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:

Injecting bacteria into rice paddies could reduce methane by over 90%

A newly discovered bacteria shown to reduce greenhouse gas produced by rice fields by up to 93%

Researchers in Denmark and Germany have shown that adding a recently discovered bacteria, called a “cable bacteria,” to rice plantings in their test lab resulted in a 93% reduction in the release of methane gas. Today rice fields worldwide are responsible for over 11% of all methane, a greenhouse gas several times more potent than CO2. The cable bacteria, one centimeter long (which is big for a bacteria), is named for its ability to create an electrical current along its filaments which oxidates the sulfides that cause methane, creating sulfates in deeper soils. This causes a downward migration of sulfates, boosting sulfate density in soils that outcompetes methanogens, the bacteria that cause methane gas.  Aboveground plant growth was not affected by adding cable bacteria in this experiment.

The current practice of adding sulfates (ammonium sulfate or gypsum) to reduce methane causes an unhealthy build-up of sulfates in topsoil. But with bacteria recycling sulfides into sulfates below the surface, this build-up is prevented. The production of methane gas was reduced by 93% in this study. Field trials will follow to test the results on a larger scale.

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?

The Tardigrade nominated as Washington State’s Official Micro-Animal

Tardigrade: Proposed Official State Micro-Animal of Washington

Two Washington State schools are nominating the Tardigrade as Washington State’s Micro-Animal. The science students at the Friday Harbor High School on San Juan Island and the students at Riverday School in Spokane have studied the Tardigrade as part of their science curriculum and found it to be worthy of becoming the Washington State Micro-Animal. The Tardigrade, which means “slow stepper” and is sometimes referred to as the “water bear” or “moss piglet,” is among the most resilient animals alive today, having survived the last five mass extinctions. They are found in fossil records 530 million years old.  A native of Washington State, found in every county and habitat, it lives in mosses, lichens, marine and freshwater sediments, soil, seawater, freshwater, glaciers, hot springs, deserts, and rain forests. They are important ecologically because they eat other micro-organisms, such as crop-destroying nematodes, as well as plant cells, and help to clean both soil and water. Due to its amazing ability to withstand extremes, such as boiling mud pots in Yellowstone, glaciers on mountaintops, the vacuum of space, extreme drought, and radiation, the Tardigrade is being studied for new methods of adapting to climate change, as well as for preventing radiation damage from cancer treatments. Tardigrades may also be the first colonists on the moon since they crash-landed there in August of 2019. According to an international expert on Tardigrades, Lukasz Kaczmarek, they are likely to have survived because “Tardigrades can survive pressures that are comparable to those created when asteroids strike Earth, so a small crash like this is nothing to them.”   This and many other extreme achievements of the Tardigrade make it the perfect Micro-Animal for the Evergreen State.

UPDATE: Washington state high school students attended legislative sessions in Olympia in support of making the tardigrade the state micro-animal.

Below are pictures of the students at the statehouse. Featured in one of the pictures is Representative Alex Ramel.

Before the hearing, Representative Alex Ramel took a few moments to talk to the students that would be testifying.

Earn Income for Enriching Your Soil

This program is available to agricultural producers through 2019 who sign up on the indigoag.com website.


In June of 2019, an international project was launched to pay farmers by the acre of cropland to adopt “regenerative growing practices.” It’s called the “The Terraton Initiative.” 


In the few months since it started, ten million acres of cropland have been enrolled by producers willing to use one or more regenerative practices, for example, cover crops, crop rotation, no-till, reduced pesticide, and fertilizer, or integrated livestock management. Producers receive a minimum of $15 per metric ton of carbon dioxide sequestered in their soils, as measured by remote sensing and breakthroughs in data science. It is now possible to make accurate, efficient, affordable measurements of soil carbon levels by remote sensing methods.  The producers who have enrolled their cropland in this program will not only build healthier soil, which will increase their yield but will be paid a bonus for doing so. 


For more information on this new program, go to indigoag.com

New Findings in Plant Root and Fungal Interaction Help to Resolve the Complexity of Soil Carbon Cycling

The general background of this research is that a major part of the global carbon pool is stored underground, in our boreal forests, in the form of organic matter. It is only now becoming clear how plant roots contribute to the formation of organic matter, especially to the concentration of nitrogen in it. The latest research on soil nitrogen shows that some plant roots promote high concentrations of organic soil nitrogen, thus contributing to for formation of organic matter, where carbon is stored. 

Read the article from Phys.org

North Central Washington Cover Crop Tour October 4th, 2018

Hear from farmers about cover cropping and grazing in dryland wheat. There will also be updates from RMA, NRCS, and WSU on soil health and animal nutrition.

The Field Day will take place on October 4th, 2018. The tour will start at Cavadini Partnership in Bridgeport and end at the Double J ranch in Okanogan. Following the tour, there will be beverages and a BBQ.

Please RSVP by September 22nd. To RSVP, email rachel@okanogancd.org.

 

Washington State Soil Health Project Reports 2017

These are the first reports for the eight new contracts for 2017-2020 and for the continuation in 2017 of the first round of projects, which received additional funding. The results are encouraging and, in some cases, fascinating. By demonstrating positive outcomes, these results will promote better soil practices in our state.

Palouse Rock Lake Conservation District:
A new project to measure and compare moisture retention in cover crop fallow and direct seed fallow.

This study is a home run. By comparing moisture retention every four inches up to 48” in side by side cover crop fallow and direct seed fallow, the study has these results so far:

  1. No net loss of moisture in cover crop fallow as compared to direct seed fallow
  2. Decrease in soil temperature in cover crop fallow, which benefits soil organisms
  3. Suppression of weeds without herbicides
  4. Reduction of soil compaction, which enhances moisture absorption and retention
  5. Reduction in soil erosion
  6. Early signs of possible increase in yield

San Juan Conservation District:
Continuation of biochar project begun in 2016. Following up on the original six-farm test plots, in which biochar was added to soil, the yield will be evaluated in the spring of 2018. In addition to the test plots, biochar kilns were designed and provided to forest landowners on each of the four ferry-served islands. Workshops were offered on each island to demonstrate how to make biochar from forest waste. Online instructions are available for making biochar at home.

Biochar was added as an alternative to the slash burns in the County’s draft Solid Waste Management Plan.

The San Juan CD also starts a new three-year project to introduce no till-direct seed practices to the county, including use of cover crops to improve soil health and limit use of chemicals.

Underwood Conservation District:
Completion of original 2015-2016 project to monitor soil moisture in test plots in an orchard, using a control plot, a plot with compost, and a plot with compost and mulch

Results so far show no significant difference in moisture. We are waiting to hear if there is any difference in productivity (yield). We have questions about the 2017 workshop: how may attended, who were the presenters, and what did they present?

Washington Environmental Council:
Continuation of Nisqually Community Forest project which aims to create a template for sustainable forest practices in Pacific Northwest forests.

  1. The project has linked sustainable forest practices with improvements in both water quality and quantity
  2. DOE’s Clean Water Revolving fund was changed to allow sustainable forest projects including forest land purchases
  3. First certified Carbon Project with 520 acres saved from clear-cutting with Microsoft buying the carbon credits
  4. Set up protocol and step-by-step process for creating and selling carbon credits to offset the cost of land purchases
  5. Demonstrating that by growing trees longer, e., longer harvest rotations, the forest is more resilient and stores more carbon over time; older forests also provide better wildlife habitat

    Whitman Conservation District:
    Experiments with various cover crops in the Palouse to identify those best for fall and for spring and to determine whether pelletized compost adds extra yield or other ecological benefits. This will be evaluated in the spring of 2018.

Washington State University: Soil Health Field Day
Soil Health Field Day in Davenport at the experimental farm. Well attended with dozens of farmers and conservationists. Highlighted soil differences between no-till and conventional test plots.

Washington State University:
First year of three-year study of soil characteristics in irrigated agriculture in Eastern Washington.

  1. 60 soil samples were studied from 30 growers to establish a baseline.
  2. Some of the results were surprising, for example, that the amount of soil fines was inexplicably low in many sites.
  3. Several “exemplary soils” were discovered, which were also surprising. More research will be done to discover the secret of those exemplary soils
  4. This study includes a process of evaluating which soil health measurements are of value, and which are not.