Cover Image Source: Babur & Dindaroglu, 2020

By Lu Yu

When you look at the soil as a living entity, because soil is a very large reservoir of biota, microorganism, macro-organism,  earthworms, termites, and of course the microbiota, then soil behaves like a living entity. In other words, soil is a living biomass. Soil supports life, and life is supported by soil.

— Dr. Rattan Lal, Renowned Soil Scientist, WSU Interview

Soil does not occupy much pore space in popular imagination. When soil surfaces, it’s often taken for granted as a mere substance that delivers food and plants, something that makes up the ground walked upon, simply dirt that children should not touch, or the particles we breathe during strong winds. These limited understandings have disconnected us from the soil and the larger ecosystem we inhabit, which has driven haphazard chemical use that degrade ever-shrinking fertile farmlands, steep decline in the nutrient density of the foods we feed our children, rising volumes of agrochemicals in waterbodies, resulting loss of habitat and biodiversity, and a looming human health crisis from these factors combined. As ecosystem disruption and climate change worsen, if there was one thing on which we can concentrate our efforts, money, and time to address these issues all at once, what would it be? 

The answer is Life in soil. 

Soil is an ecosystem, comprising minerals (in the form of sand, silt and clay), organisms both micro and macro, and organic matter, which is the wastes and residues from plant and animal sources at various levels of decomposition. These three elements interact with each other intimately in the Soil Food Web. 

Image source: USDA, Natural Resources Conservation Service

Living Roots & Microbes

Microorganisms and their symbiotic relationship with living plant roots form the foundation of the soil ecosystem. Plants harvest only sunlight and carbon from aboveground and rely on soil for all other nutrients. When a plant requires a certain amount of a nutrient, it produces sugars and sends them down through the roots as exudates, which bacteria and fungi feed on in exchange for the exact amount of the exact nutrient the plant requires. According to Dr. Elaine Ingham, all the nutrients that plants will ever need for hundreds of years or more are already present in sand, silt, and clay particles, but not accessible to plants. Here, microorganisms play the crucial role of converting these nutrients into plant-available form so plants can readily absorb them. Through the process of microorganisms feeding on each other and being consumed by larger macroorganisms, excess nutrients are also released. Plant-available nutrients in the soil are constantly replenished by soil microbiology, who are nature’s workers laboring around the clock to sustain life aboveground.

Both living roots and microorganisms need to be present for a healthy soil. 

In one gram of soil, there are approximately 10 billion microorganisms and thousands of different microbial species. Different microbes thrive in different conditions - humidity, temperature, oxygen, light, altitude - and it’s this very diversity that lends resilience to soil, land, and the agricultural and food systems we rely on today in the face of climate change effects.

Soil Structure: A House that Microbes Built (for Air, Water, and More Microbes)

A closeup of soil aggregation. Image Source: Soil Dynamics

Bare roots in chemically treated soil, without the protection of soil structure. Image Source: Green Cover.

Soil under diverse green cover with no use of fertilizers shows well-developed soil structure bound together by biological slime, promoting healthy root growth. Image Source: Green Cover

“We can improve nearly everything in life by paying attention to the structural integrity and functional capacity of the soil under our feet. The Soil Sponge is the basic infrastructure that makes life on land possible. ”

— Didi Pershouse, Author & Educator, Land and Leadership Initiative

“Soil Sponge” is healthy soil that is a living system that absorbs, filters, and stores water, air and carbon, holds landscapes together, and provides nutrients to the entire food chain in this ecosystem. A healthy soil sponge begets better air quality, cleaner water supplies, cooler temperatures in the face of global warming, more biodiversity, less erosion, less money spent on infrastructure damaged by erosion, less money spent on public health and disaster recovery. The water cycle, carbon cycle, and nutrient cycle on this planet all depend on a healthy soil sponge, which is created and maintained by various other species. 

Thanks to the work of plants, fungi, bacteria, worms, insects and other species inside the soil, what would otherwise be just sand, silt, and clay is now bound together by carbon-based biological glue, slime, and threads into a structure with pores and passageways that house air, water, nutrients, roots, and allows more beneficial soil biology to proliferate. The Soil Sponge’s ability to maintain stores of water and nutrients means more plant roots can be nourished for longer, plants can photosynthesize longer and capture more carbon from the atmosphere, excess rainwater can be absorbed preventing floods and droughts, a restored hydrological cycle that controls the earth’s heat dynamics and significantly cools the planet, and overall improved resilience realized for land and life on land during natural disasters.

To build back the Soil Sponge, regenerative soil management is key. These methods not only produce stronger, more nutritious crops, but also create optimal living conditions for the various species of soil organisms to carry out their essential functions to bring back and maintain the soil sponge, sustaining life and its processes on this planet.

Practices for Soil Health

Image Source: USDA Northwest Climate Hubs

Soil health principles follow Nature’s way of land maintenance and collaborates with other species to maintain a healthy soil sponge. 

Minimal or zero disturbance of the soil allows all the members of the soil food web to carry on its function uninterrupted. Conventional agriculture involves ploughing lands for seeding and harvesting, which breaks the soil structure and the soil food web, disrupting the underground ecosystem and exposing life within to harsh elements above ground. This reduces the population of active soil microbes who are very sensitive to changes in their environment, more than plants and animals are. No-tillage (for example, direct seeding without heavy machinery) or minimal tillage (tilling only when needed) are two ways to minimize this disturbance.  

To encourage a diverse, well-fed soil microbial community, soil needs to be covered all seasons of the year by a variety of green cover, providing living roots, organic matter, and protection from the elements (erosion from sun, water, wind or natural disasters like floods or drought). Integrating animals into cropland consistent with the needs and carrying capacity of the land allows for nutrient cycling through the spread of animal manure, and resilience of the soil food web and the aboveground ecosystem.

Sustainable Soil Management Catalogs for 192 Countries

Save Soil has compiled more than 700 unique sustainable soil management practices across the world. SSMs are cataloged for each agro-ecological zone in each country, comprising region-specific conditions and soil types. Visit here for more details.