Soil-profile art is not akin to classic paintings with themes; rather, it resembles abstract art: and if you are used to thinking of soil as dirt, which is customary in our society, you are not keyed to find beauty in it.”  Hans Jenny, 1984

 

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Why soils?

2015 has been designated the International Year of Soils by the United Nations.  This designation has been embraced in the United States by the Department of Agriculture, the Soil Science Society of America and others. Many readers may be asking, “why?” This article will serve as an introduction to the topic and CIRS will post monthly submissions by experts on the particular value of soils. Our approach will focus on the rural but we will not limit our discussion to rural regions. There are many rich and productive soils being used in urban areas to sustain communities by providing space to grow food. And food production is our concern. Soil is the foundation of civilization and has been the key to human development over the past 13,000 years.

 

In this series of posts we will discuss soil formation, ecosystem functions of soil, soil loss, the economic value of soil, soils on pasture land, soils in crop production, soil and water, the politics of soil, soil and food security and carbon sequestration in soils. Expect a diverse and well regarded group of writers and look for them here the last Monday of every month.

 

What is soil?

Soil is the ecosystem beneath our feet.  It is composed of both organic and inorganic matter and is home to billions of living things. It is the basis for life on Earth providing nutrients to plants that are then consumed by animals (including humans). It is also important for water storage and purification. Soils, being very diverse, contribute to biodiversity, are the source of antibiotics, help us manage our waste products and provide us with food and fiber. Soil is not only a source for gases like oxygen and carbon dioxide in the atmosphere but also can serve as storage for them.

 

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Understanding the importance of soil is understanding the development, and in some cases downfall, of civilizations. Soil is the basis for agriculture which led to the settling of humanity and the creation of cities. Lack of soil stewardship in many cases led to the unsettling of communities.

 

“The soil is the great connector of lives, the source and destination of all. It is the healer and restorer and resurrector, by which disease passes into health, age into youth, death into life. Without proper care for it we can have no community, because without proper care for it we can have no life.”


Wendell BerryThe Unsettling of America: Culture and Agriculture

 

Soil and Civilization

The initial cultivation of soil started in about 11,000 BC in the Middle East. A change from a nomadic lifestyle to a settled one resulted. Building on that change in human ecology, innovations abounded: irrigation, aqueducts, plows and more plows, fertilizers, tractors, hybridization, preservation, refrigeration, genetic modification and more. All of these innovations either affected the use of soils or were reliant upon soils and their products.

 

At the end of the last ice age the Near East became wetter and warmer allowing for the rapid spread of grains humans relied upon for food.  This climate change resulted in a more stable food supply and eventually led to selection and cultivation of specific grains and plant traits. With a more stable food supply people became sedentary and villages grew. This in turn led to labor specialization and what we now know as civilization. 

 

People seemed to like this change and worked to improve systems for food production to make it both more efficient and reliable. As cultivation of the soil spread so did the impacts of that action. One theory states that irrigation, which allowed for higher crop productivity, may also have led to the demise of Mesopotamia through the accumulation of toxic salts in the soil. Soil erosion may have also contributed to the downfall of early civilizations and currently impacts residents worldwide.

 

Soil Loss

Living in California, we all know the impacts of the Dust Bowl on our state.  People moved here for opportunities that were gone from the southern plains as a result of mistreatment of the soil.

 

In the 19th and early 20th centuries a push was on to expand agriculture because of new machines and high prices for grain. Millions of acres of native grass were plowed up for wheat. By the time the drought hit in the mid-30s, soil covering about 150,000 square miles was basically bare. With decreased rainfall the light soil became victim to high winds and this valuable topsoil was picked up, forming dense clouds. Cattle were choked and pasture lands as well as crop lands were destroyed. As a result, 60 percent of the residents of the region migrated toward what they saw as opportunity.

 

The federal government’s response to this disaster was Public Law 74-46 passed in 1935.  This law recognized that "the wastage of soil and moisture resources on farm, grazing, and forest lands . . .  is a menace to the national welfare." As a result, the Soil Conservation Service (SCS) was established as an agency of the US Department of Agriculture. (Since 1994, the SCS has been known as the Natural Resources Conservation Service (NRCS) to better reflect the broadened scope of the agency's concerns.)

 

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“The Western States are nervous under the beginning change. Need is the stimulus to concept, concept to action. A half-million people moving over the country; a million more restive, ready to move; ten million more feeling the first nervousness.


And tractors turning the multiple furrows in the vacant land.”


John Steinbeck, The Grapes of Wrath

 

Valuing the Resource

There are many ways scientists and economists determine the value of soils.  Economists have assigned monetary values to soil loss, soil ecosystem functions, soil biodiversity and more.  Below is a table explaining some soil benefits to humans.

 

Soil Function

Benefit of Value to Humans

On-site

Off-site

Nutrient cycling

Delivery of nutrients to plants

Carbon storage improves a variety of soil functions

Enhances water and air quality

Storage of N and C can reduce greenhouse gas emissions

Maintaining biodiversity and habitat

Supports the growth of crops, rangeland plants, and trees

May increase resistance and resilience to stress

Reduces pesticide resistance

Helps maintain genetic diversity

Supports wild species and reduces extinction rates

Improves aesthetics of landscape

Water relations

Provides erosion control

Allows on-site water recharge of streams and ponds

Makes water available for plants and animals

Provides flood and sedimentation control

Groundwater recharge

Filtering and buffering

Can maintain salt, metal and micronutrient levels within range tolerable to plants and animals

Improves water and air quality

Physical stability and support

Acts as a medium for plant growth

Supports buildings and roads

Stores archeological items

Stores garbage

Multiple functions

Sustains productivity

Maintains or improves air and/or water quality

 

Economic valuation

The economic value of soil is determined by the benefits provided to society. To the economist, these benefits are reflected in people’s willingness to pay for them based on real market transactions or by the extrapolation of values from specific preferences. Economists’ interest in soil has traditionally been based on its agricultural value and the actual market value of crop production on that soil. Additionally, economic values have been assigned to loss of soil fertility and topsoil reduction.

 

More recently, economists and ecologists have developed an additional set of values based on ecosystem services soils provide (or fail to provide due to degradation.) These values reflect the increase in public welfare as a result of biodiversity maintenance, for example. This kind of non-market based value is more challenging to determine.

 

Some Midwestern farmers like Howard G. Buffett and his 28-year-old son promote a new soil-valuation system that reflects the true costs of erosion. They believe, as others do, that “if growers and investors had a more accurate index of soil quality, measured in real time, they’d have a heightened stake in preserving soil quality and quantity.”

 

Land capability

Land capability classifications are used to define best use of the soil resource. These systems are designed to put land into groupings based on their potential to provide some use to humans. By creating these categories soil scientists are creating a hierarchy of value for soil with respect to the ability it has to assist humans in their quest to survive by optimum exploitation of the resources available. The soil thus is defined by its value for a particular use and this value is obviously different to a farmer than an urbanite.

 

Degradation of the soil resource may include a decline of fertility and a deterioration of soil structure in addition to, or totally separate from, the loss of soil mass. All of these losses result in a decrease in capability and value for use. 

 

Geographic and cultural marginalization

Throughout history land acquisition has tended to move socially marginal populations onto ever more marginal land or off the land completely.  Some of this forced migration has been a result of soil quality and the desire to transform regions into uses that are perceived by governments to be of greater social benefit. During the height of European colonialism, residents of rich agricultural valleys in the global south were displaced to less productive uplands. The same type of cultural and physical marginalization has occurred throughout U.S. history.

 

In his Annual Report of the General of the U.S. Army in 1878, Sheridan stated that the Native Americans who roamed the plains were forced onto reservations with no compensation except promises which were never fulfilled. Now the population of Native Americans live in some of the most marginal regions of the country and experience high rates of poverty and the inability to make a living from the land.

 

The Great Migration (1914-1930) of African Americans resulted in the movement of black farmers off millions of acres of productive farmland so that between 1910 and the 1980s black ownership of farms had dropped by 80 percent (In 2007, there were 434 African-American farmers in California, farming about 8,000 acres)Between 1940 and 1970 migration of African Americans resulted in the transformation of a southern rural group to a northern urban one. 

When added to the inequality and marginalization of the poor by the wealthy, resource access and utilization is one-sided and the current needs of the rich outweigh the needs of the poor. In developing countries inequality fuels degradation and exploitation of local environments at the expense of ever more marginalized populations. The results of soil overuse and exhaustion are born disproportionately by the poor as they are forced to relinquish their land for a “higher use.” In the United States, entire races of people have been displaced off of high value land and now reside in areas where land use does not depend on soil productivity.

Current concerns regarding soils

 

GMO crops

There is interest surrounding the effects of transgenic crops on soils. The concern is that there may be deleterious effects on soils microbes and this has spurred research. The results of studies have been very diverse and seem to show that the effects of genetic modification on soils are crop-specific. 

 

Some research has looked at the effects of transgenic organic matter left in the soil, mycorhizzae and root exudates. Many soil scientists are concerned with a possible decrease in microbial diversity when GM crops are cultivated. Others are concerned with the transformation of diverse agro-ecosystems into monocropped, technology dependent systems and the long-term effects this transformation may have on the soil resource.

 

“Further consideration of the effects of a wide range of soil properties, including the amount of clay and its mineralogy, pH, soil structure, and soil organic matter, and variations in climatic conditions, under which transgenic crops may be grown, is needed in evaluating the impact of transgenic crops on soil nutrient transformations. Future environmental evaluation of the impact of the diverse transgenic crops under development could lead to an improved understanding of soil biological functions and processes."

 

Environmental degradation

The formation of soil is dependent on the materials soils are forming over (parent material), climate, biota, time and topography. An inch of topsoil can take as little as 200 years to form or may form over a more geologic time frame. It takes much less time to degrade or lose soil, as evidenced by the Dust Bowl.

 

At the time of the transformation of the American prairies, grazing herds were demolished, human inhabitants marginalized and the land was divided up among the new colonists. The rich topsoil and lack of trees allowed for easy clearance and excellent grain production. The abundance of roots made the topsoil especially high in organic matter and fertility (Topsoil is generally the top 6 inches of the soil profile. That’s where organic matter and many plant nutrients are stored. Many people regard soil as a renewable resource but once it has been removed or destroyed, it is essentially gone forever.)

 

On one hand, not many American consumers would agree that breaking up the North American prairie to establish the very successful and lucrative form of high technology agriculture currently practiced is land degradation. Yet, its establishment damaged the physical status of the natural system by breaking up soil aggregates and changing soil structure, the chemical status by removing essential nutrients and the biological status by removing native species.  In the eyes of a grassland ecologist, this agricultural use restricts the productive capacity of the prairie by reducing species diversity. But the American system of grassland agriculture practiced in the U.S. prairies produces high yields of corn and soybeans. And because of this benefit to society the destruction of a natural ecosystem and its replacement with a controlled, unnatural monoculture has been justified.

 

Management for the ecosystem

There are agricultural management systems that safely maintain the soil resource and others that assist in ecosystem diversity and improved environmental quality. Adding organic matter, keeping the soil covered, keeping the soil from moving downhill or up into the air through no- or low-till farming, terracing or contouring hill slopes are all ways to maintain the soil resource. Others farming systems mimic the native environment to maintain biodiversity and all of the benefits that go with it.

 

Adding organic matter may be the single most beneficial practice when it comes to soil conservation. Organic matter in the soil helps maintain and improve fertility.  It improves soil tilth and increases both water holding capacity and water infiltration. Having a living cover crop increases soil aggregation, a very desirable characteristic. Organic matter reduces compaction and crusting reducing runoff and erosion. It is also a source of carbon and when maintained can sequester carbon from the atmosphere.

 

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Carbon cycling and soil

Over the past 150 years the level of carbon in our atmosphere has increased by an estimated 30 percent. This increase has led to rising temperatures across the globe. One way to decrease CO2 in the atmosphere is to increase carbon storage in soils by increasing organic matter.  Soil organic matter (carbon) is depleted through the long-term extractive agricultural practices and the conversion of natural, diverse ecosystems into farmland. This kind of conversion depletes the pool of carbon in the soil by the simple breakdown of soil carbon to CO2 and a release of this gas into the atmosphere. 

 

To reverse this process, one thing land managers can do is add as much organic matter to the soil as possible. By doing this, carbon can again be “sequestered” in the soil. Keeping a crop on the soil by perennial cropping, leaving residue by no- or low-till farming or adding organic compost are all management practices that can increase carbon content in the soil. Using plants and soils to fix carbon in the soil is the only strategy that can actually remove carbon from the atmosphere and reduce the atmospheric concentration of CO2. This action is very different from cutting emissions which reduces the addition of CO2 to the air but does nothing to reduce the existing pool. As climate change causes more concern worldwide, sequestration of carbon becomes more important. Healthy soils enhance the earth’s natural ability to keep carbon from entering the atmosphere. 

 

As we proceed through the International Year of Soils we hope that this spot in the Rural California Report that we are holding apart will become a resource for discussion and education on the soil beneath our feet.