Soil Testing: Genius or Snapshot of the ever-changing?

That question probably seems crazy to some, interesting to others, or maybe even downright sacrilegious others. After reading a good presentation of how soil tests provide only a snapshot of the soil community, I started to doubt if I should test my soil. After reading about soil amendments, I'm thoroughly confused.

So now I ask with an open mind: Does a macro/micronutrient soil test have strong positive influence in building great soil, or is the chemical make-up of soil constantly changing as microcritters interact with it so that a test is only a snapshot of an actively changing environment?

Give me your best argument for or against the benefit of soil tests!

I’m pro soil testing. I do indeed agree a soil test is a snap-shot of the sample submitted. I’ll do my best to explain a little on why I like soil testing, when I do it, and how I interpret the results.

I think the first fundamental in soil testing is submitting a sample that accurately represents the area desired to be tested. This means taking many, 8 or 10 or a dozen or more individual samples in an area, mixing them together thoroughly, then taking a portion of the mixed samples to send to a lab. Sending a small bag of soil from one hole dug in an area does not represent the area as a whole. Limit the sample to the first six inches of depth.

One lab that analyzes soils may use a different method from another lab. The lab I’ve been using uses the Mehlich III extraction method. It’s good for soils that have a pH under 7. Soils with an alkaline pH over 7 really need a different kind of test in order to have accurate results.

Most labs test for the basic 14 or so elements that “science” has says are needed for plants growing under conventional agricultural methods using petroleum based salt fertilizers. These labs may make a recommendation on how much fertilizer to apply, when to apply it and possibly even how often for a season, depending if a soil sample came with information on what crop is going to be grown in that soil.

I like to do soil tests, especially if I’m starting off and I have no idea what is going on in a soil. I need a baseline to start with. Even if I get a soil test so I can know only the Cation Exchange Capacity (CEC) & pH and nothing else, it is worth it. A soils CEC is its pantry. How much cations the soil can hold. Believe it or not, some soil testing labs don’t provide this critical piece of data. If someone is unsure if a lab does this, email or call and ask the lab if they provide CEC on the report. If they don’t, seek another lab. Knowing the pH of the soil is a clue as to what is going on with the availability of the rest of the minerals, the cations and anions. The Anions, by the way, cling to organic matter, especially humus, which is stable organic matter. Anions don’t cling to soil colloids, only cations will. This is one very important reason of many very important reasons to have ample organic matter in a soil.

With a new soil test in hand, I read the CEC, pH (which hopefully will also note the exchangeable hydrogen), percent organic matter, and the ppm of the minerals the lab identified on the report, and then take any information recommending “fertilizers” and disregard it. Those suggestions are unnecessary and do more harm than good. Armed with this data, I am able to make calculated additions of rock dusts such as lime (the stuff from a limestone quarry, not the bagged pelletized calcitic or dolomite lime) gypsum, soft rock phosphate, etc., whatever may be needed to bring quantities and ratios into balance as recommended by the great William Albrecht, soil scientist extraordinaire. He is the one that figured out mineral balances in soil, such as 7:1 calcium:magnesium for example.

There’s more to it. Glance at a periodic table of the elements. There’s a bunch of elements there. Why is a lab only concerned with a handful of them? I have my thoughts on that, but that’s for another discussion. So elements like cobalt, selenium, iodine, vanadium, yttrium, and almost 75 other elements aren’t mentioned on a soil test, but these minerals play an important role in supporting healthy soil biology, which in turn grows healthy, nutrient dense whatevers that are growing in a soil that contain these trace minerals. Where are these minerals found in abundance and how do we get them in our soil? They come from the sea, and we can put them in our soil by applying unrefined sea salt and/or kelp.

And there’s more to it, the soil biology that makes all these minerals available to a plant,  but I’m going to stop here. This thread is about soil testing, which is about providing data on the cation exchange capacity,  pH, and minerals in a soil.

I find soil testing extraordinarily helpful and recommend it to anyone. It’s important to know what’s already there in order to make calculated, educated decisions on what & how much of a mineral to apply, if needed. Some soils may not need anything, and just need a steward to heal the soil and nurture the bacteria and fungi, so abundant nutrient dense grasses and crops may flourish.

My mind isn't made up, and I'm certainly not against soil testing, but I can tell you why I don't do it.  I'm converting an decent sized area of land, an acre or two, from what was the former land owner's deer plot, to a food forest.  Every area I have "managed", whether food forest, garden, whatever, I do many of the same things.  I put down azomite or Sea-90 or both.  I put down coffee grounds, straw, compost, wood chips, leaves, biochar, and whatever other organic material I can find.  I plant tillage radish and other cover crops everywhere I'm not planting a tree guild or a garden immediately.  Whatever a soil test would show me, as soon as I start on an area, I immediately start adding things that would change the soil from what it is, to what it is going to be.  My method isn't at all scientific, and possibly a soil test would tell me exactly what was needed where.  I don't know.  I know things were growing in this spot when I started, so my assumption is that the PH isn't horrible for plant growth, and I'm doing my best to do all of the things that might be missing.  So far, I'm having results I'm happy with.

I think it depends on your goals. If you are engaged in production agriculture you probably want to test multiple times a year as you get your system up and running so that you can make amendments and monitor the effect. Once you have an established baseline you could test less often just to sort of monitor for changes, especially if you were experimenting with a new crop/amendment/cultivation practice. For high intensity production testing multiple times a year of soil and plant tissue tests can be useful in allowing the farmer to apply fertilizers super efficiently, theoretically $300 in testing in a season could simultaneously save $500 in fertilizer and help produce hundreds of dollars more of produce.

If you are just talking about your homestead/garden, and if you are using the native soil, it is probably worth getting at least one test done so you can get an idea of what your are working with and if there are any major deficiencies and or excesses (I have seen tests where the phosphorus is off the charts and the people were still adding a bit of bonemeal every spring because that's what someone told them you should do every spring, if they had tested earlier they could have saved a bit of money on bone meal) and then you may want to test again at some later point to make yourself feel good about your progress or if you are noticing new issues or if you want to conduct an experiment.

People that proudly never do soil tests, will confess that they will do soil tests when there is something wrong and they cannot figure it out.

If nothing else, I think it is good to "take a few pictures" to have some understanding of the general story.   Does your property have a serious deficiency of something?   A toxic level of excess?

So far it seems like take a test or two, that will give you an idea of what's going on. Then you can remove toxins or correct some obvious deficiencies. Will nature fill in the rest through exudates, bacteria,  fungi, and humid acid? Thanks guys, Huxley.

Honestly, I cannot think of a good reason NOT too.

It is only a guess unless you test, is a mantra on almost anything. Would you keep going to a Dr who thinks you have Lyme Disease and wants to treat you for that without testing first? It would be pretty arrogant of that Dr to think she KNEW what was going on with you, and knew how to combat it, without first finding out via a test. It is the same with soil testing.

Even if you do the same repeated method on every acre, it is not going to result in the same results, therefore you have to test your soil to see how effective your method is for that area of the farm.

And the opposite is true too. Testing does not just tell you what you are lacking, it also tells you what you are overabundant on, and where you are doing fine. Is it a perfect method? No, but from repeated testing you see trends, and can remediate with applications, certain plantings, and occasionally a pat on your own back seeing that you are doing well.

I test A LOT.

I have three samples going out today if that tells anyone anything, but all year I am having samples sent out every other week or so.

One of the reasons for that is I test for mineralization on my farm, and while this may seem odd, I test soil for minerals I am not even trying to find! This seems odd, but is really rather an effective method. They are called "indicator minerals", and because they are often found in conjunction with other minerals, I can do cheaper, more numerous soil tests to find the indicator minerals, then I could if I was going for the targeted minerals.

Here is an example. I have Palladium here, but to test for palladium is a $60 single test, yet I can do numerous standard soil tests for the same money. Those tests will not show the platinum group metals, but since copper-zinc is almost always associated with palladium, when test results come back high in copper-zinc, then I can narrow my search for palladium to those areas. I will scour that particular area, and when I find something promising, then I will pull the trigger on that single $60 test and confirm or deny palladium is present.

How else can you determine what you are looking for when it is something that cannot be seen? You have to test!

Every one should know what their soil base line is when they begin gardening, farming or just putting in a lawn.
If you don't know what you have to start with, how do you expect to fill in the blanks so you are growing great soil?

I have posted up the what and how of soil testing soil testing and I do think that it should be done, especially when you first get on a piece of land.
I also like to test in the fall of every year, just the garden beds (I treat the whole of my acreage and base the amending on what the garden beds tell me is needed).

Redhawk

I like testing. I often wish that there was a computerised suite of tools that would allow us to do complete soil analyses at home, or even on a peripheral attached to our smartphones.

The more information we gather, the more we can know, and the more we can improve our decision-making processes.

I would look for trends over time, and perhaps delay testing in areas that show steady, positive trends until there is a problem. If time and money were not factors, I would love to have near-constant feedback fed into a spreadsheet and graphed for me, and maybe even imaged on a topographical readout.

But failing that, if I were only able to spot-test to diagnose problems, I would make sure I was applying fungal slurry and compost extract over as much soil as possible, as frequently as I could.

-CK

Chris Kott wrote:I like testing. I often wish that there was a computerised suite of tools that would allow us to do complete soil analyses at home, or even on a peripheral attached to our smartphones.

The more information we gather, the more we can know, and the more we can improve our decision-making processes.

I would look for trends over time, and perhaps delay testing in areas that show steady, positive trends until there is a problem. If time and money were not factors, I would love to have near-constant feedback fed into a spreadsheet and graphed for me, and maybe even imaged on a topographical readout.

But failing that, if I were only able to spot-test to diagnose problems, I would make sure I was applying fungal slurry and compost extract over as much soil as possible, as frequently as I could.

-CK

There is technology available to do your own testing but it isn't cheap. I saw a new model of a system designed to do in field testing of soil and/or plant tissue. Results in a matter of minutes. The equipment plus the software to analyze the results clocked in at just about 30K. I would imagine you could replace some of that convenience and cost with a good dose of organic chemistry knowledge (although that has it's own costs of attainment) but ya, when you look at the infrastructure of quality soil testing it's actually a pretty good deal

Never tested, I do test pH myself but don't test anything else, nor do I try to change the pH. (8) Testing is very expensive (3 samples would be $255) I might get a tiny bit larger veg if I did spend many $ on amendments Yeah probably, but would it make money back I seriously doubt it, I would run a test if I seemed to be having an issue with something specific, but I don't so I don't see the point.

At a pH of 8, your plants can not get much access to many of the minerals they need to produce really healthy foods for you.
The best access of minerals for plants occurs at the pH of 6.8 so you would see a marked improvement in flavor and nutrients if you adjusted your soil pH down about 1.0 points.

Bryant RedHawk wrote:At a pH of 8, your plants can not get much access to many of the minerals they need to produce really healthy foods for you.
The best access of minerals for plants occurs at the pH of 6.8 so you would see a marked improvement in flavor and nutrients if you adjusted your soil pH down about 1.0 points.

I see no difference in flavour between here and my old place that was around 7, nutrients I cannot comment on.

Ammonium sulphate is the only available thing to lower soil pH here (it is very rare to have chalk soil in this country) and one hits the N per hectare limit way before you get anywhere near the amount needed to change even my light sand down 1. I might be able to move the pH south a bit or so with that but it would have to be reapplied every year and all I am then really doing is dumping synthetic N onto my soil which is not what I want to do. I think the only real option is to up the organic matter and buffer the effect that way, It will not be possible to change it permanently as we have loose chalk throughout the soil and the soil is underlain by chalk.

To lower pH ....   the traditional method involves sulfur.  I think it would be good to first test to see if your soil has a sulfur deficiency.  It probably doesn't.   One way to lower pH is to increase organic matter.   And extremely high quality home-made compost is one way to that end (never buy compost - that is almost universally industrial waste).   There are lots of other ways to add organic matter - I would probably go for experimenting with what grows fast and huge on this property.  

The next thing is to explore the world of stuff that appreciates a higher pH.   Maybe if you can get the pH down to 7.5 you might be able to grow alfalfa.  

Another thing would be to explore the pH of your subsoil.   If the subsoil pH is much lower, that opens a LOT of doors.

And then there is this huge area of crazy that would involve growing conifers.   They tend to lower the pH quite a bit, but introduce other problems too.  It could be wise to grow the conifers and then cut them out when they have done their job.  (do we have a thread somewhere on how conifers lower pH?  For a while the official word was allelopathy, and later there was suggestion that conifers were calcium pigs)

paul wheaton wrote:Do we have a thread somewhere on how conifers lower pH?  For a while the official word was allelopathy, and later there was suggestion that conifers were calcium pigs.

The best I could find was this one, but it doesn't get into those issues much:

https://permies.com/t/14160/Conifers-acid-loving-fruit-bushes

I'll work up a post for this topic Paul.

paul wheaton wrote:One way to lower pH is to increase organic matter.   And extremely high quality home-made compost is one way to that end (never buy compost - that is almost universally industrial waste).   There are lots of other ways to add organic matter - I would probably go for experimenting with what grows fast and huge on this property.

...

And then there is this huge area of crazy that would involve growing conifers.   They tend to lower the pH quite a bit, but introduce other problems too.  It could be wise to grow the conifers and then cut them out when they have done their job.  (do we have a thread somewhere on how conifers lower pH?  For a while the official word was allelopathy, and later there was suggestion that conifers were calcium pigs)

I have discussed this with my sister, here in alkali Oklahoma, where berry growing is a challenge.  We miss our Yukon River boreal forest blueberries.  But we aren't interested in buying and floofing out sulfur by the sack.  She's more of a soil tester than me and was horrified to discover that most of her soil Phs were at 7.6 or 7.8.  She immediately set to making mass amounts of compost from all the oak leaves on her property, but they aren't as acidic as we both thought they ought to be.  

We have both wondered whether this is one place where growing conifers over there {gestures vaguely} and collecting their detritus (lower branches, dropped cones and needles) and hauling it over here to put in the composting operation isn't an important part of the solution.  We were always taught to avoid using the rich layer of "duff" under the spruces at home for garden mulch because it would further acidify our already-acidic boreal-forest soils.  The trick here is getting conifers to grow at all, but there are a few, like loblolly pine, that will thrive if treated properly.  By separating the conifer "orchard" from the garden spaces, one trades a bit of haulage for a simplification of the planning problem; you don't have to make the conifers "work" with your other growies.  I'm sure that with enough knowledge about questions like allelopathy and nutrient needs, one could slot them right into the rest of one's permaculture design, but in a landscape like this where they are deeply out of place, it might make more sense to avoid expensive decades-long mistakes by giving them their own space.

I think one could theoretically plant copses, or individual conifers, and water with, say, greywater, which is usually acidic. I would make one such location a regular outdoor urinal.

The conifers will adjust the acidity to their own needs, and there will be an area where the duff drops, and probably down-plume, that will experience higher acidity.

This could even be done container-fashion, buried or not, wherein the root zone of the conifer is contained within soil suited to its needs, and the duff slowly acidifies the surrounding soil. This would probably be better for the establishment of the conifer in alkaline soils, but tbe acidification would likely happen much slower than if it was driven by root-zone exudates.

I should like to see experiments in this sphere. Using life to terraform and adjust biological conditions sounds like permacultural futurism to me.

-CK