By Dr. Daniela Vergara
Soil is more than a surface for growing plants. It is a living, dynamic ecosystem that supports life across the planet. In one handful of soil, there are billions of bacteria, fungi, and other microorganisms that drive the biological interactions essential for ecosystems, agriculture, and climate stability.
What Is Soil?
Soil is a combination of mineral particles, pore spaces filled with water and air, organic materials (both living and dead), and dissolved nutrients. These components bind together to form stable structures called aggregates.
Soil Texture
Soil texture refers to the mix of three types of mineral particles [1]:
- Sand: 0.0021 to 0.078 inches
- Silt: 0.000079 to 0.0021 inches
- Clay: less than 0.000079 inches
Texture is determined by the geology of the location and cannot be changed through management. The ideal soil is often described as [1, 2]:
- 45 percent mineral particles
- 5 percent organic matter
- 50 percent pore space for air and water
This mix supports good water infiltration, drainage, and root development.
Organic Matter and Carbon
Organic matter can be influenced by factors including decomposed plant materials, living and dead soil organisms, and substances like sugars, fats, lignin, and cellulose. Some components, like humic and fulvic acids, bind with clay particles and persist longer in the soil. Others break down quickly and respond to management practices [1].
Returning crop residues to the soil helps increase organic carbon, building a more resilient and balanced system. Reactive forms of soil carbon include actively decomposing materials and living microbial biomass. These can be measured using tools like permanganate oxidizable carbon or particulate organic matter [1].
Management influences this pool of carbon. For example, growing crops with low residue or removing plant material can reduce active carbon. A balanced rotation of crops with varying carbon-to-nitrogen ratios helps microbes process inputs effectively and stabilize carbon in the soil [1].
Soil Organisms
Healthy soil is full of life. In just one gram of surface soil, you might find [1]:
- 100 million bacteria
- 10 million actinomycetes (fungi)
- 10,000 protozoa
- 10 to 100 nematodes
A single cubic yard of soil can contain up to 1,000 earthworms, along with insects, amphibians, reptiles, and small mammals [1]. These organisms decompose organic material, cycle nutrients, form pore channels, and contribute to soil structure. Fungi also form partnerships with plant roots that help with water and nutrient uptake.
What Is Soil Health?
Soil health is the ability of soil to function as a living, dynamic system that sustains plants, animals, and people. Healthy soil provides [1-3]:
- Clean air and water
- Abundant crops and forests
- Resilient grazing lands
- Habitat for pollinators and wildlife
- Stable infrastructure and landscapes
These outcomes are made possible through five key soil functions [4]:
- Water Regulation: Directs rain, snowmelt, and irrigation water, helping prevent runoff and erosion
- Support for Life: Sustains diverse plant and animal life
- Pollution Buffering: Filters and neutralizes pollutants through minerals and microbial activity
- Nutrient Cycling: Stores, transforms, and moves carbon, nitrogen, phosphorus, and other nutrients
- Physical Support: Anchors plant roots and supports structures and artifacts
Healthy soil has stable structure, stores water in small pores, hosts a diverse array of life, is protected by living or dead plant cover, and cycles nutrients efficiently. It responds to what is planted and how it is managed.
Principles for Managing Soil Health
There are four core practices that improve and maintain soil health [4]:
1. Maximize Living Roots
Roots feed soil organisms and maintain a biologically active zone called the rhizosphere. Plants release compounds into this zone that stimulate microbial activity. Keeping living roots in the soil for as much of the year as possible supports a healthy food web.
Effective practices include:
- Planting long-season crops
- Using cover crops after harvest
- Minimizing bare or fallow periods
2. Minimize Soil Disturbance
Tillage and excessive chemical use damage soil structure and disrupt microbial communities. This leads to more erosion, lower water retention, and reduced nutrient cycling.
Reducing disturbance results in:
- Better soil structure
- Increased microbial activity
- Improved water storage
- Reduced costs for fuel, labor, and inputs
In grazing systems, rotating livestock and allowing rest periods also reduces disturbance.
3. Maximize Soil Cover
Soil should remain covered throughout the year using crop residues, cover crops, or living mulches. Cover protects against erosion, stabilizes temperature, and supports biological activity.
Cover crops such as rye, radish, clover, oats, and legumes help:
- Increase organic matter
- Improve infiltration and reduce runoff
- Retain nutrients
- Provide forage for livestock
- Support pollinators and beneficial insects
Programs like EQIP and CSP can support these practices.
4. Maximize Biodiversity
Biological diversity enhances pest resistance, nutrient cycling, and productivity. Above-ground plant diversity supports below-ground microbial diversity.
Diverse systems:
- Are more resilient
- Require fewer chemical inputs
- Support beneficial insects and wildlife
- Reduce disease and pest problems
- Improve overall profitability
Low-diversity systems are more vulnerable and costly to manage.
Why Soil Health Matters
Soil health is essential for addressing global challenges. As demand for food rises, productive and resilient soils become more important. Farmers using soil health management systems see:
- Increased soil organic matter
- Higher microbial activity
- Better crop yields
- Greater carbon storage
- More water infiltration and retention
- Improved habitats for wildlife and pollinators
- Resilience against drought and extreme weather
Improving soil health is a path to sustainable agriculture and climate resilience.
Defining Soil Health
Soil health may be defined as “the continued capacity of soil to function as a vital living system, within ecosystem and land-use boundaries, to sustain biological productivity, promote the quality of air and water environments, and maintain plant, animal, and human health.” [3]
This definition emphasizes two key ideas: that soil health changes over time, and that living organisms are central to maintaining soil function.
A later definition describes healthy soil as a system that sustains productivity, supports biodiversity, filters pollutants, and retains water and nutrients [3].
A healthy soil should also avoid polluting the environment and help mitigate climate change by storing carbon [3].
A Healthy Soil
Soil is not the same as dirt. Dirt is inert, lacking life. Soil contains a rich mixture of minerals, organic matter, water, air, and a vast community of organisms [2].
Earthworms are a strong indicator of healthy soil. They help with aeration, decomposition, and nutrient cycling.
Several factors contribute to healthy soil:
- Physical structure and texture
- Chemical properties including pH and nutrient levels
- Organic matter content
- Biological diversity
- Water infiltration and retention
An imbalance in any of these can reduce soil health.
Additionally, a healthy soil:
- Cycles nutrients efficiently
- Supports strong plant growth
- Provides habitat for a wide range of organisms
- Filters pollutants and protects water quality
- Reduces erosion and surface runoff
- Stores water for plant use
- Supports buildings and infrastructure
And to know if you have a healthy soil you should look for:
- Healthy, vigorous plants
- Plenty of earthworms
- Good water infiltration
- Easy digging and cultivation
Maintaining soil health is essential for sustainable food systems and ecological integrity.
Soil Health versus Soil Quality
Soil quality often refers to how well soil supports a specific crop or short-term goal. Soil health considers broader ecological functions, such as [3]:
- Biodiversity
- Microbial activity
- Long-term nutrient cycling
- Resilience to disturbance
While short-term productivity can happen in poor-quality soils with high inputs, truly healthy soil supports long-term sustainability.
First, thanks for allowing me to learn more about topics that are outside of my area of expertise. Second, whenever you are cultivating your Cannabis sativa plants remember that soil is not just a growing medium. It is a complex, life-supporting system that we can manage for long-term productivity and resilience of our plants. By understanding and supporting soil health, we strengthen our farms, grow good crops, we have cleaner water, more stable ecosystems, a better future, and good weed!
References
1. Klopp, H., A. Bly, and D. Karki, What Makes Up a Healthy Soil?
(https://extension.sdstate.edu/what-makes-healthy-soil). 2025.
2. Gardeners, U.M.M., What Is Healthy Soil
(https://ucanr.edu/site/uc-marin-master-gardeners/what-healthy-soil). 2025.
3. (https://www.fao.org/agriculture/crops/thematic-sitemap/theme/spi/soil-biodiversity/the-nature-of-soil/what-is-a-healthy-soil/en/), F.a.A.O.o.t.U.N., NSP – What is a healthy soil? 2025.
4. Natural Resources Conservation Service, U.S.D.o.A.h.w.n.u.g.c.-b.n.-r.-c.s.s.-h., Soil Health. 2025.
