They say adding sand to clay soil yields cement. Maybe sometimes. But based on a highly unscientific experiment in my back yard, not always.
The warning about sand pops up here and there all over the internet, often coming from university Extension offices. The one in Colorado for instance, says flat out, “Don't add sand to clay soil,” predicting a consequence that would make any gardener quake in her gardening boots: “this creates a soil structure similar to concrete.” A specialist with Ohio State University goes even further, saying that the result is usually “a disaster.”
Now, I have a personal stake in this issue, because I spent more hours than I plan to confess (unless you pack me off to Guantanamo) working sand into soil last fall. I call it soil, but that’s a misnomer. It was clay, and the fact that I actually bought it—paid someone to put it into my raised beds—makes me furious. I just can’t decide who I’m madder at, myself or the idiot who sold it to me as “loam.”
Didn’t I notice that it wasn’t the highest grade stuff? Sure I did. Staring at it afterwards, I thought, this was a mistake. Staring at it with me, a good friend said, Send it back. But anything decent was beyond our budget, so, fortified with Mel Bartholomew’s original Square Foot Gardening book, I set out to “improve” it instead.
Every year I dug in compost. I tried little clay pebbles, and peat moss, and gypsum. (Groan. More about that another time.) Every year in the spring I thought, this isn’t so bad! And every year I watched the “soil” harden over the summer, despite the constantly increasing worm population—the only reason it drained at all, I’m convinced. Last August, when it took all my strength to sink a trowel into it to dig out carrots (and that was using two hands), I’d had enough.
It was time to get serious. Since a good loam has at least 30% sand and my soil had way too much clay, the solution seemed clear. I would add sand.
The sand I had access to—stuff my husband picked up from an abandoned building project—contained pebbles galore, so first I screened it, tossing the pebbles on our driveway, Then the real work started. This sand didn’t merely get spaded in. It got mixed. By hand. Bucket by bucket, I stirred sand into the heavy dirt, breaking up clods of clay, squashing them flat on rocks and kneading sand into them. Sometimes I used a hammer on them. By November, I was working under a greenhouse of sorts, trying to finish the four by eight bed I’d started on. Along with the sand, I added peat moss, compost, and slow-release organic fertilizers.
Sometime during the fall, husband Steve brought home the news that sand, especially fine sand, could cause clay soil to turn to cement. Great. Yet I continued. Why? Well, first of all, because I’m stubborn, I guess. (It’s a question of character.) But frankly, I didn’t believe that doing this could backfire so completely. My guess was that most people didn’t work sand in as thoroughly as I did. (This seemed a safe guess.) Or they didn’t add organic matter as well.
When I was researching the unbelievably long lawn article several months later, I ran into the sand-causes-cement claims myself, including the two quoted above. Those aren’t the only ones. They gave me a few bad moments, but it didn’t make sense that adding sand would make rock-hard soil harder. And it didn’t seem possible that my soil could get worse. Time would tell.
It’s October now, a full year since I went full-bore on the sand amendment. Since then, I’ve added nothing to that bed save a thin layer of compost. I didn’t even mulch it (gulp), and since hail took out so many of my plants this summer, a lot of that bed has lain open to the elements for several months.
Yet it’s soft and loamy. Easy to dig, it crumbles willingly in the hand. I wish you could feel it, because that’s the only real evidence. These pictures do not do the trick, I know, but they’re all I’ve got, so here goes:
The photo at the top of this post shows soil taken from the bed that got the sand treatment. The one below shows soil from another part of the garden, where I’ve planted several times, adding other amendments, but never sand.
I’m squeezing the untreated soil sample, but it still holds together. The other, treated, soil crumbled in my hand before I could squeeze it.
Since I’m not much into conspiracy theories and can’t come up with a reason why extension agents at four or five universities across the country would lie about the effect of sand on clay soil, I conclude that sand really does make some clay soils harder. Why? And why not mine?
It could be a difference in the soils themselves, or in the sands added, but I suspect that it’s at least partly a difference in method. Perhaps sand has to be integrated very thoroughly to improve drainage in clays, or perhaps it has to be used with plenty of organic material as well. I’m not sure.
I am sure of one thing: I’m sold on sand.