carbon dioxide Archives

Do you want high oxygen content air? Increase carbon dioxide.

Plants photosnythesize better with an abundance of CO2. Animals thrive with abundant levels of oxygen. The time periods in earth’s history when we had the largest plants, the largest animals, and the highest concentrations of CO2 and oxygen all coincide. It is intersting to imagine how the world might have been different then. It was certainly was very different than our world today, and as the levels of these gasses change in our atmosphere, we should expect plants to grow differently over time.

From the Regenerative Agriculture Podcast with Jerry Hatfield:

John: Jerry, when you spoke about growing in grow chambers, you mentioned that you saw an increase in oxygen content, as well as CO₂. This is something worth elaborating on, because I’ve observed the same thing in the field when we have plants that are photosynthesizing well.

Many people have this idea that there is a conflict between CO₂ concentrations and oxygen concentrations. And I don’t see it that way at all. When we have higher CO₂—specifically when we have higher CO₂ being released from the soil—and when we have good photosynthesis, we get higher oxygen content in the air.

Jerry: That’s correct. And that’s counter to our thought process. You only see that when you start measuring both things simultaneously. I’ve been looking at the literature on the number of papers that actually measure oxygen content within the soil—even the CO₂ content within the soil. It’s really pretty sparse.

It’s not a trade-off between oxygen and CO₂. A good biological system generates more CO₂ because the soil has more pores and more structure to allow gas exchange to occur. That keeps our oxygen content high, which then promotes more biological activity, which generates more CO₂.

Mining the sky, not the soil

Plants are mining the sky, not the soil. Plants are greater than 90% carbon, hydrogen, oxygen and nitrogen, all contributed from the air and water, not the soil.

Here is an excerpt from Charles Walters:

Jan Baptista van Helmont, a 17th century Flemish physician, started getting a handle on exactly what happens when he performed his now famous tree experiment. He simply wanted to know how soil matter was being displaced when plant life grew. No one could measure such a proposition in a field, or in a forest. So van Helmont planted a willow tree in a large earthen tub. The little sprig weighed in at 5 pounds. Soil used in the experiment scaled in at an even 200 pounds. The tub was then covered so that only a small hole for the tree trunk and one for watering remained.

Five years later the tree was not only larger, it now weighed 164 pounds. Obviously, reasoned van Helmont, if the willow tree picked up the difference between 5 pounds and 164 pounds, then the soil remaining in the tub should weigh only 41 pounds, potting material having been reduced to oven dry soil for the post growth weighin. The results proved van Helmont hopelessly wrong. After contributing to the tree’s growth for five years, the 200 pounds of soil had lost only 2 ounces. Van Helmont pondered the problem in deep consternation. Could it be that all this growth came from the water he had given the tubbed tree all these years? Surely this was the answer.1

We have learned a lot in the decades since this experiment.

And we have also forgotten.

The soil lost only 2 ounces out of 200 pounds, while the plant gained 164 pounds.

At the end of the growing period, how much of the 200 pounds of soil do you suppose was organic matter? How much might there have been at the beginning?

Of the 164 pounds of plant biomass, how much do you suppose was mineral content? How much had the plant extracted that was no longer present?

We know that well-managed crops contribute more organic material to the soil than they remove, even when 100% of the above-ground biomass is removed from the field. Healthy soil and crop systems are always gaining carbon, and building organic matter. Mismanaged crops deplete soil organic matter.

What remains to be better defined is the mineral contribution. Experiential evidence suggests that when crops are healthy, the level of soil available minerals constantly increases as well, tapping into the soil mineral matrix of reserves. How many centuries can that be maintained, and what depth of soil profile should we calculate to answer that question?

Walters, C. Eco-farm: An Acres USA Primer. (Acres USA, 2003).