Re: Soil Equilibrium

From: Elaine Ingham (Soilfoodweb@AOL.COM)
Date: Wed Jan 01 2003 - 20:25:58 EST


Hi again Rick -

You pick easy questions, don't you? :-)

> Assuming that a producer were to
apply the recommended levels of P, K,
and lime in a one shot application to
permanent pasture, would it take months,
years, or decades before the soil reached
an equilibrium for these nutrients?

Depends on the health of the soil community to which the material was applied, what time of year it was applied, how much organic matter and humus was present before application, what plant species were desired, and the soil type.

A healthy soil won't need much amendment, so it could be a short as a few weeks before the organisms recover.

A permanent pasture in the process of losing the desirable grass species will require more nutrient amendment. The impact of the chemicals will be longer.

Why is that soil losing the nutrients it used to hold onto? The organisms in the soil were lost.

Why? Could be compaction. Too many animals, consuming too much of the biology. Roots systems harmed by the compaction, and losing depth. Loss of the roots, means loss of food for the beneficial bacteria and fungi. Which means lack of nutrient cycling, lack of ability to hold the nutrients. Plant species will be lost, the pasture loses productivity.

Loss of nutrients is a symptom. You will never solve a problem by addressing the symptom. You have to fix the cause, AND the symptoms. You have to de-compact the soil.

How do you do that? You can't plow a pasture. Well, you can, but then it isn't a pasture.

If you apply tons of chemicals to add back the nutrients in an inorganic form, you will kill more organisms in the soil. But if you add organic matter, or foods for the organisms at the same time, then the results are different. You might be able to re-build.

Have to understand all parts to be able to predict. But I know areas that were in pasture when I was a child, were plowed once, and the field is still in weeds.

I know go-back fields in Colorado where the soil was plowed only a couple times, and maybe those plow events were back in the 1940's. The plant species are still just mostly weeds. Just because you stop plowing does not mean the biology comes back. I did some work with people at Washington State where they thought that areas in conservation reserve (CRP) would be good examples of healthy soils. The organisms data came back so variable, they stopped working with me, because they thought they had proven that the assays we do aren't accurate. Sigh. No, the data were exactly right. Some places had recovered, other places had not.

You'd think graveyards would be fairly healthy, but they are not necessarily. Look at the plant species. Weeds? Not recovered.

There are forests in Oregon that were clear-cut in the 1920's, and they still cannot grow trees in those sites, although the forest in the not-cut surrounding areas are perfectly fine. Dave Perry has a set of example systems where that has happened.

Other forests (a study by Moldenke, for example) where you can still detect differrences in the microarthropods based on the time of year the stands were cut.

How long does it take to get the soil back to healthy conditions? Think about balds and parks in the mountains. They may be hundreds of years old. Think about Canyonlands, in Utah, where Jayne Belnap has studied the effect of limited grazing disturbances back in the 1800's. The change in plant species is still apparent. Arid conditions are much more fragile. Places where rain is more plentiful re-builds the biology faster. Plant communities can recover faster, because the organisms have something to grow on. But they do not always do so. Why? The answer can lie in the biology.

So, the answer is the standard ecological one. It depends.
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And as in the last e-mail, those of you who want to object to something, please don't just fire off a reply. So often what is demonstrated is that you didn't read what I wrote. Read carefully. There are complex points here. Different experiences are useful, we all learn something that way. Although most of the time, when we discuss what seems to be a similar situation, what we discover is that in fact, it is a very different condition. I can't cover all parameters in a short e-mail.

Elaine Ingham
President, Soil Foodweb Inc.
Corvallis, OR
Port Jefferson, NY
Lismore, NSW, Australia
Hilversum, The Netherlands
www.soilfoodweb.com

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