…The Soil Biology Primer represents a new era in our agency’s soil science contributions to natural resource conservation. In the past we have focused primarily on the chemical and physical properties of soil . This publication highlights another integral component of soil , its biological features. The Primer explains the importance of biological functions for productive and healthy agricultural systems , range lands, and forest lands.
The Soil Biology Primer is intended for farmers, ranchers, agricultural profes sionals, resource specialists , students, teachers, and NRCS conservationists, specialists , and soil scientists as a reference for enhanced understanding of the critical functions performed by soil life. I hope you enjoy reading about the fascinating diversity of soil life under our feet and gain a deeper appreciation of the intrinsic value of soil organisms to sustainable civilizations . Protecting our Nation’s soil for future generations is of greatest importance.
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Soil. It’s our greatest treasure.
It can take hundreds of years and many natural processes to make even a centimetre of soil. The mechanical and chemical weathering of rock makes up around half of any soil’s composition, with around 5% supplied by organic material, and the rest made up by air and water.
Put another way, soil is a complicated mix of both the non-organic, abiotic components- minerals, water and air, and the organic biotic components- bacteria, archaea, fungi, plants and invertebrates that live and die within it.
In addition, and bound together with any basic discussion about soil, is the reality of a living soil, the soil food web and soil biodiversity. Soil is a complex, sustainable and dynamic ecosystem, sustained through the complicated interaction of countless soil fauna like worms, woodlice, springtails, nematodes and mites, together with fungi and bacteria.
“Despite all our achievements, we owe our existence to a six-inch layer of topsoil and the fact that it rains.”
However, within a few generations, we have seen the world’s soils rapidly and increasingly degrade, losing nutrients, carbon and fertility, turning saline or actually blowing away. Crops are losing yield and not responding to NPK fertilisers. Fields and farms are being abandoned across much of the world, forcing even more poverty, suffering and human migration. This degrading is mostly human-driven, due to bad farming practices, pollution, acidification, compaction, deforestation and climate change across the world. It’s a sobering and worrying time. Soil biodiversity is dying, with soil fauna like springtails and soil mites reducing to almost zero. Worms are disappearing, fungal activity ceasing.
Soil scientists and farmers are finally being listened to. People are learning and gaining more knowledge and understanding. Research is now well funded and positive changes are being discussed at a governmental level and implemented on a regional and local level. Sustaining, improving and increasing soils is a lengthy and time consuming process, but no dig, microbe compost making and regenerative agriculture are showing great results. Feeding the soil rather than the plant has become a well known mantra amongst gardeners and organic growers. The ship may be sinking, but all is not lost.
Whoever you are and whoever you will become, tread lightly on the earth.”
There is an internet of nature that we are just beginning to understand. It is absolutely amazing and we are just beginning to understand and be able to measure. Together the soil food web and the trees work harmoniously. Here is a video which explains it very well, simply!
Soil Microbiology: A Primer
by Vern Grubinger
|Although it may not be obvious, healthy soils are chock-full of living organisms. Some are visible to the naked eye, like earthworms, beetles, mites and springtails, but the majority of soil-dwellers are very, very small. They’re also very, very important to soil fertility.
Just a few grams of soil, less than a teaspoonful, may contain hundreds of millions to billions of microbes. Not only is the total number of microorganisms in fertile soil quite high, but together, they weigh a lot, too. Soil microbial biomass can range from several hundred to thousands of pounds per acre.
By far, the most numerous microbes in soil are bacteria, which have just one cell. Also abundant are fungi, which produce long, slender strings of cells called filaments, or hyphae. The actinomycetes are in-between these two organisms. They are advanced bacteria that can form branches like fungi. It’s the actinomycetes that give soil its characteristic earthy smell. Fungi and actinomycetes are good at starting the decomposition of organic residues, working on materials that are tough to break down. Bacteria finish the job by eating the more digestible ingredients.
Many other microbes can be found in smaller numbers in soil, including algae, cyanobacteria (often called blue-green algae), and protozoa (one-celled organisms that decompose organic materials and also consume bacteria). Nematodes are microscopic roundworms; some of these are beneficial and some are plant parasites.
The soil zone located immediately around active roots is called the rhizosphere. This is an area of high microbial activity. Materials released from roots, called exudates, create a food-rich environment for the growth of microorganisms. Rhizosphere microorganisms in turn help plants by fixing nitrogen from the soil air, dissolving soil minerals and decomposing organic matter, all of which allow roots to obtain essential nutrients.
Some microbes have a specialized role in the rhizosphere. Rhizobia bacteria associate with the roots of legumes to form nodules. This symbiotic relationship provides the bacteria with a source of carbon in exchange for making nitrogen available to the plant. Farmers are familiar with this process, and often encourage it by inoculating legume seeds with a commercial preparation of the Rhizobium species that is suited to the crop species they are planting.
A special kind of fungus called mycorrhizae also associates with plants. By colonizing large areas of roots and reaching out into the soil, mycorrhizae aid in transfer of soil nutrients and water into the plant. This is especially important in situations where nutrient availability or moisture is limited.
Microbes have a lot to do with maintaining good soil structure, which promotes infiltration and drainage of water, soil aeration, and vigorous root growth and exploration. Gummy substances produced by soil microbes (complex sugars and mucilages) help cement soil particles together into aggregates, which contribute to soil structure. This cement also makes aggregates less likely to crumble when exposed to water. Fungal hyphae further stabilize soil structure as their threadlike structures spread through the soil, surrounding particles and aggregates like a hairnet.
The proportion of the different kinds of organisms present in your soil depends on conditions such as available moisture, aeration, organic matter levels and the type of plants present. Chemical conditions such as acidity and alkalinity will greatly affect soil organism populations. For example, fungi often prefer acidic soils, while actinomycetes thrive in more alkaline conditions.
In order to encourage microbial activity on the farm, soil has to be managed to create a favorable environment for both crops and microbes. This can be done by timely and appropriate tillage that avoids compaction; irrigation and drainage practices that keep the soil moist but not waterlogged, liming to maintain a near-neutral pH, and frequent addition of organic (carbon-containing) residues to provide energy for the microbes.
In general, the abundance of microbes in soil is proportional to the organic matter content. Soils that have large amounts of organic residues regularly added to them tend to support a larger microbial population. However, there is usually an explosion in microbial numbers after the addition of available carbon ‘fuel’, followed by a population crash as that fuel is consumed. Some of the fuel is incorporated into microbial cells and some is given off as carbon dioxide. Later, the microbial cells become food for other microbes and then they, too, are decomposed through microbial activities. So eventually, microbial activity returns to a low level unless more residues are added. The good news is that the microbes are always there, ready to leap into service when environmental conditions are suitable and there’s a source of energy.
For more information on soil microbes, soil management and soil fertility, refer to “Building Soils for Better Crops,” by Fred Magdoff and Harold van Es, available from the Sustainable Agriculture Research and Education (SARE) Program at: www.sare.org/Learning-Center/Books/Building-Soils-for-Better-Crops-3rd-Edition.
Microbes sustain life on earth and they have relationships we are just beginning to understand leading us to discover these smallest of small critters and animals are the basis of all life.
The floriculture of microbes is called the soil microbiome and it is very similar to our humanbiome and definitely intricately connected. Unseen (with our eyes) microbes have a collective mass greater than all the animals on the planet. In the human, there are more microbes then human cells.
We are here because of the microbes and we live in their world!
Microbes (also called microorganisms) are literally everywhere. They grow and reproduce in and on your body, and on rocks, within plant roots and on their leaves, in wetlands, oceans and fresh waterways. And, microbes are in soil. There are more microbes in a teaspoon of soil than there are people on the earth. There are more microbes in your gut than human cells in your body. Soils contain about 8 to 15 tons of bacteria, fungi, protozoa, nematodes, earthworms, and arthropods.
Therein likes the difference to soil and dirt. There is a big difference. The Father of Soil Science, Hans Jenny, defined the 3 components of soil. The first is mineral (texture) which is the sand, silt and clay. Organisms are the second component. And, the third is the organic matter (OM). Without the microbes or the OM, it is simply dirt and void of life.
In the soil, the microbes decompose and recycle; keep us healthy, make the oxygen we breathe, fix nitrogen, control pollution, are a source of renewable fuel. They literally feed the world! Without them, there is no food! And, without these microbes healthy we may have a plant we can eat force with “ides” and “izers” but it contains no nutrients. It is like the difference between a tablet of processes vitamin C and a sprig of parsley from good soils.
It is a web of precious live science has neglected for too long Soil microbes throught recycling and decompossition release chemicals (such as carbon, nitrogen, and phosphorus) that can be used to build new healthy plants (and animals). So, the flower or a vegetable will eventually become part of another living thing chemically. So the next time you see cut flowers decay or a garden vegetable rot, remember, you’re really seeing microbes at work.
Our understandings about these microbes is now giving us solid information about how to provide the environment and the biology to ensure the good microbes thrive. Science is now discovering the microbe world in research that “…just like the human gut or plant roots, the hyphae of AM fungi have their own unique microbiomes,” Scientist at the Maria Harrison, Scientist at the Boyce Thompson Institute (BTI) “https://www.eurekalert.org/pub_releases/2021-04/bti-fcm040221.php?fbclid=IwAR28ooKSVt8nVrEltXp0d0vz2Z6XSv-SpaBb2Bw7RaiMezc1UUBg1yMkDQM
Everything has a symbiotic relationship. For example, all living things require nitrogen for building DNA, RNA, and protein molecules. We knew nitrogen is abundant in the atmosphere but only a few species of microbes can use it in this form. All other organisms depend on certain bacteria that produces enzymes that convert or “fix” gaseous nitrogen (N2) into a form other organisms can use (such as ammonium (NH4+) or nitrate (NO3-)). Nitrogen-fixing bacteria depend on plants for food therefore forming a symbiotic (or mutually beneficial) relationship. Animals (including us humans) in turn acquire nitrogen by eating plants and plant-eaters.
Other metabolically talented microbes can metabolize metals, acids, salt, methane, or even radioactive wastes. We are discovering a microbe for every pollutant. Thus microbes can treat sewage, clean abandoned mines, and degrade a variety of industrial chemicals.
We are just beginning to understand and appreciate this minute world at greater depths. Maybe it is just in time because we have spent years destroying them and following practices (both chemical and organic) that have harmed their cycle of life. Soil biology is the mediator of life on Earth. It is the function of the biological systems acting as the “gut” of plants.
When we look into the soil with our microscopes we want to see bacteria, fungi, yeasts, protozoa and nematodes. They act as microbes in the gut biome to solubilize, sequester and digest the minerals from the sand, silt, clay, rocks, pebbles and crop residues into plant available nutrition. This nutrition translates for us humans as amazing “taste” that is satisfying. This is referred to as nutrient cycling and in symbiosis with plants, they (the microbes) are critical for carbon cycling also.
We all, farmers and gardeners alike, are realizing this the soil biological system that literally is the “gut” of our environment. Big money AG and the wrath of herbicides, insecticides, fungicides, soluble fertilizers and tillage have left soils void of some of these microscopic soil managers. They are out of balance. Without them, we are left to chemistry that may superficially be a short fix but it is harming the critters. As our understanding of many of the “-cides” used in agriculture increased, it is clear how devastating these can be to the microbes. We need to eliminate or at the very least, use wisely, all forms of insecticides and fungicides so as to not compromise the biodiversity. We need to rebuild the biodiversity.
One of the fundamental theories from soil consultants is that not all soil testing is created equal. Simplistic N-P-K and pH tests are fine for determining fertility needs, but worthless when it comes to rebuilding soils. To rebuild you have to understand the microbiology.
It is important that we remember to view soil as a habitat and an ecosystem, and to shift our mindset from feeding plants to feeding the soil, which will in turn feed the plants and support them in many other ways. Microorganisms are “everything” and is relevant to everybody. The proof is around us everywhere. Microbes actually do everything.
Soil microbes are the simpliest of creatures that created our environment we live in. In our soil microscope and compost making we are particularly interested in bacteria, fungi, protozoa, nematodes and soil microaggregates (held together by the microorganism glue).
There are microbes in us, on us and acting upon everything around us. If we don’t understand them and stop harming them, there will be no nutrition from our plants and we will left with only “dirt”, barren land, anaerobic conditions and life will cease. We have to look at this differently. We have help the microbes thrive. We all need to eat and we all need healthy nutrition. Microbes are responsible for creating soils we all desperately need.
Recently, so many insights into how life happens becauses of microbiology. The microbes are the engines of production and understanding their role and helping them flourish translates to true sustainability longterm. As we learn more and more we realize they offer roots to all the solutions we are seeking…at least the most fundamental issue we are face with collectively and that is “health”. It is important now and even more important in the future. Taking care of the soil is taking care of the whole!
I went on a mission to learn the best method for growing a beautiful lawn naturally. I took it back to the historical roots, learned the reasons we are obsessed with it and then saw grass from an ecological standpoint. Grass is an amazing and super beneficial edible and medicinal plant. If there is one plant we should know it’s how to care for grass. All grass can help us improve our soil as a source of nitrogen for compost with all the new growth rich in nutrient and it’s a source of Protozoa and fungi for many holistic soil management methods. Believe it or not the best way to get grass healthy is to make a tea using healthy grass.
All this works with many plants because to get a plant healthy naturally it has to have its support system. The parameters for growing a plant is the plant in many ways.
Like the concept of we need money to make money when we grow we need life to make life. I didn’t just use grass to make my yard grow this well but for those struggling to understand human engineered teas and extracts plant for plant teas can make a big difference. To make a plant to plant fertilizer we can put a plant in a blender, strain and dilute the juice in 5 gallons of fresh water and scoop, drizzle or spray it onto the same plant we blended. Some plants can affect others differently so if you use one plant to fertilize another and get it in the foliage do so with caution using trial and error hesitations. I don’t want to be responsible for someone using a toxic tropical plant on our natives thinking a healthy plant makes a healthy plant. This is only part of the message. D
ifferent plants have and need different microbes. Kale needs actinobacteria but put actinobacteria on tomatoes and you’ll have blight showing in a few days. I want to help but as with many things I’ve learned the standard ecological answer is, “it depends” so look for 2 sides to everything within the biosphere … “that’s life”, as they say.
The Garden map is the mission and vision of Living Ground
I acknowledge the superiority and necessity of “Natural Systems” over the artificial stimulation methods employed by traditional plant care practitioners (both organic and chemical).
I strive to learn more about the soil microbiome, we see the connection to all life and especially human life. We are a part of and not separate.
believe that land suffers from a deficiency of “chemicals” or nutritive value. Thus, it is time to encourage movement away from chemical dependencies.
I can enhance the beneficial natural soil biology that supports plant health.THe Microbiology Approach provides peace of mind for all growers while the landscapes are being cared for in a more environmentally sensitive manner.
I follow, to the best of my ability, nature’s way
I create from the land. I alchemized taste and texture from the plants and desire each product to be a sensation of happiness from soil to plant to kitchen alchemy.