Soil Minerals and Soil Testing for Organic Gardeners

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Questions & Answers
 

Q:

Hi Michael,

I feel totally overwhelmed with information at this point, but I'm certainly sold on the minerals approach to soil health and therefore to plant, animal and human health as well. I've got a LOT of studying to do to reach a point where I can make reasonably informed decisions as to how to handle my soil.

At this point I am simply amazed at the information on your site. Who are you? And who is Agricola? You have done an amazing job of taking hold, seemingly, of the best available knowledge on soils.

One question keeps occurring to me though, at this early and still quite uninformed stage of my study, and I expect the answer is probably readily available in the information on your site. I just haven't reached that point. I read that much of the available minerals in soil are locked, unavailable to plants or even to microbes I guess. I get the idea that the reason they are unavailable is deficiencies in other minerals that microbes need in order to unlock the frozen minerals. And I understand further that in general soil tests can only 'see' those minerals that are not locked.

My question is, if soil tests cannot see the minerals that are locked, why do we approach correction by adding the minerals that the soil test says are deficient? They might not be deficient, only locked. Why don't we focus on adding the minerals that microbes need in order to unlock the locked minerals? Why don't we do that for two or three years before we put much stock in what the soil test tells us is deficient? Might we not be wasting effort and minerals trying to address tested deficiencies when we could instead promote microbe activity that might unlock the very minerals the soil tests show as deficient?

I'm sure this is an uniformed and probably off-track question. But the way I'm looking at it, an approach to my soil situation might be to simply add either a wide spectrum glacial rock dust (if I can find such), or soluble sea minerals, or both, for two or three years, in an effort to build the microbial life in the soil, before I try to address specific deficiencies. This is based on the assumptions that what the soil most needs is microbe activity to unlock its hidden fertility, and that the fullest possible spectrum of minerals is what will best promote microbe activity. Unfortunately, I'm operating with a low budget, so I must seek the lowest budget approach that will achieve the most for the investment. I'm sure I will not be able to afford the optimum treatment, and will have to be satisfied for now with slower gains in soil health at lower cost.

Any thoughts you have on these things are welcome. Meantime I'll keep studying.

All the Best,

A:

Great questions again.  Thanks for the compliment on the information at the website.  Agricola prefers to remain anonymous.

I found Organic Gardening magazine in the early 1970s when I was in college, and stayed up on it from then on.  In the early 1980s I found out about Territorial Seed Co, and started mixing my own organic fertilizer from the recipe Steve Solomon gave in his seed catalog, trying different mixtures, and I've always experimented with various organic-type soil amendments.  I heard about glacial rock dust in 1990 and used fifty pounds or so of it on my 1000 sq ft garden in the Puget Sound region of Washington, which was a new garden site at that time.  I didn't notice any particular results, so I didn't follow up on it.

In 1999 a friend and fellow gardener gave me a newsletter written by the owner of a garden center in Olympia, WA, not far from where I lived then.  The writer, Gary Kline, had been an organic gardener as long as I had, and like me had kept up on the literature.  In this case he had gone way beyond where I had, and found out about the work of William Albrecht.  His newsletter filled in a lot of missing links for me, in particular the link between nutrition, health, and the soil that food was grown in.  It was a long-lasting Eureka! moment.

I hooked up with Gary Kline, became friends, and we started sharing books and ideas and working on projects together.  After seven years of reading, studying, and experimenting I saw a great need to get this information out to a wider audience. The internet appeared to be essentially devoid of real info on the subject, particularly in a form that the average gardener or farmer could use, so in July 2007 soilminerals.com was launched.

On to your questions:

You wrote: " I read that much of the available minerals in soil are locked, unavailable to plants or even to microbes I guess. I get the idea that the reason they are unavailable is deficiencies in other minerals that microbes need in order to unlock the frozen minerals. And I understand further that in general soil tests can only 'see' those minerals that are not locked.

My question is, if soil tests cannot see the minerals that are locked, why do we approach correction by adding the minerals that the soil test says are deficient? They might not be deficient, only locked. Why don't we focus on adding the minerals that microbes need in order to unlock the locked minerals? Why don't we do that for two or three years before we put much stock in what the soil test tells us is deficient?
"

There are some good points in here, particularly about minerals being in the soil but unavailable unless made available through microbial action.  Dr. Arden Andersen, a physician and PhD Agronomist who I respect greatly, argued in his book Science in Agriculture that several tons per acre of Calcium he had added to a Wisconsin farm did not show up on the standard soil test.  However, it has not been my experience that minerals in the soil do not show up on soil tests.  The various acids and extraction methods that a good lab uses will usually pull out most of what the microbes would find available.  They won't show what's locked up inside a grain of sand or a small pebble, but it would take a very active soil life quite a while to get to that anyway.  Much more common is a soil test that shows good or great reserves of some minerals but the plants are still starving for those very minerals.  Around 1987 was the first time I saw a soil test and recommendations from a county agent that indicated phosphate reserves above 2000 lbs/acre, yet called for the addition of 200 lbs/acre of phosphate fertilizer.  At the time I didn't know what to make of that; now I do.

The three reasons for minerals being in the soil but unavailable are as follows:

1.  Mineral imbalance or deficiency, e.g. there's Calcium there, but it's out of balance with Magnesium, or there's plenty of Calcium and it's balanced with Magnesium but there's a Boron deficit so the soil life and plants can't utilize the Calcium.  Or there's plenty of Zinc but no Copper, or there's too much phosphate and both Copper and Zinc are tied up by that.  The above are all common problems.

2.  The soil life is either non-existent or malnourished or the wrong kind.

3.  The soil energy is out of balance; there's either too high an energy level or too low.  In the case of worn-out soils, such as abused farmland or the continent of Australia, it's usually low energy.  In the case of overfertilized soils, especially those with too high a level of Nitrogen from either chemical or natural sources, or those where Potassium chloride (KCl) is being used,  the energy is just too high and the plants either produce lush vegetation and overproduce low quality crops, or they burn themselves up trying.

It follows that the remedy for these problems is to balance the minerals and provide those that are missing, encourage the existing beneficial soil life to grow and do its job, and address any soil energy problem by cutting back on strong fertilizers if the energy is too high, or increasing energy flow by adding amendments that will kick up the energy level without taking it over the top.

In the Interview With Agricola he likens the soil energy to a battery, and notes that a dead battery and a fully charged one have the same chemicals in them in the same amounts.  The point is that energy flow and movement is what life is all about, and life and our physical creation are largely electrical processes.  Chemical reactions are electrical processes: sugars stack up behind Calcium ions and are transported into living cells, plant or animal, due to an electrical potential difference between the sap or blood and the cell interior.  The negatively charged sugars are attracted to the Calcium ion because it is positively charged.

In a living soil with a full complement of minerals in balance, various living things metabolize the nutrient elements,  go through their lifespan and reproduce, then die and decompose, re-releasing  the nutrients for another life form to use; all energy in motion.  In a soil that has too much water, from rainfall or irrigation, the nutrients can be lost to leaching.  In a soil with too little moisture, the life never gets started strongly enough to metabolize many nutrients in the first place.  We of course want a happy medium, but we are not always able to control the amount of moisture.  We can irrigate dry land if we have the water available, but there's nothing we can do about excessive rainfall.  We can increase the exchange capacity of the soil to give it a better ability to hold onto the minerals that are there, usually by increasing the soil's content of humus and living organisms.  We can also increase the soil's ability to retain water by increasing organic matter or Magnesium, or decrease it  and improve drainage by adding sand or Calcium.

Neither increasing the energy level in the soil, increasing the soil life, optimizing the soil moisture, nor increasing the exchange capacity will do anything to replace  or restore missing minerals.

Your suggestion of letting the soil micro- (and macro-) organisms work to release tied-up nutrients has great merit and is the approach we use daily.  This is why we recommend and use beneficial cultures of both fungi and bacteria.  However, what you appear to be suggesting is to add large amounts of rock dust in order to accomplish this, assuming that the reason the soil organisms aren't making minerals available is because they are lacking certain micronutrients that the rock dust contains.  My question would be, if one doesn't know the mineral composition of their soil, or of the rock dust they are applying, or the soil life that is already there, why would one think rock dust alone would solve the problem?

There is a soil test called the Reams/Lamotte test that is used by some growers and agronomists.  This uses a very weak extraction solution, more like what plants have available themselves, and is meant to give an indication of what soil minerals are readily available to the plants.  I think it would be an excellent experiment to take a soil that was low in soil life activity and had low readings on
the Reams/Lamotte test, inoculate the soil with beneficial organisms, then re-test to see what minerals they had released.  Adding a quantity of rock dust to the soil with or without the added soil life would also give interesting results.  None of these approaches would tell you anything if you didn't know what you started with.

In your earlier letter you mentioned that there were limestone quarries in your area, so it might be assumed that your soil has a good supply of Calcium and possibly Magnesium.  On the other hand, I have read that much of southern Indiana is severely Magnesium deficient.  Magnesium deficiency makes Iron unavailable.  Depending on just where you are in the state, you may have high Calcium with low Magnesium, high Magnesium with low Calcium, or a deficiency of both.  Due to the rather high rainfall, much of Indiana is severely deficient in Sulfur, as are most soils everywhere.  Agricultural Sulfur (90% S) is cheap and readily available, as is gypsum, Calcium sulfate. Agricultural soils need at least 100 ppm Sulfur, and most soils require more than a ton of Calcium per acre. You will not find significant quantities of them in glacial rock dust, and if they are what your soil needs glacial rock dust is not going to solve many problems.  One cannot grow high-quality crops unless the soil's cation exchange capacity is saturated to at least 60% with Calcium, period.  What is your soil's CEC?

If one starts adding quantities of an amendment of unknown composition to a soil of unknown composition one is purely hoping to get lucky, and even if one does get lucky, one won't know why.  Apologies if I'm being a bit blunt here, but  soilminerals.com is based on cutting-edge science, not on luck.  There are already dozens of  websites telling one to add this or that and expect miracles; that's not science and in our experience simply isn't true across a broad spectrum of soils. 

One is unlikely to hurt anything by adding, say, 400-800 lbs per acre of glacial rock dust.  It will almost certainly help most soils; even if the rock dust doesn't contain the minerals your soil needs, the sharp edges of freshly ground rock will boost conductivity and soil energy.  It's my considered opinion that those sharp edges are more responsible for the results that people have reported from using glacial rock dust than any minerals it may contain.  The sharp edges are also easier for the various soil acids and enzymes to attack.  In the ten thousand years since the glaciers retreated from Indiana, the sharp edges they left behind have mostly eroded away.  In places that haven't known glaciers for a few million years, especially those with high rainfall, the sharp edges are long gone as well.

If one is looking for trace mineral sources one is better off using a source whose trace mineral content has been analyzed.  Sea salt is one example of that, or a rock powder whose mineral analysis is known, such as Jersey Greensand, Gaia Green rock dust, Azomite etc.   Perhaps there is a source close to you that has had their rock analyzed.

It's worth noting here that a standard "complete" soil test only measures the amounts of 11 or 12 minerals which are known to be essential.  Many other minerals are known to be essential for optimum health, but no soil lab measures all of them.  Some labs offer additional tests for minerals such as Molybdenum, Cobalt, or Selenium, but each additional mineral they test for usually costs as much as or more than the basic test costs.  All we generally require at soilminerals.com is the basic "complete" soil test for these twelve along with CEC, pH, and organic matter content.  If the test shows that the minor nutrients such as Copper, Zinc, or Boron are deficient, it's safe to assume that other minor and trace elements are lacking too and we will recommend a good dose of a known trace mineral source such as sea solids, kelp, or one of the rock powders mentioned above.

Another point you raised was:  " I must seek the lowest budget approach that will achieve the most for the investment. I'm sure I will not be able to afford the optimum treatment, and will have to be satisfied for now with slower gains in soil health at lower cost ."

I understand this well.  In general, agriculture is not a get-rich-quick proposition, and I encounter few people willing to throw unlimited money into improving their soil, even if it's only a few hundred square feet of kitchen garden.  The approach I recommend is this:

1.  Find out what your soil needs, and/or whatever it already has too much of.  This means get the soil tested .  I can't overemphasize the importance of knowing where you are starting from.  Even if you don't know enough about the science yet to make fully informed decisions, you will never regret having that baseline information.

2. Find the closest source and the best price for the amendments in the quantities you need or can afford.

3. Depending on the budget and what is needed, decide whether you can approach the ideal on all of your acreage, or whether you are better off fully mineralizing a smaller area and doing the rest as the budget allows.

The Ideal Soil:
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