Dirty Business: Soil pH Testing

Whenever I would hear about pH testing garden soil, the header image is what I would imagine:  a sterile laboratory environment where all sorts of crazy—and expensive—equipment is used to determine if the pH of the soil needs to be adjusted by a micron or two.  This was one of the reasons why we haven’t done soil testing in the past—because it just seemed too intimidating.  We’ve never been particularly hardcore gardeners.  We’ve always kind of muddled along, figuring things out as we go.  Also—and this is no small thing—I’m a Cheap Bastard^TM which means that we’ve also done a whole bunch of our gardening work without the benefit of many of the nifty tools that lots of gardeners employ.  Over time, this has meant a couple of things to me:  the first is that it is entirely possible to garden successfully without all the fancy stuff.  The second is that, while the fancy stuff isn’t necessary, it certainly does make things a little easier.

In this particular case, we’re going to be talking about soil pH and how to test for it.  Now, I know that pH is important for the health of the plants, and that too much acidity or too much alkaline is generally going to make for poor health and poor yields.  However, that doesn’t mean that I would actually go through the trouble of testing the soil.  After all, we’ve always been able to get good yields from our gardens over the years without testing.  Oh sure, every year there would be one set of crops that would fail spectacularly—cucumbers, eggplant, peppers, etc—but the other plants would always manage to produce well so I just didn’t want to deal with it.  Well, not anymore, friends.  Last year’s fiasco with the eggplant convinced me that it’s time to start engaging in this very simple garden prep task.  So, I went to the store and got myself a battery powered soil tester.  I did this primarily because I hate trying to decipher the subtle shades on the testing paper when comparing it to the reference strip.  I’m not color blind, but I’m not really great at dealing with minute differences in shade.  Plus, the battery-powered tester wasn’t particularly expensive—about $20—and I figure that it will eventually turn out to be cheaper in the long run than buying a new paper testing kit every couple of years.

First, let’s take a look at the dirt:

That might not look very clean—and it isn’t.  Most of what you’re seeing there is a top layer of manure that we spread over the beds at the end of the growing season last Fall.  Plus, you’ll notice there are some ashes and chunks of charcoal scattered around.  We get the manure from a neighbor a few doors down.  They used to have a horse and a donkey for a number of years, but the animals went to a nice farm upstate a couple of years ago.  But all the manure is still there, and it’s been mellowing and breaking down into a beautiful, almost soil-like consistency which is perfect for a garden.  Some kinds of manure are better than others, but the main thing to keep in mind is that no matter what kind of manure is used, it must not be fresh.  Fresh manure will shock the plants and kill them.  Anyway, we started spreading it on our garden just a couple of years ago and the difference was immediate.  Last year’s yields were off the charts and the plants were super strong and healthy.

Regarding the wood ash and charcoal, this provides a double-whammy of soil pH balancing and fertilizing benefits.  For pH purposes, the ashes pull the soil toward the alkaline end of the spectrum, which is what most plants like.  Wood ash also contains two of the three components of fertilization:  potassium and phosphorus.  Further, the pieces of charcoal are particularly important.  When mixed into the soil, these provide a means of stabilizing the moisture in the ground by soaking up rain water for the roots to pull from over time.  This is a centuries-old technique that was used in more arid climates by civilizations that either couldn’t irrigate their crops, or simply hadn’t learned how.

There’s also some crap in that dirt—but not the good kind.  There are stones and leaves and sticks and some other garbage.  Our house is built on a hill, which means that it was pretty heavily landscaped using terracing and stone retaining walls.  The previous owners used these landscaped terraces the way most people would:  by planting shrubs and flowers and other useless plants.  They used that ghastly red-dyed wood mulch, large-stone gravel, and generally didn’t bother with maintaining the condition of the soil.  So, by the time we got our hands on it five years ago, the soil was in terrible shape.  It was very sandy and had almost no nutritional value.  Fortunately, this is nothing new to us in all the places where we’ve lived, so we’ve been working to get the soil back into shape and it has come a long way in a short time.  All that’s to say that the garbage in there like the stones and other detritus is so pervasive as to make it pointless to try and clean it all out.  I pick a few of the bigger rocks out each year and toss them, but I know it’s something I just have to work around.  The moral of this story is that your little patch of dirt doesn’t have to be perfectly pristine.  It can have defects—even really bad ones—and still be a good place for growing vegetables.

Before I test the soil, I need to turn the ground in a few sections of the garden where I’m going to be planting first.  If the test is going to be accurate, then I need to make sure that all that manure and wood ash isn’t just sitting on top.  So, I took a shovel and turned a couple of sections over repeatedly until everything was well-mixed.

The ground isn’t yet thawed enough for a full-blown ground turning all over the garden.  There were definitely some frozen areas which made themselves known when I was selecting spots for turning and testing.  Plus, I’m not testing all over the garden today.  For now, I’m just going to test the areas where the seeds we are starting indoors this weekend are going to wind up getting transplanted at the end of May, which are the various and sundry peppers and a couple varieties of eggplant.  Yes, I know I said I wasn’t doing eggplant again this year, but when I was going through our seed inventory to figure out what to order, I found three packets of eggplant seeds; and I am incapable of just throwing them out.  It feels like a waste, so I will find a way to deal with the eggplants again this year.  One thing I plan to do is give away a bunch of young plants to our neighbors when the plants are ready for transplanting, which should help me burn through the inventory a little faster.  But, rest assured, once these are gone, I will be free from the tyranny of constantly figuring out how to eat all that damned eggplant.  If you’d like some, just drop by the house and I will gladly hand you as many as you’d like.

But I digress.  Over the next few weeks, I’ll test other areas of our garden to see how the pH looks compared to what we’re planning to put in the ground based on the diagram we made in January

The process for testing soil pH is the same whether you’re using paper strips or a super high-tech battery powered tester:

1. Fill a small plastic container with some of the newly-turned dirt.  Yes, you can certainly do the pH testing directly in the garden, but this method is a little easier.
2. Put enough distilled or filtered water in the container to make mud.
3. Use your pH tester in your mud sample.

When I say “mud”, this is what I mean:

The first place I tested was the spot where the eggplant are going to be.  According to the information on the seed packet, eggplant prefers soil between 6.2-6.8 pH.  This first patch of the garden is right on the money—about 6.6:

The test for the peppers, however, showed me that the dirt is just a wee bit too alkaline:

This is reading around 6.9 and peppers of all stripes (sweet or hot) prefer 6.5.  This isn’t enough of a difference to ring any alarm bells, but what this has shown me is that the wood ash I was planning to spread in the pepper patch shouldn’t go there this year.  If I do, I run the risk of tipping the pH over 7 and that could be a problem.  Instead, I know that the grass mulch that we use during the growing season will add more acidity to the soil and bring that pH down a bit.  I can also mix in some of the fallen oak leaves which have yet to be raked up and disposed of.  Oak leaves won’t immediately bring down the pH, but as they decompose over time it will have the intended effect.  Now, had I not decided to start pH testing this year, I would have very likely doomed the peppers, so this latest nudge into hardcore gardener territory is already paying off.

I also tested the ground where the blueberry bushes are.  Blueberries, unlike most other plants, actually prefer a fairly acidic soil—around a pH of 5—and we’ve not really done much of anything with the ground in that area because there’s a bunch of other landscaped bushes that I haven’t yet figured out how to replace with something useful.  I’m betting that the soil will be acidic because of all the wood mulch that has been there over the years (we switched from that hideous red mulch to a natural brown hardwood mulch).  So, I ran my test and nailed it:

One thing you may have noticed about this tester is that it also tests the levels of soil fertility.  However, it doesn’t actually distinguish between phosphorus, potassium and nitrogen which makes it less useful.  I did decide to try the function out and it told me that our very nicely cared for garden dirt was not fertilized enough, while the neglected and acidic blueberry patch soil was just right.  So, I don’t trust that shit at all.  One of the characteristics of acidic soil is an overabundance of nitrogen which is probably what that fertilizer reading is picking up—but, again, without the ability to determine in detail how the three fertilizer components are present in the soil, this functionality is essentially pointless.  Fortunately, it’s not that hard to tell how well your fertilizer balance is once the plants are in the ground—and it’s also just as easy to remediate if there’s a problem—so I’m not going to stress about it.

So, fear not the arcane science of soil testing.  If I can do it, I promise that you can do it.