Soil is often underestimated. To the casual eye it is simply the ground beneath our feet, but in reality, soil is one of the most complex ecosystems on Earth. A handful of fertile soil contains billions of microorganisms, more species than exist above ground, and an intricate web of physical, chemical, and biological interactions. It supports food production, regulates water and climate, cycles nutrients, and stores carbon. Without healthy soils, terrestrial ecosystems collapse.
Understanding soil functions is essential as every crop, every grazing system, and every tree depends on the invisible processes taking place in soil. By seeing soil not just as a substrate but as a living system with multiple roles, we can design farming systems that regenerate rather than degrade this precious resource.
This module explores the core ecosystem functions of soil: its role in the water cycle, carbon cycle, and nutrient cycling, its function as a habitat, and the interplay of physical, chemical, and biological properties. In this first section you will get a overview and refresh some backround information of the essential ecosystem cycles. These functions together define why soil is the cornerstone of regenerative agriculture and global ecological stability.
https://www.youtube.com/watch?v=OiLITHMVcRw
Soil is the interface between atmosphere, plants, and groundwater. It regulates how rainfall is absorbed, stored, and released, determining whether landscapes flood or thrive. When rain falls, healthy soil acts like a sponge, absorbing water into its pores, holding it for plant roots, and slowly releasing it to groundwater and streams. Soils with good structure, rich in organic matter, with stable aggregates and pore spaces can absorb several times more water than degraded soils. By contrast, compacted or bare soils repel water, causing runoff, erosion, and flash flooding.
The infiltration rate determines how quickly water can enter the soil. Aggregated, well-structured soils with root channels and earthworm burrows have higher infiltration. Once inside, water is held in micropores, available to plants. Organic matter is especially important: every 1% increase in soil organic carbon can increase water-holding capacity by 20,000–25,000 liters per hectare.
Here is a quick water holding capacity example
By holding water longer, soils buffer plants against dry spells. Regenerative practices that build soil organic matter and porosity such as cover cropping, reduced tillage, and diverse rotations also enhance drought resilience. Conversely, soils degraded by intensive tillage or loss of organic matter lose this buffer and suffer from crop failures under stress.
At the planetary scale, soils regulate evapotranspiration which is the combined process of evaporation from soil and transpiration from plants. This process drives local rainfall patterns and even influences continental climate systems. Degraded soils reduce evapotranspiration, contributing to desertification and altered rainfall regimes. Thus, soil management has direct consequences for regional and global climate stability. Learn here more backround infromation around the water cycle:
https://www.youtube.com/watch?v=0WGiLaAAEoo
Carbon is stabilized in soil through microbial processing, chemical binding to minerals, and physical protection inside aggregates. Healthy soils with diverse microbial activity and good aggregation can store carbon for centuries. Disturbances such as tillage or overgrazing disrupt these mechanisms, leading to carbon release back into the atmosphere. You can find a more detailed explaination of the stabailization processes here:
Soils are both a source and sink of carbon. Intensive agriculture has released much of the soil carbon built up over millennia, contributing to greenhouse gas emissions. Yet regenerative practices can reverse this, re-building soil organic carbon. We must therefore see soil not just as a fertility medium but as a lever for climate resilience.
Soils store more carbon than the atmosphere and all vegetation combined. This makes them a critical component of the carbon cycle and a central player in climate regulation. Carbon enters soils primarily through photosynthesis: plants capture atmospheric CO₂, convert it into sugars, and transport a portion into roots and exudates. These compounds feed soil microbes, which in turn stabilize carbon in organic matter. Dive deeper into the backround of the carbon cycle:
https://www.youtube.com/watch?v=xXo-9x1bSDU
Soil acts as both a reservoir and transformation hub for nutrients. Macronutrients such as nitrogen, phosphorus, and potassium, and micronutrients like zinc and boron, are stored in soil minerals and organic matter. Through biological and chemical processes, these nutrients are transformed into plant-available forms.
Management determines whether nitrogen cycles efficiently within the soil-plant system or is lost as pollution. To fully understand the nitrogen cycle please dive deeper into into it and refresh your knowledge:
Phosphorus is often bound in mineral complexes, requiring microbial or root exudates (organic acids) to release it. Potassium cycles more readily but can be depleted without replenishment. Both cycles illustrate the importance of soil biology in making nutrients accessible.
Manure, compost, and residues recycle nutrients back into soil. Soil organisms decompose this material, releasing nutrients gradually, reducing losses, and supporting long-term fertility. By cycling nutrients efficiently, soils reduce the need for external fertilizers, lower water pollution risks, and support balanced plant nutrition. Healthy nutrient cycles are a hallmark of regenerative systems.
https://www.youtube.com/watch?v=7Tidt0rpNvM
Soils host immense biodiversity: bacteria, fungi, protozoa, nematodes, earthworms, arthropods, and more. This community often referred to as the **soil food web,** regulates decomposition, nutrient release, disease suppression, and soil structure formation.