Fungi and moss on forest floor

Soil Management and Ecological Agriculture

Background on Healthy Soils and Farming

Topics

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

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

Resources

The Relationship Between Agriculture and Climate

How climate change impacts agriculture

The impacts of climate change on agriculture are many and varied, but perhaps the most important thing to understand is that climate change manifests in each locality differently. Some regions are projected to receive more rainfall, others less. Some regions are seeing minor and relatively gradual changes to historical seasons, others are experiencing abrupt collapse of annual weather patterns that agriculture depends on to function, such as monsoon seasons in the tropics.

A common thread and threat among all regions is unpredictability. While we are able to observe and project certain macro trends important to agriculture, such as increasing amounts of rainfall in a growing season or the total number of growing days in a year, weather patterns day to day are increasingly erratic. Take increased rainfall, in most regions experiencing this, the rain increasingly comes in large rain events creating unpredictable flood like conditions. In some regions, these rain events tend to occur at inopportune times for production, such as during spring planting when it is essential to get large machinery into fields. At this writing, we are observing this exact phenomenon across America.

Erratic increased rainfall is just one example of a specific threat created by climate change that today’s farmers face. Other threats include but are not limited to erratic frost and thaw dates, new and increased pest vectors, crop species migration, increased annual temperatures and extreme heat events, and increased disease exposure to agricultural workers.

This last point is important to note. Not only is farming becoming more difficult in the face of climate change, but in certain scenarios it is becoming more physically dangerous to those performing work in the field.

How agriculture impacts climate change

Agriculture impacts climate in a number of ways. Many aspects of modern agriculture produce greenhouse gasses. Use of fossil fuel burning machinery, large scale animal production, use of fossil fuel based inputs such as chemical fertilizers, and our food distribution system all add greenhouse gasses to the atmosphere.

Additionally, the way we manage land in any given production system can at minimum reduce the lands ability to sequester carbon and at worst add additional carbon to the atmosphere.

All of these sources of greenhouse gases help to make agriculture responsible for roughly 12% of humanity’s impact on global climate. (IPCC)

How farmers are adapting to climate change

It is important to recognize that there are two separate yet interrelated questions regarding agriculture’s response to climate change. One is how do farmers adapt to new climate conditions, or what do farm businesses need to continue operating season to season? The other is how can agriculture mitigate its contribution to climate change? For each question there are unique and independent answers as well as key strategies that address both concerns simultaneously.

When considering how farmers adapt, it is again crucial to keep in mind the complexity of both climate changes across the globe and agricultural production systems. Just as the impacts climate change has on agriculture are diverse and varied, farmers’ responses to climate change are equally diverse and regionally distinct. The term agriculture captures an amazing amount of food crops and production systems.

To truly understand what adaptations are necessary in any given region, it is important to check which crops are grown there, what kind of production systems are used to grow them, and what specific changes in climate are occurring. Regionally located industry groups, state departments of agriculture, local agriculture non-profits, agriculturally focused educational institutions, and state meteorologists are all great sources to consult when investigating this question.

How agriculture can help mitigate climate change (e.g. carbon drawdown)

When considering how agriculture can mitigate climate change, there are two broad strategies to be aware of. The first is clean energy production. Farms are large, undeveloped parcels of land and usually contain patches of ground that are not ideal for production and or large outbuildings essential to the farm’s operations. Both are ideal locations for solar arrays. Unproductive ground can also be used for wind energy production and other emerging energy technologies such as biodigesters. This energy can then be used on farm or sold back into the grid.

The second strategy is carbon sequestration in farmland. This is accomplished by changing management practices within an existing productions system. Typically, increasing the amount of perennial plant species in an operation, minimizing tilling, and keeping ground covered with living crops as much as possible increase carbon sequestration. These management practices are often the strategies that help farmers both mitigate and adapt to climate change. Commonly referred to as soil health building practices, they usually improve water infiltration and holding capacity of soil, mitigate temperature extremes, reduce erosion, and improve the nutrient balance within soils. All of these outcomes help support crop resilience in the face of erratic weather patterns created by climate change.

Soil Carbon Sequestration

  1. What is carbon sequestration?
  2. What is soil carbon sequestration?
  3. How do soils store carbon?
  4. Soil Organic Matter
  5. What are some benefits of soil carbon sequestration?
  6. Farming methods to sequester carbon in soil

Soil Carbon Sequestration

  1. What is carbon sequestration?

    Carbon dioxide is one of the most commonly produced greenhouse gases found in the atmosphere. Most atmospheric carbon comes from natural and human activities such as combustion of fossil fuels for energy use. Carbon sequestration is the process of capturing atmospheric carbon and storing it in the ocean, in soil, or in vegetation.

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  2. What is soil carbon sequestration?

    Soil carbon sequestration is the process of removing carbon dioxide from the atmosphere through plants which have the ability to take in carbon and store it. Soil plays a major role in maintaining a balanced carbon cycle in addition to the benefits it provides to agricultural production and ecosystem function.

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  3. How do soils store carbon?

    Plants receive and return carbon in their leaves through photosynthesis and respiration. Carbon that remains in a plant is then consumed by animals or directly added to soil through decomposition. The primary way that carbon is stored in soil is through soil organic matter.

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  4. Soil Organic Matter

    Soil organic matter is the organic component of soil and consists of three primary parts including fresh plant residue, decomposing organic matter, and stable organic matter (humus). Soil organic matter holds nutrients so they are available for crops and plant growth, retains moisture, increases water infiltration, and stores carbon. Carbon can remain stored in soils for many years or can quickly be released back into the atmosphere depending on climate, drainage, vegetation, and management.

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  5. What are some benefits of soil carbon sequestration?

    Soil carbon sequestration can be a tool to mitigate climate change by removing carbon that is constantly being released into the atmosphere, restoring balance to the global carbon cycle. Soil carbon is also  beneficial to farmers by improving soil fertility, reducing erosion, and increasing resilience during periods of droughts or floods. Because of its benefits, many farmers incorporate soil conservation into their farming methods in order to maintains healthy soils full of carbon.

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  6. Farming methods to sequester carbon in soil

    Rotational grazing

    Rotational grazing involves dividing pasture into different sections called paddocks. Cattle are left to graze on a paddock for a short period of time and then moved to a separate paddock. Allowing cattle to graze in a small area of time promotes uniform growth of plants. After the cattle are moved to a different paddock, plants are left undisturbed to regrow. As plants mature, they become less nutritious. Rotational grazing is beneficial because cattle spend shorter periods of time on plots of land, which allows more time for growth.

    Cover cropping

    Cover cropping is the practice of growing crops such as clover or small grains for ground protection and soil improvement between period of regular crop production. Land that contains high amounts of biodiversity absorb and sequester more C than land with less diversity because more organic material is added to the soil.

    Conservation tillage

    Unlike conventional tilling, conservation tilling resists soil disturbance and encourages land to lay fallow when land is not in production. Practices such as mulch tillage leave crop residue on the soil surface which improve soil structure. Conservation tillage reduces soil erosion, improve water quality, and increases carbon concentration in soil.

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References

Ecological Agriculture

Ecological agriculture captures the strengths of natural ecosystems to develop agricultural ecosystems that are productive and resilient. Natural ecosystems are characterized by efficient capture and use of energy and water, biological diversity above ground and in soil, self-sufficiency (only needing sunlight and water), self-regulation (diversity promotes strong defense mechanisms to disease and pests), and resiliency. Through habitat conservation management, ecological farming builds these strengths into managed agricultural ecosystems to optimize productivity. This means minimal disturbance, minimal use of fossil fuels and chemical inputs, and minimal waste. Ecological farming might include diversified production and methods like perennial cropping, crop rotation and rotational grazing, livestock integration, cover crops, and no-till or conservation tillage. However, the focus is on performance and not practices, which vary by farm and location. The ultimate goal is to facilitate conditions that enable beneficial organisms and healthy plants to thrive, while deterring pests. This might also be called resource-conserving agriculture, or agricultural sustainability, which emphasize food production that makes the best use of nature’s goods and services while not damaging them.

Criticisms: Impracticality, Expense, and Inefficiency

The greatest criticisms of ecological farming are that it reduces yields and profits, is more expensive, requires more land, is not scalable, and is inefficient.

It is true that financially and practically, ecological farming is a challenging approach to take because it does not receive the variety of federal supports that industrial agriculture does. These include subsidies paid for commodity crops, insurance, and market access. Industrial agriculture also is facilitated by the many loopholes in agricultural and environmental laws. On a level playing field, however, industrial farms would struggle to compete against the benefits offered by ecological ones, without disaster relief, crop insurance, and subsidies that provide relief that diversity and resiliency provide in less degraded landscapes. Ecological resiliency reduces risk and results in many avoided costs that also make industrial agriculture less affordable, as discussed above. Because it is resilient and reduces risk and harms from weather, disease and pests, and loss of natural resources, it is cheaper in the long-term, and with reorganized federal priorities, ecological farming would be the cheaper option today as well.

Contrary to criticism, research shows ecological systems actually often result in higher profits, nutritional quality, and comparable or greater yields per acre relative to industrial systems. Ecological farming has been shown to be more efficient, diverse, and resilient, than its mechanized counterparts.

Ecological Farming is Diverse, Efficient, and Resilient

By prioritizing soil health and biodiversity in soil and above ground, ecological management promotes energy efficiency, nutrient cycling, water infiltration and retention, and carbon cycling. Healthy soil is rich in organic content, which means it is energy-rich – and thus a valuable resource that provides nutrients and energy for productive and high-quality plant growth – reducing the need for energy and chemical inputs, and a host of other benefits like reduced erosion, watershed management, and climate regulation. Crops are grown that are best suited to the landscape and season, require less inputs, and deliver more nutrition, instead of management reflecting demands of agribusiness and commodity markets. Learning from the efficient energy and water conversion processes of natural ecosystems, ecological management uses practices that improve ecosystem function, such as cover cropping, crop rotations, covering the ground with plant residues, and no-till. Studies show energy consumption for conventional tillage is significantly higher than for no-till crop production. Reducing tillage also improves soil health and reduces soil erosion, which is detrimental to soil and farm productivity. Pasture based animal production is significantly less energy intensive than using feed for animal production, and it improves the health of the animals, the quality of the products, and health of the soil and landscape. For example, in a survey of US dairies, energy use varied from as low as 1670 MJ per year per animal for a pasture-based dairy to as high as 5893 MJ for a hybrid facility. Grass-based livestock also minimizes the energy intensity involved in feed production, processing, and transport.

Rather than compromising yield-size as critics claim, ecological farming not only can increase yields, but also profits and nutrition. Preserving natural resources like soil and water contributes to the long-term sustainability and productivity of agricultural ecosystems. Crops and perimeter plants around crops are grown to provide protection from pests, which also enhances soil health. Leguminous crops are introduced to biologically fix nitrogen, reducing reliance on chemical inputs and increasing soil organic matter, which improves nutrient retention and water infiltration and reduces erosion. Nitrogen cycling is also improved with manure and residues, which in turn reduce losses and costs of inputs and remediation. Perennial cropping systems also reduce chemical use and can result in as much as 35 times more nitrogen efficiency than annual monoculture cropping.

Research shows that ecological management can produce equal, and in many cases higher, yields than systems with intensive chemical and fossil fuel use. One study showed that measures to improve environmental performance in crop production systems have been shown to increase yields by 79-200%. Data shows that ecological farms increase productivity by more efficient use of the biotic energy embedded in biomass and less energy inputs. Another study demonstrated how over the course of a decade, farmers in 286 projects in 57 countries improved crop productivity, reduced pesticide use, and increased water use efficiency and carbon sequestration.

Ecological farming enhances plant growth by promoting microbial diversity in the soil. In addition to considering productivity and taste, crops are selected that are resistant to local pests, contributing to the resiliency of the farm. Improving soil health reduces erosion, nutrient runoff, and improves watershed function and system resiliency, reducing risk and damage. Biodiversity provides defense mechanisms against pests and disease outbreaks. Fungal-based soil food webs are common in ecological systems and are more adapted to drought than the bacteria-based food webs common in industrial systems. By enhancing soil health and biodiversity, ecological farms also reduce air pollution, soil and water contamination, and preserve carbon sinks, helping to mitigate climate change and providing other immense benefits to public health and the long-term sustainability of our food system.

References

Fred Magdoff, Ecological Agriculture: Principles, Practices, and Constraints, 22 Ren. Agric. & Food Sys. 109 (2007).

J.N. Pretty, et al., Resource-Conserving Agriculture Increases Yields in Developing Countries, 40 Envt’l Science & Tech. 1114 (2006).

Nathan Pelletier, Energy Intensity of Agriculture and Food Systems, 36 Annual Rev. of Env’t & Resources 223 (2011).

Ricardo Cavicchioli et al., Scientists’ Warning to Humanity: Microorganisms and Climate Change, 17 nature reviews | microbiology 569 (2019).

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