WEDNESDAY, JAN 24, 2023: NOTE TO FILE
Module 3-3
Biodiversity and the soil microbiome
Life on Earth is sustained by a very thin crust of living soil. The fundamental basis of all regenerative forms of agriculture is healthy living soils. Extensive interdisciplinary research blending botany, biology and ecology with microbiology has shown that the symbiotic relationship between plants and microbial life in the soil is crucial to the health of all plant life and the nutritional value of the food we eat. Moreover, healthy living soil is the key to a healthy biosphere, and it forms the basis for all those interconnections that keep the cycles functioning. Healthy living soil contains an abundance of mycorrhizal fungi and bacteria (see Figure 2.2a). The Human Microbiome Project has revealed that 90% of the genetic material on and in our bodies is microbial. We are an ecosystem. Our gut microbiome weights over 2kg and it is responsible for building our immune system, regulating our metabolism and even our moods by sending neurotransmitters through the vagus nerve to affect our brain chemistry. In our digestive tract, microbes digest fibre, manufacture enzymes and vitamins, crowd out pathogenic bacteria, and clean and repair the gut wall. Without them we would die and so would they. Keeping us healthy and alive is in their interest too. Our gut microbiome is the primary interface with the microbial world outside via our food. There are direct interactions between our gut microbiome and the soil microbiome.
The soil microbiome relies on plants to provide carbohydrates for its energy source. Plants create sugars through photosynthesis and some of these, up to 70% in some cases, is exuded into the soil through roots. There it feeds the mycorrhizal fungi and bacteria that in return pass nutrients and water to the plants. In forests, it has been shown, that mycorrhizal fungi carry chemical messages (pheromones) and sugars between trees forming a symbiotic network of communications and nurture. They also produce chemicals that are antiviral and antimicrobial to treat wounds and diseases and can attract and repel other species as necessary. When there are significant numbers of microbial communities present, they take part in what microbiologists call ‘quorum sensing’; they can ‘decide’ to enhance the nutritional content of plants and can even switch plant genes on and off. Naturally, as the plants are feeding the microbes, it is in their interests to keep those plants healthy and functioning. A diverse polyculture of plants above ground ensures a large number of microbial communities below ground.
Watch this short video about the Jena Experiment at the Frederich Schiller University in Germany were field trials over a ten year period showed the conditions necessary for sustaining biodiversity.
The potential for producing large quantities of healthy food for human health and well-being while regenerating ecosystems is vast [organic agriculture with all industrial inputs other than fertilizer and pesticide is less productive per multiple meta-analysis studies not withstanding decades of claims by the Rodale Instute (a meta-data analysis of 362 studies, but another meta-analysis of 205 comparisons found only a 9 percent decrease on average; Nature found a 5 percent gap for some crops down to a 34 percent (76% of conventional or about 80% average) lower organic methods yield "when the conventional and organic systems are most comparable"), so alternative farming is about 80% as productive as compared to straight out no-inputs-spared conventional agriculture that currently "feeds the world"]. But our present agricultural systems are doing the opposite. Artificial fertilisers, agricultural chemicals and continuous tilling and digging for annual crops kills the soil microbiome. Because we mistakenly believe we have to add nutrients to the soil [henced adding nitrogen and other industrial fertilizers at great expense is done only because it is falsely believed to provide an illusory benefit?], we are also killing the microbiome. Soil does not need amendments if we nurture the microbiome. Microbes can produce enough reactive nitrogen for uptake by plant roots, others release minerals from parent material and make them available, even passing them from nutrient rich areas to nutrient poor areas. And it is microbial life that creates soil itself (as opposed to ‘dirt’) using the sugars exuded from roots, breaking down dead matter, creating substances such as glomalin that create that rich, friable, crumbling texture that is the organic carbon sequestered in soil.
Animals also build soil organic carbon by consuming fibres such as cellulose in grass and their dung is food for invertebrates and soil microbes. Cattle dung can support up to 250 species of invertebrates at one or another point in their life cycles, thus adding considerably to maintaining biodiverse ecosystems as well as soil organic carbon and microbial communities.
The soil food web, shown in Figure 2.2b, breaks down organic matter, increasing soil organic carbon and making nutrients available for plants.
Module 3, lesson 4
