The book The Farm as Ecosystem, written by Jerry Brunetti, features a lifetime of experience and observations woven together into a useful guide and source of information. Through the text, Brunetti seeks to offer the reader a deeper understanding of evaluating your soil, soil fertility management, compost and ocmpost tea, cover cropping systems, the benefits of biodiversity and more!
The excerpt below goes into detail on legumes and their relationships to soil and the bacteria within.
From The Farm as Ecosystem Chapter 4: The Biological Nature of Soil
An Invitation to Become a Legume
Another exciting breakthrough in nitrogen-fixing bacteria originates out of the University of Nottingham’s Center for Crop Nitrogen Fixation. Professor Edward Cocking and colleagues found a specific strain of nitrogen-fixing bacteria in sugar cane that could intracellularly colonize all major crop plants. Remarkably, this development potentially allows all the cells within a plant to x atmospheric nitrogen! This technology, labeled “N-Fix,” is not a genetic modified/bioengineering technology, either. Rather, it is a seed inoculant, enabling plant cells to become nitrogen fixers, a hopeful boon to annual crop production, which uses wasteful and contaminating amounts of nitrogen. Commercialization of this non-GMO breakthrough is expected by 2015–2016.
In the same vein of investigating the “cellular wisdom” that exists among microbes and plants, researchers at the University of Missouri’s Bond Life Sciences Center, under the direction of professor Gary Stacey, discovered that, for reasons yet unclear, non-legumes have not yet made a “pact” with nitrogen-fixing rhizobia bacteria that allow legumes to convert nitrogen gas into plant food that can be used to build proteins. Legumes recognize these bacteria as their allies, rather than as pathogens, by sensing a signal from the bacteria. The legumes then create nodules where the bacteria gather in order to be fed by the plant in exchange for fixing nitrogen out of the soils’ atmosphere for the plants growth. The rhizobia found ways to produce biochemicals that inhibit the plant’s defense responses, so they can be recognized and accepted as bacterial “friends.” Non-legumes, like corn and tomatoes, were also found to receive the rhizobia signal, which in turn inhibited their plant defense mechanisms against the friendly rhizobia but for whatever reason did not initiate the next step of forming nodules to allow the rhizobia to become symbiotic partners with those plants.
The scientific challenge is thus to find ways to get non-legumes to activate mechanisms that will produce nodules that the rhizobia bacteria can inoculate. If the research at the University of Nottingham or University of Missouri bears fruit, it could have enormous implications on reducing the $8 billion spent yearly by farmers on nitrogen and the destructive amounts of nitrogen fertilizer leaching into our waterways and aquifers. In the meantime, we are blessed with the miracle of nitrogen fixation by the rhizobia with legumes and nitrogen fixation by the actinomycetes bacteria and the blue-green algae with non-legumes and legumes.
Only recently has it been discovered that there are perhaps twice as many archaea species as eubacteria species that are capable of oxidizing nitrogen. Only about 280 species of archaea have been described, yet in upland soils they are estimated to make up 10 percent of the microbial biomass. Like bacteria, archaea are known as prokaryotes, meaning their cells lack a nucleus surrounded by a membrane. Curiously, the genetic construction of archaea is more similar to that of plants and humans than to other bacteria.
Bacteria populations skyrocket in the rhizosphere compared to elsewhere in the soil, to the tune of ten to several hundred times as much. Two types of bacteria inhabit soils. Heterotrophic bacteria utilize organic substances in the soil for their sustenance and transform these organic compounds into plant nutrients. Autotrophic bacteria have the ability to synthesize their own organic compounds from carbon dioxide as well as transform inorganic substances and mineral elements into plant-available nutrients. Bacteria can also be categorized by their shape—bacillus (rod-shaped), spiral, and coccus (spherical)— and whether they are aerobes, which live in free-oxygen environments, or anaerobes, which live in environments absent of free oxygen. There are also facultative aerobes and facultative anaerobes, meaning that they can inhabit both environments, but the facultative anaerobes prefer oxygen-absent environments, and the facultative aerobes prefer oxygen-rich environments.
Bacteria are primary decomposers, but fungi are more significant in that regard. Bacteria use enzymes to fracture bonds that hold organic complexes together. Some bacteria, for example, are able to decompose the most common carbon raw material on our planet, cellulose, by producing enzymes like cellulase. This is an important relationship in creating soil humus. Since bacteria are able to ingest what they decompose, they create non-leachable plant nutrients that are locked up in their bodies until they either die or are eaten by predators like protozoa and nematodes.
Actinomycetes are bacteria that resemble fungi because they produce spores and grow laments. They are the creators of that great earthy garden soil smell, and actinomycetes have been a lucrative resource to the pharmaceutical industry as a source of antibiotics such as neomycin, tretracycline, actinomycin, and candicidin. One of the more popular antibiotics produced by this organism is streptomycin, the first antibiotic proven to cure tuberculosis, discovered in 1943 by soil scientist Albert Schatz, PhD (1920–2005).
Schatz’s forward thinking about soil formation was associated with the principles of chelation. In fact, he authored a text in 1954 titled Chelation (Sequestration) as a Biological Weathering Factor in Pedogenesis and another on the same subject in 1963, titled The Importance of Metal-Binding Phenomena in the Chemistry and Microbiology of the Soil.
Actinomycetes are also nitrogen-fixers, able to extract nitrogen gas (N2) and convert it to ammonium (NH4) by associating with non-legume plants, invading their root hairs, and forming knobby larger nodules than rhizobia do with legumes. The rhizobia, blue-green algae, and actinomycetes collectively x about 140 million metric tons of nitrogen each year, twice the amount of nitrogen fertilizer manufactured by the plant food industry.
Algae are often thought of as waterborne creatures found in swamps, ponds, streams, and rivers, but they have actually been found to be some of the hardiest terrestrial occupants of any other microbial form. Algae may be plants (e.g., kelp) or protists (e.g., bacteria, like cyanobacteria), and all utilize sunlight to photosynthesize sugars and give o carbon dioxide to form that mild corrosive called carbonic acid that can “eat” rocks. The blue-green algae (cyanobacteria) are also capable of fixing nitrogen.
In the top several inches of soil, where there is sunlight, algae can be found in high numbers—as many as 100 million per gram—and can consequently generate quite a bit of organic matter to soils. According to Nardi, in some Arizona soils, algae annually contribute 6 tons of organic matter to the top 3 inches of each acre.
Algae are also found in extreme climatic conditions, such as deserts, and when they are dormant they can survive temperatures of boiling (212°F/100°C) as well as intense cold (-320°F/-195°C). Algae have evolved to form partnerships with other organisms such as fungi, mosses, and bacteria. In desert environments, these partnerships create what’s known as a microbiotic or cryptobiotic crust, where mutualistic collaborations of algae or cyanobacteria and their fungal/liverwort/moss partners protect these fragile and/or semi-arid lands with a glue-like covering that conserves moisture, xes nitrogen, adds organic matter, prevents wind and water erosion, and conserves and recycles nutrients. These crusts can be irreparably destroyed, however, with off-road vehicles and trampling by hooves and feet.
Many years ago, I read the autobiographical account of the mystic G. I. Gurdjie, called Meetings with Remarkable Men, a report of Gurdjie ’s travels to isolated regions of Central Asia and the Middle East. His expedition found that they could keep their pack animals fed while traveling through a vast span of desert without vegetation by experimenting beforehand with two camels, two yaks, two horses, two mules, two donkeys, ten sheep, ten goats, ten dogs, and ten cats. e food created and tested with these species was the following recipe: seven and a half parts sand, two parts ground mu on and a half part salt. Not only was this gruel palatable to these animals, they actually were able to gain weight! Of course, Gurdjie and his crew knew that the nutrition in the sand was some form of “organic substance.” It is my belief that this organic substance was the cryptobiotic or microbiotic crust rich in protein, carbohydrates, fats, vitamins, and minerals.
Lichens are another example of symbiosis between fungi and algae, consisting of blue-green algae (cyanobacteria), golden and brown algae, and the ascomycota fungi. These organisms can survive drought, the hardest of rocks, and subfreezing temperatures. They are primary decomposers of lignin and stone, where the algae produce the photosynthetic carbons and nitrogen fixation to nourish the fungi while the fungi harvest the minerals found in the rock or tree bark. Lichens are extremely abundant, occupying 8 percent of the earth’s land surface, and can live hundreds to thousands of years upon their rock host.
About Jerry Brunetti
JERRY BRUNETTI, 1950-2014, worked as a soil and crop consultant, primarily for livestock farms and ranches, and improved crop quality and livestock performance and health on certified organic farms. In 1979, he founded Agri-Dynamics Inc., and confounded Earthworks in 1990. He spoke widely on the topics of human, animal and farm health.