lundi 11 mars 2019

144- The soil -6- There is strength in unity


A few days ago, the Facebook page "Sols Vivant - Québec" (French page, very recommendable for those who are interested in the reciprocal influences of soil life and agricultural production), published a very interesting article about the scientist Christine Jones and her work on diversity on and in soils.

This article, dated February 18, 2019 and published in the independent newspaper La Junta Tribune-Democrat, State of Colorado, highlights some points about which little is said, but which could be essential for the future of sustainable and productive agriculture, and for the fight against global warming.

Personal picture

Christine Jones explains that water vapor is the main greenhouse gas. She is not the first to talk about it, but curiously, the public debate has focused on CO2, while water vapor is actually much more important.

Then she talks about diversity as a source of vital power for soil and of fertility for crops.
This is something that has never been discussed, but which may give an interesting trail of experimentation and work for all farmers and researchers who, in one way or another, try to avoid or reduce plowing and increase biodiversity on their farms.
We can summarize his message with this sentence
"Our soils today are not deficient in minerals, they are deficient in microbes"

As usual, I publish the article in its entirety. However, here I removed a short part announcing a conference that Christine Jones will be attending a few days later. At the date of publication of this blog post, the conference is over. So I delete this part so that it does not interfere with reading. But you can access it by the link to the original article.

Soil ecologist challenges mainstream thinking on climate change

By Candace Krebs / for Ag Journal

How cropland and pastures are managed is the most effective way to remedy climate change, an approach that isn’t getting the attention it deserves, according to a leading soil ecologist from Australia who speaks around the world on soil health.

“Water that sits on top of the ground will evaporate. Water vapor, caused by water that evaporates because it hasn’t infiltrated, is the greenhouse gas that has increased to the greatest extent since the Industrial Revolution,” said Christine Jones, while speaking at the No Till on the Plains Conference in Wichita in late January.

“It’s a scientific fact that water vapor accounts for 95 percent of the greenhouse effect, whereas at most 3 percent of the carbon dioxide is a result of burning fossil fuels, and carbon dioxide only makes up 0.04 percent of the atmosphere anyway,” she continued. “So how can a trace gas be changing the global climate?”

That’s a crucial detail the mainstream media and much of the general public have largely missed, in her view.

“It’s got nothing to do with if you burn coal or not,” she stated emphatically.

Jones has a doctorate in soil biochemistry and worked in public research and extension before becoming a soil health consultant on the world stage.

She promotes keeping the soil covered at all times with diverse plant communities while dramatically reducing dependence on fungicides, pesticides and artificial fertilizers. The answer to healthy working landscapes is not more inputs, or even more rainfall, she contends, it’s understanding and capitalizing on the benefits of diverse mixtures of plants working together to draw carbon out of the atmosphere and back down into the soil.


The one principle Jones can’t emphasize enough in her talks is the power of diversity.

She calls for more diversity in the human diet — contending that humans need to eat at least 30 different plant foods every week for a properly functioning gut biome — more diversity in livestock diets, citing the work of Fred Provenza, a professor emeritus at Utah State University who has done extensive research on animal consumption patterns and, finally, diverse landscapes that mirror the complexity of the ancient prairie, which once contained upwards of 700 different grass and non-grass species within each small patch of earth.

To explain why plant diversity is so important, she uses a term that might be new to a lot of farmers: “quorum sensing.”

Soil microbes can sense when plant numbers hit a community tipping point, she said while speaking in Wichita.

“A quorum in an organization is that threshold that needs to be present in order to make decisions and conduct business,” she said. “What we now know about microbial populations is that they also have to meet a threshold in order to achieve “density dependent coordinated behavior.” When that happens, they are working together as a super-organism, capable of tolerating drought, or low nutrient soils, or any of those sorts of things.”

She pointed to research done in Germany that showed having diverse plants growing together boosted biomass production more than adding 200 pounds of nitrogen per acre to straight monoculture crops. In other experiments, mixed plant cultures were able to thrive on an inch of water, while strips of monocultures showed severe drought stress.

“What is happening here goes beyond the simple idea of complementarity, wherein each plant is filling a different niche,” she said.

Diverse mixes increase photosynthesis, which in turn leads to more soil carbon deposition, she explained.

“It makes you wonder why we worry so much about weeds,” she quipped.

The benefits of increased biodiversity hold true for both farmland and pasture, she added.

While some individual plants benefit more from diversity than others, the overall impact of complex interdependent networks of roots and soil microbes is what transforms the function of the landscape as a whole. It all comes back to enhancing the capacity to sequester carbon, she said.

Soil carbon, she has long maintained, is essential for plants to take full advantage of nutrients like nitrogen, something that modern agriculture has tended to overlook.

“Our soils today are not deficient in minerals, they are deficient in microbes,” she said.

Sufficient carbon is also necessary for the full expression of a plant’s genetic potential.

“In the plant world, genetic selection can take you a certain way down the track, but if you do something about the health of your soil you can make quantum leaps in a much shorter amount of time,” she said.

Evidence of healthy soil includes a rich, dark color, high organic matter, an aggregated structure and complex networks of filaments colonizing around plant roots, which enable increased absorption of water and nutrients.

“You should never be able to see exposed roots on a plant,” Jones said. “If you can see the roots on the plant they are not communicating properly with the soil.”

All of these qualities indicate increased carbon sequestration at work.

Jones concludes that changes in farming practices over the last century have done more to impact the global climate than is widely acknowledged. But that also means improving farming practices holds vast potential to change the climate for the better.

“The increasing temperature, the increasing aridity, has come about through inappropriate land management,” she said. “We have made huge changes to the landscape by simplifying it, by removing trees and plants, and by moving from diverse plantings to fields that now grow only one thing.”

It would be too simple to reduce the causes of climate change by stigmatizing agriculture. However its role is important.

But, on the one hand, it is necessary to recognize the mistakes of the past, even if they were made without bad intentions, and secondly to emphasize and favor the ability of agriculture to become the main actor in the fight against global warming and the reduction of greenhouse gases.


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