogging. I am using builder's sand, kind of coarse and gritty. Cost is not an issue.

In order to have 50-50 sand and soil to a depth of 12 inches you need 12 inches of sand. Put a foot of sand in a bucket and try to work that into an area the footprint of the bucket down a foot and you’ll know what your up against. And that’s not even considering how it will change the grading.

tj

Sand to clay soil is a garden myth. Sand will combine with clay to make what acts like concrete.

https://laidbackgardener.blog/2021/03/11/garden-myth-add-sand-to-lighten-clay-soil/

Well, yes and no, Sherry. The 1:1 ratio is considered ok but that requires a dauntingly large amout of sand. From the U of Illinois:

”To create a real change in a clayey soil structure, you would need to add a 1:1 ratio of sand to clay. Considering the actual volume of clay soil underfoot, that equates to a lot of sand.”

tj

Seems to be unrealistic approach if done all at once! I am going to start with adding 6"-7" sand and tilling that in. Clay seems to never dry out when wet and once it dries it is concrete hard, I think no matter what damage sand causes, it would never become worse. Any ideas would be much appreciated.

Some grit sand can be helpful.... but too much sand don't help much if all there is otherwise is clay. You need some serious organic matter in that mix to feed your soil, add tilth and aeration capability to the soil. You could take a season or two and plant in your organics- deep rooted suff to break it up and bring deep nutes to the surface, green manures to help bring in organic materials.

Also, if you use a sand calculator to measure up a 10x10 m square just six inches deep, you would need 25 tons of sand to start a sand:clay ratio. Thats a lot of truckloads of sand. And it woud likely raise the level of your garden a lot. While it might sound like a good idea to help, in the long run it can make compacting worse because locks in with the clay an silt, and increases the lockout of air pockets and tilth over time.

How much compost are you adding at a time? IF you are willing to order up several truckloads worth of sand, try ordering up a few truckloads of compst first. Maybe a couple loads of clean quality topsoil that is not heavy in clay would help too. Don't overwork your soil- overtilling can help promote compaction.

Clay is very frustrating to work with, and plants do not grow that well..."

There are a wide variety of plants that are perfectly happy in clay soils. Instead of attempting the Sisyphean task of completely re-doing your soil composition, you could instead just add some organic matter and revise your plant palette.

Where are you located and what are you actually trying to grow?

Adding sand to clay will not "make what acts like concrete". Sand is added to an adobe mix to keep the adobe from cracking and to make it easier to get a fully wet mix. Adobe, also called cob, will break down much easier than concrete and can be reused to form new bricks/blocks.

I agree that adding organic matter is the way to improve clay soil.

I hope it works out for you, but it was a total fail for me. It sounds good, but doesn't work. The only thing that works is lots of organic matter twice a year. Cardboard over the soil with mulch on top.

If you are determined to do it, go ahead. It will not work, but you will find that out.

There are many different types of clay. Clay just means the soil is mostly made up of tiny grains. Whether adding sand is a good idea depends a lot of the type of clay you have.

I have a silty clay soil and adding sand helps with drainage and definitely does not form anything close to concrete. If adding a small amount of clay, it just disappears into the mix. if I add a lot, the clay/silt tends to form clumps and the sand sticks to the surface and fills in between. The roots grow through the sand into the balls of sand/silt for nutrients. So I get good draining soil that is also good at holding water and nutrients in clumps. Not bad at all.

I agree that you should test a small area first and see how it works out. And adding organic matter is a good idea regardless if you also add sand.

Hey, guys. been so busy, and it was such an effort doing half of the area only! I want to reassure you tho, the result is quite satisfying, better soil handling and easier to plant in it as well, I was concerned , and it might be the type of sand I used, which is a type of coarse builder's sand. will let you know how things turn out with my first crop. Have a good one.

I added about 2½ to 3 inches of medium sand to my silt loam gardens. I also added about 3 inches of spaghum peat moss from a local pit and mixed it with the top soil...about 7 inches....tremendous soil to work. That has been several years ago and it is so nice. I also added horse manure and mulched leaves.

Heavy clay needs sand. Sand needs clay. Organic matter is great too. Peat moss is instant organic matter. Try a small area. I mixed it with a rototiller.

I would suggest compost rather than peat moss, unless you are in a peat mining area, which most people are not. Compost is usually made close by, from local materials. It also contains more nutrients and beneficial microbes than peat moss, and it doesn't lower the pH (unless you need that!).

The problem with doing this in parts is that if you get below about 1/3 sand, the mixture does begin to behave like concrete when it's dry. The sand is taking the place of gravel ('aggregate' in concrete lingo) and the clay is the cement. If the portion you did with half the needed sand is OK after it settles, is wetted, then gets hot and dry, then I'll be the first to congratulate you.

What I did was to raise my gardens with a local sand/silt/clay mixture that is more balanced, along with lots of compost. If you can find a silty sand, you'll get a real loam rather than sandy clay.

Good luck and let us know how it works out.

Instead of buying sand and/or compost and doing all that mixing buy a soil that already has the properties you want and dump that on top of the existing soil, plant in it without mixing the new and old together.

Building healthy soils? – The Garden Professors™

Other than building raised beds I don't import soil and very little then. I can find ample free material for composting without buying compost. I'd like to share a couple of things I do to compost large quantities using minimal equipment and labor. I found an old livestock feed "hammermill / grinder" a few years ago for 10% what a commercial chipper/shredder would cost. It's even equipped with a bagger which I find really handy. I use a push mower with bagger to pick leaves up rather than rake and often dump and run mower over bagged leaves picked up on the curb. Surplus (reserve stock (: ) of chipped wood and shredded leaves are stored in wire corrals and 8"x16" concrete block bins. I don't spend much time watering or turning the material and only add N sources if I'm lucky enough to find more than needed for active composting at the time. With only an occasional splash of water to supplement rainfall, chip and leaf volume is reduced 20% over a period of 6-8 months,mold and rot has them well on their way before mixed with greens and being turned and watered regularly.

Finally getting to tight clay soil amendment. Texas has a large expanse of black soil that shrinks and expands so bad that home foundations are commonly damaged. The shale parent materials have produced a significant extent of clayey soils having high shrinkswell properties, including Houston Black, Heiden, Frelsburg, Bleiblerville, and Latium soils. Cracks wide enough to fit a man's foot in is common during dry weather. When it rains enough to restore moisture in soil cracks completely close. A few years ago in addition to my yard I chose places on my property that would be good homesites. When selling lots in Texas every mature tree adds dollar value . A single mature Pecan or Oak can easily add $20k compared to a treeless lot in same neighborhood. I feared working organics deep into soil around trees would damage roots so I filled cracks with organics. Wide cracks were filled with wood chips,narrower ones with dry compost shredded fine. After 3rd year few cracks were wide enough for chips so I've only used shredded dry compost topped with a small amount of sand since. If anyone has similar soil and wants to try this in their yard near trees I suggest doing as I did in my yard incorporating liquid fertilizer and following up with adequate irrigation.

Thanks everyone, I would like to mention that the soil I have is 30% silt, 60% clay, not too bad, but it does not drain as it should and stays wet for so long that the little trees that I planted started to wilt. I do not have silty sand available and I am not sure where to find that, nor do I have any source of loamy soil. I am still adding more sand and composted manure. Let's see how it goes, any I will keep you updated.

FWIW, here is my opinion.

Adding sand to clay is a very difficult thing to do.

The amount of sand needed is huge. The type of sand needed for good results is hard to get. (Builder's sand is very fine and therefore unsuitable.)

As everyone is bound to have said already, organic matter is what you need, and lots of it. Over time, you will end up with a nice soil.

A clay-based soil is what I have. I like it. Some of the organic matter I've added over the years is: horse manure, sheep manure, fallen leaves from deciduous trees and grass clippings. The amount of this would be rather large as I used to collect manure and leaves in our trailer. I've never added sand.

Since you are mentioning poor draining and water logged soil, I'd be concerned about you tilling to a constant depth and ending up with just a bathtub effect if you land isn't on a slope of sorts.

I believe studies show a gradation of soil types (in regards to drainage) is better then having perfectly draining soil sitting on top of poor draining compact clay.

I end up double digging my new beds since my soil is just clay fill dirt brought in to level the property originally. Once I get to the depth I want, I use a spud bar to break and crack up the bottom and side walls of the bed. A tiller can't do this and you can end up in a bad spot.

The slope is an important point. So is the fact that when you dig in amendments the addition and the fluffing effect raise the soil about 8 inches when I dig a spade deep. Some folks with raised beds don't have that much rise above their original soil level,

I have read several old books about soil. Sand is recommended for clay soils and clay for too sandy soils.

I have amended about 7,000 sq. feet with sand and peat moss from a local bog.....tremendous change in the soil instantly. My soil was fairly good to start with and needed only about 3 inches of sand + about 3 to 4 inches of 90% assay spaghnum peat moss. Why all the fear about concrete?...try a smaller area. Yes other organic matter is desirable also....been there, done that.

I live on clay soil and lost a few saplings when I first started out. I learned from local experts that trees planted in clay should be planted with about 1/3 of the root ball above the ground, and soil mounded up around it to cover the root ball from all sides. Also, if you are amending the soil at all (some say not to but I can't help myself), the hole should be a wide, shallow dish, tapering out to the surrounding level, rather than a deep cylinder. Cover the root ball well with mulch so it doesn't erode away and expose the roots.

This allows the tree to get moisture but not be sitting in a puddle of mud when it's very wet outside. It's worked quite well and we have huge trees now to prove it.