In one teaspoon of soil, there are millions and millions of microscopic soil critters burrowed within the inner crevices of individual soil sediments. Although forgotten, these teeny tiny entities have shaped our planet and have made the earth a hospital place for all living organisms. One of the many ways in which microbes enable life on this planet is through the recycling of key nutrients in the soil. Most of the food consumed on this planet is a direct product of microbial activity and without such microbes, earth’s soils would be barren. There are 4 major groups of soil microbes: Bacteria, Fungi, Protists, and Archaea, all of which play monumental roles in maintaining healthy, productive soil.
Bacteria are by far the most abundant and diverse class of microbes and are more important than one may think. Growing up, we have been told repeatedly that bacteria are gross, harmful monsters, but in fact, only some are actually hazardous. Most bacteria are kind of like superheroes; they perform so many important functions that ensure a healthy, hospitable environment. Bacterial functions within soil include, but are not limited to, improved soil structure, recycling of vital nutrients, and water recirculation. Soil bacteria are also known to bind soil particles together through the release of a sticky substance, to form macroaggregates. These small mounds of sticky soil are a measure of soil health, as they prevent the erosion of soil and allow a safe haven for plant germination.
Soil bacteria can be split up into four major functional groups: decomposers, mutualists, pathogens, and lithotrophs, all of which are key players in keeping the soil healthy. You might be confused as to what these names mean and how they differentiate from each other. However, fear not; after reading this blog, you will be a soil microbiologist in your own right.
Decomposers are bacteria that return key nutrients back to the soil by consuming and digesting dead organic materials. Think of decomposers as Earth’s clean-up crew! Without them, the dead matter would continuously pile up and key elements would never be returned to the soil. Plants are heavily dependent on decomposer activity because without plants there is no oxygen and without oxygen, there is no LIFE! Actinomyces is one of the most common decomposer bacteria on this planet; in fact, they are the ones responsible for that “earthy” smell commonly associated with soil. They are long and tough little guys as they are able to digest extremely strong molecules like cellulose and chitin.
Within the massive category that is mutualistic bacteria, nitrogen-fixing bacteria in soil are the most important mutualists in the soil environment. But before we get into all of that let’s first get into what is a mutualist. A mutualist is an organism that lives within a host or alongside another organism and each involved party has a net positive effect on the other. A great example of mutualism seen within the animal kingdom is the symbiotic relationship between the clownfish and the sea anemone. The sea anemone provides a fortified home for the little fish while the clownfish supplies it with fresh organic matter and nips at any intruder. When it comes to soil, mutualistic soil bacteria work inside the plant root cell to convert atmospheric nitrogen into a form that can be taken up by plant species. In exchange for these important nitrates, the plant will then feed the bacteria sugars which it depends upon for food. As such, nitrogen compounds are a key ingredient in plant growth and survival.
Both decomposers and nitrogen-fixing mutualists use carbon compounds to generate energy and power their respective activities. Lithotrophs, on the other hand, use other elements such as nitrogen and sulfur to create energy. And finally, pathogenic bacteria are disease-inducing microbes that may infect either plants or animal populations. Healthy soil must have an abundance of all four groups of these bacteria because it makes them compete for resources and inhibits the domination of any one type. The “less is more” mentality does not apply here; whenever it comes to the soil microbiome, the more the merrier.
So why is all of this information important?
Well, understanding the vibrant community and underlying mechanisms that make up the soil microbiome gives us a better insight as to what constitutes healthy soil and how that can affect global food production. Over the last 100 years, the human population has grown at unprecedented rates, and with a growing population, there is a proportional increase in demand for agricultural products. In order to keep up with this overwhelming demand for agricultural commodities, grasslands and forests have been converted to pastures and farmlands. This transition in itself completely alters the soil microbiome, killing many of our tiny superheroes that keep the critical balance between nutrients, plant life, and soil.
Moreover, agricultural practices such as tilling, monocropping, and excess use of either fertilizer or pesticides completely shift the soil chemistry, wreaking havoc among the bacteria within the soil. Like us humans, bacteria also have very specific parameters that need to be respected in order for them to live. And with the complete invasion of their space, these parameters are altered, causing bacteria populations to plummet. Alongside antiquated agricultural practices, climate change is also contributing to the ongoing soil crisis. With the increase of torrential rains and unpredictable weather patterns, soil erosion is a pressing issue greatly compromising the future of millions of people.
At the moment, over half of the earth’s topsoil is degraded, and desertification is on the rise. Now more than ever, we need to be proactive about maintaining the condition and overall quality of our soils; otherwise, we will not be able to sustain the ever-growing human population for generations to come. As daunting as the current state of affairs might seem, there is an increasing number of pioneering farmers and agriculture engineers that are actively working on new farming strategies that are more sustainable and help soil bacteria to do their job. Some of these strategies are actually quite simple, like consistently rotating crops or planting cover so that soils are not exposed to harmful elements, or even reducing tillage of the soil. Another way farmers are protecting soil biodiversity is through the use of a range of different mechanical or biological controls on pests instead of harmful pesticides. Organic farming is gaining traction, having an increase of sales of 31% between the years of 2019 and 2020, and is only projected to increase as consumers become more aware of the environmental damage associated with food production. Sustainable agriculture is extremely promising but will only make a difference if the general public takes interest and supports their product. Although bacteria are superheroes in every sense of the word, they do still need a loyal fan base to support their cause. What you can do as a consumer is to take a genuine interest in the sourcing of your food and only support farming techniques that follow the principles of sustainable agriculture.
References
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Hoorman, J.J., Sa, J.C.M., and Reeder, R.C. 2011. The Biology of Soil Compaction (Revised & Updated), Journal of No-till Agriculture, Volume 9, No. 2, pg. 583-587.
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