There is a whole ecosystem of life, both microscopic and visible to the naked eye, operating within healthy soil; it is the universe of the underground.
In fact, a teaspoon of good soil contains 1 billion invisible bacteria (of which there are 20,000 to
30,000 different species), several yards of fungal hyphae, thousands of protozoa and a couple dozen nematodes.
If this life is mostly microscopic, small and often unseen how does it affect us as humans?
This soil ecosystem is actually vital to our survival as humans because it is these organisms and their daily interactions and symbiotic relationships, with each other and plants, which create the perfect balance of conditions in the soil necessary to grow thriving food crops and other plants.
Plants need a balance of proper soil structure, water, nutrient availability, nutrient cycling and natural defense systems to really thrive. Plants use energy from photosynthesis to secrete exudates (Chemicals which are similar to pheromones in humans.
These exudates are made up of carbohydrates and proteins) through their roots. These exudates attract soil microorganisms such as bacteria, fungi, nematodes and protozoa to the plant’s roots. Microorganisms feed off of these carbohydrates and proteins (exudates) and exchange nutrients in the plant’s root zone in return. In fact, a plant secretes certain exudates to attract a certain amount and certain kinds of soil organisms based on the nutrients it requires. It is through these natural relationships (formed over millions of years) that plants and soil organisms create optimal conditions for their survival such as:
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Optimal soil water retention and drainage so plant roots and organisms can get enough water without being suffocated or rotting from too much water
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Optimal soil aeration so plant roots and living organisms can get enough oxygen
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Soil strength: the pathways and binding functions provided by soil organisms through their movement in the soil specifically strengthen top layers of soil, increasing resilience against compaction from heavy rain or human activity atop.
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Plant available nutrients and nutrient cycling. Any soil has all the nutrients (potassium, nitrogen and phosphorous) and micronutrients
(calcium, boron, iron, zinc) needed to sustain plant life; however, these nutrients are not in forms that plants can use right away. Microorganism activity converts the above nutrients into forms the plants can use and in the proper rates and amounts the plants need.
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Nutrient Retention: certain soil organisms immobilize (retain nutrients in their bodies) nutrients. The only time these nutrients are released is when the above organisms die or are eaten, and in the decay or digestion process nutrients are released from their bodies in plant available form.
This immobilization process prevents nutrients from leaching out of the soil.
A brief note on negative effects caused by chemical fertilizers
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Chemical fertilizers are able to put nitrogen, phosphorous and potassium into the soil in plant available form, but these fertilizers cannot be inputted in portion sizes and rates that plants require, so the fertilizer is inputted all at once and often leaches out of the soil before properly helping the plant while also poisoning ground water. In fact, chemical applications of phosphorous become unavailable to plants in seconds.
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Important relationships between plant roots and microorganisms will not form if plants become reliant on chemical fertilizers because plants can get “free” and “easy” nutrients from fertilizers and will therefore, bypass the process of obtaining nutrients from soil organisms.