As we learned in Microbial Growers, the soil we use as a growing medium is full of beneficial microorganisms that are essential to plant health. In this post, we’ll dig deeper into the soil microbial community, learning about the products these microbes produce. We’ll explore how microbes can affect soil longevity, and discover the best practices for preserving and supporting these essential microorganisms.
The Life in Your Soil
Your soil is home to billions of microbes, organisms so small you can only see them with the help of a microscope. These microbes include bacteria, fungi, algae, actinomycetes, protozoa, and even minuscule worms called nematodes. The composition of soil can differ from place to place, but all healthy soil contains the essential microbes needed to sustain plant life.
Soil microbes are constantly at work. If you’re looking for the biggest workhorses, look to bacteria, the most abundant of all microbes. One teaspoon of soil typically has anywhere from 100 million to 1 billion beneficial bacteria. These microbes help with water dynamics, nutrient cycling, and disease suppression in plants.
Bacteria also work closely with fungi, a partnership that’s likely older than land plants themselves. Most scientists believe that the colonization of Earth by plants was due in part by this symbiotic relationship. Bacteria help in the decomposition of organic matter, turning decaying material into nutrients that feed plant growth. Even when the microbes themselves die, they release beneficial nutrients that improve soil quality.
What Are Microbial Products?
Microbial products are exactly what they sound like, substances that microbes produce. Included in these products are metabolites, which are formed during metabolism. All soil microbes produce primary metabolites, but only certain types of microbes produce primary and secondary metabolites.
Primary metabolites are essential to the microbe itself, whereas secondary metabolites are chemical signals secreted as a means of communication. By producing secondary metabolites, microbes effectively communicate with and influence other microbes in their environment.
Microbial products created in the rhizosphere—the zone of influence around a plant’s roots—can facilitate important aspects of plant health and growth. Let’s take a look at a few important bacterial products.
Hormones are an important bacterial product that help regulate plant growth. These include phytohormones such as auxins, which are involved in root formation and shoot development. They help plants with everything from stem elongation to pore closure during drought.
Other hormones help with disease resistance, inhibiting parasite growth and fighting plant pathogens.
Bacteria help cycle important macronutrients, like nitrogen and phosphorus, by making them available for uptake. They do this by producing specialized proteins called extracellular enzymes. These enzymes help break down nutrient-rich molecules into bioavailable forms for plant uptake.
Another important plant nutrient is iron, which is made available by bacterial chelating compounds called siderophores. When plants have more iron, they better perform essential processes like photosynthesis and respiration. Ferric iron found in soil has very low solubility, which means it won’t easily dissolve for plant nutrient uptake. Siderophores are responsible for interacting with this iron and make it accessible to plants.
All of these microbial products are important for helping plants thrive. But these products also tell us a lot about how microbes are the drivers of natural, sustainable agriculture. By keeping the soil microbiome healthy, we can improve the hardiness, health, and yield of our plants in a way that supports the longevity of our soil.
Supporting The Soil Ecosystem
It’s no secret that modern farming is destroying soil across the globe. It’s estimated that over a third of the Earth’s topsoil will soon be gone because of it. However, all hope is not lost. Scientists believe that microbes can be used to reinstate the fertility of degraded soils. It will take time, but there’s a way back.
The biggest thing we can do to facilitate this repair is to grow organically. Organic growing reduces the negative environmental impact we have on the soil, avoiding harsh chemicals that damage microbial life. Instead of focusing solely on our plants, we can feed the entire system, fueling the microbes that promote a healthy growing environment.
In the end, when we protect the soil and its microbes, more than just our plants reap the benefits. When the microbial life in your soil works in harmony, the result is high quality, sustainable plant growth.
- Amara, Ummay, Khalid, Rabia and Haya, Rifat (2015). “Soil Bacteria and Phytohormones for Sustainable Crop Production.” Bacterial Metabolites in Sustainable Agroecosystem pp 87-103. Retrieved from https://link.springer.com/chapter/10.1007/978-3-319-24654-3_5
- Bell, Colin. “Using beneficial soil microbes to improve plant growth.” Mammoth Microbes.
Retrieved from https://mammothmicrobes.com/portfolio/using-beneficial-soil-microbes-to-improve-plant-growth/
Imtiaz Muhammad, Liyakat Imtiaz et. al (2016). “Bacteria and fungi can contribute to nutrients bioavailability and aggregate formation in degraded soils.” Microbial Research. Volume 183: 26-41. Retrieved from https://www.sciencedirect.com/science/article/pii/S0944501315300288
- Ingham, Elaine R. “Soil Bacteria.” USDA National Resources Conservation Service. Retrieved from https://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/soils/health/biology/?cid=nrcs142p2_053862
- Hoorman, James J and Islam, Rafiq. “Understanding Soil Microbes and Nutrient Cycling.” Retrieved from https://ohioline.osu.edu/factsheet/SAG-16
- Karlovsky, Petr (2008). “Secondary Metabolites in Soil Ecology,” p 1-3. Retrieved from http://content.schweitzer-online.de/static/catalog_manager/live/media_files/representation/zd_std_orig__zd_schw_orig/017/911/827/9783540745426_content_pdf_1.pdf
- “Microbial Growers: Feeding Your Soil.” BlueSky Organics. Retrieved from https://blueskyorganics.com/growing-science/microbial-growers/
- Quastel, J H (1865). “Soil Metabolism.” Annual Review of Plant Physiology. Vol 16:217-240. Retrieved from https://www.annualreviews.org/doi/abs/10.1146/annurev.pp.16.060165.001245?journalCode=arplant.1
- Royal Queen Seeds Contributors (2018). “Why soil microbes are vital within your cannabis garden.” Retrieved from https://www.royalqueenseeds.com/blog-why-soil-microbes-are-vital-within-your-cannabis-garden-n878