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.