The Value of Soil
Soil is an ecosystem that provides nutrients for plants, absorbs and stores water, filters pollutants, and provides many other foundational benefits to farms, forests, and human beings. Soil provides the habitat necessary for life-supporting soil microbes to thrive and diversify so that the local ecosystem and broader landscape communities can flourish and function effectively.
The soil food web describes an underground living community of organisms and microorganisms and how their interact with plants and animals. Where a food chain is linear, a soil food web is distinct as a cyclical series of symbiotic relationships. The web is made up of participants transferring energy and converting it to different forms for immediate use as food or to be stored in chemical form. A functioning and thriving soil food web is crucial to soil health.
Soil health, or soil quality, is the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans. This means it is critically important to manage our soils so they support people today and sustain future generations.
Soil degradation is the long term decline in soil’s productivity and its environment moderating capacity. It is also the inhibition of soil resilience, which is its ability to restore itself.
Soil erosion is the displacement of soil from where it form, by agents like wind and water, and its deposit at a lower site. Even though soil erosion occurs naturally, that is a slow and constructive process. Anthropogenic accelerated soil erosion, however, destroys soil structure, root depth, soil fertility and surrounding ecosystems.
Soil structure is the size, shape and arrangement of solids and voids, continuity of pores and voids, their capacity to retain and transmit fluids and organic and inorganic substances, and ability to support vigorous root growth and development. Soil structure is crucial for soil fertility, productivity, and decreased erosion.
Desertification is the unnatural degradation of land in arid, semi-arid, and dry dub-humid areas caused by human activities and climate events like prolonged droughts and floods. Desertification is experienced on 33% of the global land surface and affects over one billion people.
Annually, there is a global loss of 75 billion tons of soil / year. This costs roughly $400 billion/year. Soil erosion from agriculture in the United States costs roughly $44 billion/year. More than 70% of soil in North America has already been degraded.
Fostering Soil Health
Minimal soil disturbance
Soil disturbance can damage soil structure and soil function. This can happen through physical means such as tillage and compaction, or chemical means through fertilizers and other inputs. Disturbance diminishes the health of the soil by killing critical soil microbes, breaking apart aggregates, and disrupting supportive relationships between plant roots and soil microorganisms.
Diversity in soil and plant life
The key to improving soil health is ensuring that food and energy chains and webs consist of many different types of plants or animals. Biodiversity is critical to a successful agricultural system. A diverse and fully functioning soil food web provides for nutrient, energy, and water cycling that allows a soil to express its full potential.
Living roots in soil
Healthy soil is dependent upon how well the soil food web is fed. Living roots provide easily accessible food for soil microbes, and so should be maintained year-round. This helps them cycle nutrients that plants need to grow. Sugars from living plant roots, recently dead plant roots, crop residues, and soil organic matter all feed the critical soil food web.
Keep soil covered
Soil cover conserves moisture, reduces temperature, intercepts raindrops (to reduce their destructive impact), suppresses weed growth, and provides habitat for members of the soil food web that spend at least some of their time above ground.
Soil health benefits include…
- Increased agricultural yields
- Reduced inputs
- Reduced costs of chemical inputs
- Lower fuel and equipment costs
- Improved crop health and quality
- Increased resilience to disease and pests
- Improved water retention
- Resilience to extreme weather like droughts, flooding, and heat
- Increased and quicker processing of waste
- Soil carbon sequestration
- Reduced greenhouse gas emissions
- Improved public health with reduced pollution and increased nutrition
- Enhanced food security
- Restoration of desertified land and depleted soils
- Increased carrying capacity of productive land over time
- Improved soil resilience, the ability for the soil to regenerate itself, restoring critically lost topsoil
- Lal, R. (2007). Soils and sustainable agriculture. A review. Agronomy Sustainable Development,28, 57-64. doi:10.1015/agro.2007025
- Lal,R. ( 2003). Soil erosion and the global carbon budget. Environment International, 294, 437-50. doi:10.1016/S0160-4120(02)00192-7
- Bronick & Lal, 2004, Soil structure and management: a review. Geoderma, 124, 3-22. doi:10.1016/j.geoderma.2004.03.005