Last week we looked at how the soil can help us prevent floods and ensure water is available to plants in times of need. But, looking closer, we will learn that the role that soil plays in our ecosystems extends far beyond this. Soil is the basis for life. It provides us with most of our food, but it is much more than just a growing medium. To quote the late Paul Harvey, "Despite all of our accomplishments, we owe our existence to a six-inch layer of topsoil and the fact that it rains."

What is Healthy Soil?

Soil is a living, breathing thing that requires nurturing in order to survive. Healthy soil is home to an array of aerobic (oxygen requiring) microorganisms. These microorganisms, such as bacteria and fungi on the smallest scale, are the foundation of the soil food web. The soil food web plays an important role in carbon sequestration, which in turn increases the soil's ability to hold moisture, resist erosion and support biodiversity. When bacteria and fungi are present, larger microorganisms like protozoa, nematodes and the non-microscopic earthworms, beetles and other insects are also present to feed on them. All of these organisms work their way through the soil, consuming smaller species, breaking down soil particles, creating pathways for air and water to infiltrate while at the same time producing and distributing organic matter. An increase in the biodiversity of both macro and micro-organisms present in the soil is directly related to increased soil health. When you see a worm, working its way through the soil, it is there because there is food available for it. When birds or insects are poking around, they are enjoying a snack as well. 

Impact of microorganisms on soil health

There are three major roles that microorganisms play in the soil. First, as previously mentioned, they participate in creating the air and water pathways that are essential  for plant and microbial life. Secondly, they are responsible for releasing soil nutrients by breaking down both compost and soil particles making them available in a plant-ready form. Third, they communicate with plants to determine what nutrient the plant needs and exactly when it needs it. Plants send out signals through their root zones when a specific nutrient, such as phosphorous, is required; microorganisms source this nutrient and make it available to the plant in exchange for sugar. We don’t see much of the work that they do, but these microbial species are incredibly important to our soil, our plants and our ecosystems. 

Impact of chemical pesticides and fertilizers on soil health

Chemical pesticides and fertilizers are highly detrimental to healthy soil. They disrupt the delicate  soil food web and, as such, have negative, long term consequences. Many of these products contain high concentrations of salts. Microorganisms can not survive in high salt conditions and die as a result. As the smaller species die off, the larger ones cannot survive without  them for food. The more chemicals added to the soil, the more damage that is done, to a point where there aren’t any microorganisms left. Once the organisms  are gone, all the air and waterways they built will disappear leaving the soil without the capacity to hold water or support life. This type of poor land care practice can lead to degradation of formerly fertile soil. Carbon emissions generated during the application of synthetic fertilizers have resulted in one of the fastest growing emission sources in agriculture, contributing further to climate change. 

What does healthy soil do?

Now that we’ve established what healthy soil is, let's look at some of the things it does and how it impacts our ecosystems. 

Healthy soil

• Supports plants of all types, including but not limited to

• • Trees that absorb carbon dioxide from the atmosphere

  • Food gardens that provide nourishing, local food

  • Native plants that support native pollinators

• Is the foundation for ecosystem biodiversity

• Can sequester carbon and store it within fungi 

• Can absorb water during heavy rains and make it available to plants as needed

• Regulates ground temperatures

Healthy soil has a role to play in both climate change resilience and mitigation. Healthy soil sequesters more carbon, supports locally grown food to reduce our carbon footprint and is the foundation of ecosystem biodiversity, supporting both nutrient cycling and soil productivity. If we take care of the soil, it will take care of us. 

Building Healthy Soil

Building healthy soil isn’t difficult. It’s more a matter of giving back. What comes from the soil should go back to the soil. Food waste, especially fruit and vegetable waste can be composted. As can garden waste, leaves, tree branches (when mulched), and more. Leaving the leaves, grass cuttings, and ground litter to compost in place can allow for the natural covering of an area. If your neighbour likes to rake their lawn, use those for your own garden or compost pile. The more diverse the inputs to the soil, the more diverse the microbial species that will be present, increasing your garden’s resilience to climate change impacts.

References
de Goede, S. P. C., Hannula, S. E., Jansen, B. Morriën, E. (18 Apr 25). Fungal-mediated soil aggregation as a mechanism for carbon stabilization. The ISME Journal. https://pmc.ncbi.nlm.nih.gov/articles/PMC12106282/#:~:text=Recent%20studies%20found%20that%20fungi%20are%20responsible%20for%20sequestration%20and%20stabilization%20of%20up%20to%2075%25%20of%20plant%2Dderived%20carbon%20in%20natural%20grasslands

Cho, R. (18 Feb 2018). Can Soil Help Combat Climate Change? State of the Planet. https://news.climate.columbia.edu/2018/02/21/can-soil-help-combat-climate-change/#:~:text=Because%20microbial%20decomposition%20releases%20carbon,that%20protect%20carbon%20from%20microbes

Written by Julia Dupuis