Contrary Science; Cover Crop Mixtures, Monocultures, and Mechanisms

This post from Andrew McGuire of WSU is part of an ongoing scientific discussion about the relative effects of cover cropping and monoculture. This excellent summary of historic and ongoing research helps to bring us up to date on this complex, fascinating, and timely subject.

Excerpt from the article:

Soil diversity not linked to plant diversity

One last contrary finding. Another common belief is that a diverse mixture of plant species will drive greater diversity in the soil than a monoculture. This is often given as a reason to grow cover crop mixtures. Here again, we have a new analysis of the accumulated research investigating this mechanism. Zhou et al. (2020) analyzed 1235 experiments done around the world on the effects of what they call global change factors on soil microbial diversity. These change factors included land use change, such as occurs when a natural ecosystem is converted to agriculture, and nutrient fertilization. From this analysis they make several surprising conclusions.

First, most changes in the number of species (alpha diversity) can be explained by a change in pH. pH! It truly is the master variable in the soil. This is good news, as we can and often do manage soil pH.

Second, as they state it, “Conversion from highly diverse natural ecosystems to homogeneous agricultural monocultures has a positive effect on microbial alpha diversity.”

Read that again, a positive effect. The same goes for conversion to pasture.

What is more surprisingly contrary is that this implies, and the authors state this, that changes in soil microbial diversity (number of species) are NOT linked to changes in plant diversity. I know, heresy, but thus sayeth the science.

This does not mean that the conversion to agriculture is all positive. The microbial biomass is reduced, probably due to the change from perennial to annual plants and the associated decrease in carbon flow to the soil3. Agriculture also changes the structure of the microbial community. What these structural changes mean in the crazily complex soil is a difficult question to answer, but they may all not be beneficial with respect to the soil or the environment. This does, however, remove another purported reason of growing cover crop mixtures.

Read Andrew’s full article here:

Chemolithoautotrophs!

One possible way that subsurface microbes can combat climate change is by capturing carbon and converting it to limestone.

These microbes use chemicals from rock as an energy system to feed themselves far underground, in the absence of sunlight.  In doing so, they can produce organic matter that fuels the growth of other organisms, they can convert CO2 to fuels and other chemicals, and they can enhance the efficiency of solar panels (“photon-to-fuel efficiency”). 

At the Washington State Soil Health Committee, we wonder what relationship these microbes have to topsoil?

What do you think? What do you know?

Fixing Climate Change – Boosting Nature’s Cooling System – Fixing The System

This exciting article from Fixing the System discusses soil as the engine of our planet’s cooling and carbon capture system.

Here’s an excerpt from the article:

“Rich soils exponentially increase the capture of water and carbon
What is powerful about healthy soil, and it really is the central element of the whole sponge discussion, is that now we have 66% of the volume of the matrix which is available for infiltrating and retaining water. That retained water is what can sustain plant growth. Because of these voids, and the increased surface area exposed by them, this healthy soil can vastly increase the availability of nutrients. Now we have the phosphorus, the calcium, and the zinc all exposed for microbial activity.

So the bio-productivity of that soil increases exponentially, simply by creating those voids. The rootability of these soils vastly increases, that is the roots can grow, and penetrate and proliferate. Instead of 6 inches, they can grow down to 6 feet, or 20 feet, so the volume of soil resource that is now available for plant growth, and the drawdown of carbon that we mentioned earlier, is exponentially increased.

Soil formation is the engine of nature’s cooling and carbon capture system
So the whole bio-productivity of these healthy soils, the resilience of those soils, the capacity to infiltrate, to buffer, to extend life vastly increases. This process is what nature did to create the biosystem, to create the hydrology, and in very simple terms, that is all we have to do.

The process is taking sunlight, carbon dioxide and water to produce plants, using photosynthesis to create sugars, and fungi and microorganisms that convert those sugars into stable soil carbon, which is just the carbon based organic detritus or ‘bed springs’. This process is how the Earth ran 95% of its heat dynamics and its natural hydrological cooling.

So, if we have to draw down 20 billion tonnes of carbon, if we have to rebuild this soil-carbon sponge, we simply need to copy nature, and speed up the soil formation process.”

Ancient Soils found in Western Australia

A week or so ago, scientists reported that soils collected in Western Australia contain tiny micrometeorites, compact balls of cosmic dust. When these soils were formed, about 2.7 billion years ago, cosmic debris was penetrating our atmosphere and seeding the ground with cosmic dust which persists in our soils today.

High-resolution microscope view of a tiny iron micrometeorite the size of a grain of sand. Analysis of these particles shows that Earth’s atmosphere used to contain a lot more carbon dioxide 2.7 billion years ago. Image via Andrew Tomkins/ Penn State.

The study of these micrometeorites is revealing the chemistry of Earth’s atmosphere nearly three million years ago and should also reveal the chemistry, and possibly some of the biology, of our ancestral soils.  

These new peer-reviewed findings were published in the journal Proceedings of the National Academy of Sciences on January 21, 2020, with one of the authors, Owen Lehmer, from the University of Washington. As the authors explain:

“Carbon dioxide concentrations have varied widely over the Earth’s 4.54-billion-year history. This new work helps quantify the elements that made up Earth’s atmosphere in the very distant past.

The tiny iron micrometeorites that were studied are no larger than grains of sand. They were discovered in ancient soils – called paleosols – that are about 2.7 billion years old. The soils were collected in the Pilbara region of Western Australia. These scientists believe the micrometeorites fell from space during the Archean eon, when the sun was weaker than today.”

Riverday School Students Study Tardigrades

In January 2020, students at Riverday School in Spokane, WA did a variety of projects around tardigrades. Students created posters, took samples, and visited Gonzaga University to view live tardigrades. The students are supporting the initiative to make tardigrades Washington State’s micro-animal.

Here is a short video of their work on tardigrades. This footage was shot by the students themselves.

Here is the full video as shot and produced by the students.

There are also lots of pictures of the students during their trip to Gonzaga, as well as the teachers involved and the posters the students made.

Washington State High School Students Study Tardigrades

Last week, Lynn Bahrych delivered 30 living tardigrades to the science classes at the Friday Harbor High School on San Juan Island. The tardigrades will be studied and hopefully “cultured” in the classroom as part of a campaign to have the tardigrade designated as Washington State’s “Micro-Animal.”

On November 12, 2019, following the delivery of the tardigrades, Lynn and a volunteer marine biologist and videographer, Dr. Michael Noonan,  joined Sam Garson, the Friday Harbor High School science teacher, to introduce the project to his science class. Mr. Garson had prepared slides for the classroom microscopes, as well as a worksheet  (titled “Behold the Mighty Water Bear”) and video introductions of the tardigrade and the research being done on it now to study evolutionary development (”evo devo”).  

Not much is known for sure about tardigrades, so these students might be able to contribute something new to the field. Tardigrade ecology is in its “infancy,” according to experts. Exciting new ideas may come from the three classrooms across the state participating in this project. In addition to the Friday Harbor High School on San Juan Island, the Riverday School in Spokane, and the Roosevelt Middle School in Olympia are studying the enigmatic “moss piglet” or “water bear.”

For the state designation of the tardigrade, there are three state legislative sponsors at this time; Representative Jeff Morris of District 40, who is the primary sponsor,  Senator Debra Lekanoff also from District 40, and Representative Marcus Riccelli from Spokane.  Once the bill is filed in Olympia, other legislators will be invited to sign on.

This is the education and outreach project for the Soil Health Committee for 2019-2020. The goal is to raise awareness of soil health across the state by focusing on a charismatic animal that lives in soil and, in ways we are only beginning to understand, contributes to soil health.

A few fascinating facts about tardigrades:

  • In 2008, two “super-predator” Tardigrade species were discovered that suppress nematode communities despite being greatly outnumbered by the nematode populations. This may be very good news for producers with nematode issues. That is, unless the tardigrades also eat beneficial critters, which is why more research is needed.
  • In 2015, Japanese scientists found “high expressions of novel tardigrade-unique proteins,“ including one that suppresses radiation damage When inserted in human cultured cells, this unique tardigrade protein suppressed X-ray damage to human cells by 40%.
  • Tardigrades work as a “pioneer species” by inhabiting new developing environments and attracting other invertebrates, including predators looking for food.
  • Tardigrade species have been found in fossils 530 million years old and are often described as the champions of climate change, having survived the last five mass extinctions.