Complexity and clay soil

by Carl Dyke

From time to time I’ll post things here from the works of Dyke the Elder (Chuck Dyke). This one is from his series of reflections on Hesiod in collaboration with his friend Yrjö Haila:

Just to fill in some of the blanks on clay soil. Hesiod leaves a lot to be said on the topic. My direct experience with Mediterranean soil is all from Italy, with basically volcanic soil the norm, and sandy soil in second place. Of course we know there’s clay in the area (Crete): it would be hard to account for all the pottery otherwise. The sources simply say that clay was readily available everywhere, with some better than other because of the presence of particular metals.

Clay is also readily available all over my property. In fact, Bucks county is famous for its clay soil. Yrjo is absolutely right about the waterlogging issue so we’ll start there. Our clay soil, left to itself has two attractor states: mud, and adobe — unbaked brick. So something has to be done about it. How much has to be done depends on scale and crop. Acres and acres of feed corn (maize), as well as sweet corn, are still grown all around my area, even though the dairy farms have all but disappeared. Probably by now everyone knows what varieties to plant for high clay conditions, so the corn is successful most of the time. But for obvious reasons, either excessive wet, or drought, or both will give you a bad year. The excessive wet is worst in the Spring, because you can’t get your equipment into the fields to prepare them. There’s hardly anything more character building than getting your tractor in up to the hubs in waterlogged clay, and having to somehow pull it out. So the farmers are always moaning about the “late Spring”. The droughts are a late July and August phenomenon. Even if you’ve been lucky enough to plant your corn in good time, and it’s thrived to the point where it’s knee high or taller, midsummer drought can stop its growth in its tracks. Of course irrigation is an option – but watch out. If you irrigate and it then starts to rain, you may not be able to get your equipment into the field for harvesting.

One of the most conspicuous consequences of climate change around here is that, in effect, the seasons have precessed a month. What you used to be able to do in March, you now do in April; and what you used to have to do in October can now wait until November. (I’m writing this on March 19. Yesterday I tried to get some things done outside, but the ground is still frozen, and the temperature below freezing.) As we’ll see in a moment, I can wait, though not patiently, but the farmers are already getting edgy.

About five years ago it became obvious that if I was going to be able to get a good start in the Spring, I’d have to do something about the excessive wet. It was showing signs of being the new norm. Now, it has to be remembered that I’m growing things on a significantly different scale from that of the farmers. Strategies are available for me that would make little or no sense for them. So I dug a drainage trench across the bottom edge of the garden: deep enough to affect the drainage from the plot, and in a position that would considerably increase run-off. It’s made a big difference: several weeks, I think. Sure enough, the excessive wet has become the norm – something I can reasonably count on. We’ll see in the next month or so ….

However, the best thing I could do, at my scale, was improve the clay soil by adding large amounts of organic fertilizer. In the old days, especially when there were many dairy farms, the farmers could do the same, as Hesiod could have done. These days they use chemical fertilizers almost exclusively. Thus they lose the contributions to soil texture that organic fertilizers provide. But what with all the manure, compost, and organic mulch I use, I’ve been able to reduce (over forty-odd years) the clay-ness of the soil, as it were. It doesn’t make as good adobe bricks as it used to, but roots have an easier time growing through it. The good black dirt is by now about 8 to 10 inches deep in the garden.

Now is where we have to start to think of the “non-linear dynamics” of this whole situation , where the phrase “non-linear dynamics” means, for present purposes, that you can’t do something straightforward to fix one problem without affecting (and often causing) other problems. For, that wonderful 100 square meters of black dirt is, in effect, a shallow well within the surrounding field of clay. If you were a drop of water, where would you want to live? Well, the point is that the improvement of the soil exacerbates the wetness problem even as it helps with the clay-ness problem. It’s well worth it; but it starts another round of improvements we’ll get to in a minute. First, a parallel non-linearity:

Clay soil is naturally very acid. Some plants like that, or don’t mind it much; others hate it. On balance, clay soil is too acid. Adding all that organic matter makes the soil more acid still. So you find yourself buying a whole lot of powdered limestone, and spreading it around. Fertility of clay soil – the kind of fertility you really want – depends on lime. Since it dissolves easily a lot of it runs off with the drainage, reducing the efficiency; but the grass below the bottom of the garden is nice and green (good for the mulch, so you get back what might just have drained away). So, you can’t deal with tilth and fertility without increasing your drainage problem, which has to be addressed further. This leads to the final two important moisture management strategies: hills and valleys, and mulch.

We return to the shallow well filled with good black dirt. The ground water slowly oozes in from the clay field outside, gently slides from the high to the low side of the garden, and, to some extent, drains into the ditch; but not nearly quickly enough, especially during really wet weather. Furthermore, the wettest times are early in the season, at planting time and just after, when the plants are most vulnerable to being swamped, and, in the worst case, to rotting out. So, after I’ve tilled the garden I get out the hoe and build a system of ridges, in and upon which things are planted. The tops of the ridges end up about a foot above the low stretches between them, but settle a few inches over time. The bottoms of the holes into which the young tomato, eggplant, and pepper plants are set are about 3 or 4 inches above the low stretches. Beans are seeded a little deeper than you’d plant them on flat ground.

A short way to put the point of the system of ridges is that the aim is to buffer against extremes of wet and dry. Tomatoes, for example, develop one kind of vascular system under dry conditions, and another under wet conditions. You can tell that from the texture of the stems. The dry weather stems don’t work well in wet weather, and vice versa. So you don’t want the tomatoes to have to try to switch back and forth between the two kinds of stems. With the ridges, my tomatoes start their major growth under moderately moist conditions, and, as you’ll see in a minute, live their maturity and fruit production under moderately moist conditions. The same holds for the beans and everything else. Occasionally, if the time after seeding brings no rain, I have to keep the seeds on the tops of the ridges moist: a couple of watering cans usually does the job: no extensive irrigation.

Meanwhile, the grass in the field and the lawn is growing. It gets cut and dumped into the garden: first in the low stretches then over the ridges themselves. This doesn’t affect the drainage, but, obviously affects the amount of evaporation considerably. I mulch four to eight inches deep. That’s the last part of the puzzle. The result is that I never have to do a whole lot of watering, sometimes if it’s really dry the squash are happy with a bath, and sometimes I never have to water at all. By the time dry weather comes, of course, everything has sent roots all over the place, well below the surface of the low stretches. Under the conditions I’ve created, the clay down deep can actually become an ally, holding water, and releasing it slowly. My friends the earthworms do the rest.

Well, isn’t that a long song and dance just for a little garden! Yes. It takes time and patience to write it down; it takes time and patience to read it; and it certainly takes time and patience to do it. But that’s what it takes to deal intelligently with a complex system of interacting and largely competing requirements and problems. It’s also important to see that the song and dance it takes me to get things right is particular to my circumstances. The farmers growing corn couldn’t, and shouldn’t do what I do. Then, there are really good gardeners in my general area who do things differently. For instance, you may have heard or read about the (originally French) “raised bed” system. Some gardeners around here have come to use that system very successfully in their circumstances. Isn’t that what I’m clumsily groping for? No. I’ve thought a lot about using the system. It has some real advantages. For instance it’s a lot less work than what I do (especially if you can get someone to make the raised beds for you). But I don’t move to it because it doesn’t answer complexly enough to the tangle of interacting requirements and problems I have. The people who use the raised bed system “swear by it”. I’d probably swear by it too, in their circumstances. But one size doesn’t fit all. That’s one of the major messages to gain from the study of complex systems, even little ones like my garden. Yrjo and I have been thinking together about such things for a long time now, so the best possible example of one size not fitting all is to compare my account to his account to which this is appended. What he knows, and what I know, is that he’d have to be crazy to try to manage his garden the way I manage mine.

While particular solutions don’t travel well in complex circumstances, the overall message – that they don’t travel well — is itself pretty general. I just read a book that documented the same point as it’s sinking in among people who worry about foreign aid, and look for new ways to make it more efficient and increase its staying power. The message is a frustrating one, for obvious reasons. The task of “finding a solution” gets dauntingly hard at the scale and scope those people work. If you think of throwing money at problems as you’d think of pitching baseballs, then it might occur to you that not all hitters were the same. So finding a pitch and a location that worked with one hitter might not convince you that you ought to throw the same pitch in the same location to the next hitter. Baseball is usually more complex than that – unless you’re Sandy Koufax, and never have a bad day.

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