SoilErosion.com

Soil Erosion Problems and Solutions

Soil Education

The Ultimate Guide to Soil Horizons

Have you ever thought about the ground that’s beneath your feet and what is it composed of? We might think it’s just plain dirt, but scientists have determined that six different soil horizons make up the different soil profiles of the ground. Learn more about these soil horizons and what impact they can have on your gardening efforts.

What is a Soil Horizon?

Simply put, a soil horizon is a distinct layer in the ground. These six layers are made up of different substances that either look different, have different chemical makeups, or are physically different from the other layers. 

Soil horizons act as the history of the soil in a particular area. The layers are formed in a specific way due to the original composition of the land, the weather, the vegetation of the area, and other factors. Think of this as the biography of the soil.  

What are the Six Soil Horizons?

The six soil horizons are labeled with a letter denotation and are O, A, E, B, C, and R. Each of these soil horizon layers are unique. O is the soil horizon that is made up of organic materials. Soil horizon A is the layer that is made up of minerals. E is the soil horizon that’s comprised of eluviated soil, or soil layers that have gained materials from other layers by water movement. Soil horizon B is made up of subsoil. C is the soil horizon that contains parent material. Finally, R is the soil horizon that’s bedrock.

Soil Horizon O

Soil horizon O is made up of the organic matter or humus that falls on the soil. This organic matter has decomposed down and created a layer of soil. The O soil horizon can vary when it comes to the size of the segment.

Soil Horizon A

When you think of dirt, you probably imagine soil horizon A. It is the topsoil. It has a combination of organic matter and minerals located in it. Soil horizon A is the best for growing plants. It is always at the surface of the soil, as that is where it forms; however, it can show up again deeper in the layers. If there is a natural event, such as flooding or a landslide, that moves the ground, this layer can go deeper into the soil profile. This layer is often dark in color. 

Soil Horizon E

Soil horizon E is a complex layer that is mostly sand, quartz silt particles, and other material that can’t be leached away. It is formed by the organic materials, clay, and any minerals being leached out of the soil. Anything that can’t be leached out of the soil is left behind and makes up this layer. Soil horizon E is often found in forests and areas with old soil that hasn’t been disturbed in a long time. This layer is often lighter in color than other layers because much of it has leached into lower layers.

Soil Horizon B

Soil horizon B is the subsoil layer. All of the materials, such as minerals that are leached from the soil horizon A and E, make up this layer in the soil profile. Often, it has iron, soluble salts, and clay accumulated in it. Erosion can sometimes expose this layer to the surface, in addition to some manmade causes. Bulldozers and landscaping can also result in erosion that exposes it.

Soil Horizon C

Soil Horizon C is the parent material layer. The Earth’s surface deposits created this layer. It could have been produced by glaciers moving across the earth, lake sediment, or the exposure of bedrock. 

Soil Horizon R

Soil horizon R is made up of bedrock. The rocks typically found in this layer include limestone, quartzite, sandstone, basalt, and granite. In areas where the bedrock is exposed at the surface of the ground, these materials will weather. The materials that weather off of the bedrock become the soil horizon C. This horizon is technically not soil and is usually found under soil horizon C. 

Does All Soil Have All Six Soil Horizons?

There is no specific reason for soil horizons. Some soil profiles will have every single one of the six soil horizons in it. Other areas will have fewer soil horizons in their soil compositions. An example would be some may have just O, or O, E, and B, or A and C. In some spots, there may be soil horizons that repeat in different layers. An example here would be A, B, E, and B. Keep in mind that the majority of soil profiles will have A, B, and C horizons in them. Also, some may also include an O horizon in addition to these three major soil horizons. 

Not only can soil profiles have all six soil horizons, fewer than six soil horizons, or have repeating profiles, they can be found in any order. Soil horizons don’t have a set order for how the horizons appear in the soil profile. It all depends on how the soil was formed over time and the surrounding conditions.

Gardeners and Soil Horizons

Gardeners may not think too much about the soil horizons in their garden plots or the history of their soil, but it can help them to make informed decisions. Examining the soil horizons in the area you plan on planting can give you an idea of whether or not you may need to add some soil amendments to make the soil more fertile or to add loosen up soil that has a high clay content. Knowing your soil horizons can help you to determine what’s necessary to get your garden growing healthy and strong.

The soil horizons that make up your backyard may be exactly what you need to have a bountiful garden that doesn’t need much help. That scenario isn’t always what happens, so learning about soil horizons can be applied to your gardening efforts. Your garden soil will thank you with beautiful blooms and a nice harvest.    

Soil texture

Dig your hands down into the earth. What do you feel? Every handful of soil has its own individual texture, and those characteristics offer a significant contribution to crops. What determines the unique textures of soil? Why is it important, and which type of soil has more erosion resistance? Find the answers to these questions and more with this informative article.

What Is Soil Texture?

When a pedologist mentions ‘soil texture,’ they’re referring to the amount of various sized sand, clay, and silt particles in a sample of dirt. The composition of these grains makes up the inorganic parts of soil and are the bits and pieces that bind with organic matter to form topsoil.

The size of soil’s particles and their spacing also determines how much water will flow through it. Soil with a higher concentration of large grains of sand will have a greater infiltration rate, while dirt that is primarily clay will pool water on its surface as opposed to absorbing it.

Soil Textural Classes

A soil’s textural classification refers to the combination of sand, silt, and clay that make up the soil. It can be determined using exploratory research methods such as feel. A coarse-textured soil is probably composed primarily of sand, while a fine-textured soil is most commonly dominated by clay.

Farmers can also take a quantitative approach with a hydrometer. With this lab-based method, the soil is mixed with a sodium hexametaphosphate solution to separate the earth’s aggregates into identifiable parts. The U.S. Department of Agriculture outlines 12 primary soil texture classifications including the four most common types: sand, loam, silt, and clay.

Sand

Sand is the largest sized dirt particle. Each grain ranges in size from 2.0 mm down to 0.05 mm. It feels gritty to the touch. Since sand is just a bit of gravel, it drains well but doesn’t do an adequate job of retaining essential water and nutrients. Gravel particles that are larger than 2.0 mm are not considered when determining texture.

Loam

The soil that’s referred to as loam offers a proportion of 40% sand, 40% silt, and 20% clay in a single sample. It’s often the dirt of choice for making bricks and provides plenty of organic material for growing crops.

Silt

Silt particles are considered moderate in size. However, with sizes ranging from 0.05 mm down to 0.002 mm, individual particles are too small to see with the naked eye. It has a similar shape as sand particles, just worn down to a smooth texture.

While it’s not as strong as sand, silt is better at holding both water and nutrients. Because it’s prone to losing small amounts of minerals from each particle, silty soil generally makes more minerals available to your plants.

Clay

The smallest sized dirt particle, clay is less than 0.002 mm in diameter. To put that in perspective, you’ll need to line up 12,000 clay particles side by side to measure one inch. Clay feels sticky in your hands and is an excellent building medium.

What Determines the Texture of the Soil?

The percentage of materials determines a soil’s textural class, including the common particles we’ve already met: sand, silt, loam, and clay. Its texture is an important characteristic that influences a diverse number of properties, including water infiltration rates, aeration, susceptibility to erosion, and pH buffering capacity.

The Importance of Soil Texture

The texture of your field’s soil is essential to a successful harvest on a variety of levels. From saturation to water-holding capacity, let’s discuss each component of soil texture’s importance.

Infiltration

The amount of clay, sand, or silt in the dirt defines the rate at which water is able to drain through it. Once saturated, water moves more quickly through sandy soils than it does through soil that’s heavy in clay.

Availability

Soil texture influences how much water is available to your plants. Once your field’s saturation level reaches capacity, your clay soil will hold more water than its sandy counterpart.

Drainage

Well-drained fields are usually a sign of proper soil aeration. This texture of dirt is rich with air, which promotes a healthy root system and leads to a bumper crop.

Erosion

Different textured soils also respond differently to erosion. Some are more susceptible to loss based on their percentage of silt and clay particles. Those soils have a higher erodibility level than a sandy soil under the same weather and tilling conditions.

Organic Matter

Various soil textures also offer different levels of organic matter. This material breaks down faster in sandy soils than in silt and clay, likely due to the higher availability of oxygen for decomposition.

How Soil Texture Affects Erosion

Now we understand that a soil’s texture is directly related to the amount of clay, silt, and sand particles it contains. But what does this have to do with soil erosion? Soil texture has two main effects on erosion.

First, it influences the rate of infiltration and water’s ability to enter the soil. When it rains, does the water run off rapidly? If so, then you probably have sandy soil. This type of dirt has large pores that act like pipes, channeling water right into the ground.

Does the water collect on the surface or in low lying areas? If it does, then you probably have clay soils that are not known for providing good drainage.

Second, some types of dirt particles don’t detach as easily as others. Silt particles wash away easily because they’re tiny and don’t readily combine with other soil aggregates.

Which Type of Soil Is More Erosion Resistant?

One study suggests that an estimated 30 tons of agricultural soil are lost in the United States to erosion each year. This loss outpaces the rate of formation by an astonishing eight times.

So, which type of soil offers the most erosion resistance? The answer is clay. Clay is better at resisting erosion because it’s small particles hold water, making it a stickier compound than sand.

A soil’s texture affects many aspects of your garden, including erosion. Use this handy guide to help determine your dirt’s composition and how you can use that information to help you conserve topsoil.

Importance of soil

If you dug a hole 100 feet down into the ground, what would you discover? The first thing you’ll notice is that you’ve burrowed through many distinct layers of soil. Just what can you learn from this cross-section of earth waiting below the surface? Let’s take a closer look, explore the importance of soils, and see why dirt is crucial to all life on Earth.

Why Is Soil Important?

Soil is essential to life as we know it here on terra firma. It provides a place for plants to grow and a home for insects and fulfills other critical duties that our flourishing planet depends on, including the following:

A Medium to Grow Food

Soil is an essential component of plant growth. It supports their root systems, protects them from erosion, and keeps them growing upright. It also provides plants with essential minerals and nutrients, including water.

A Home for Many Organisms

A large variety of animals, insects, and other microbes live in soil and depend on it for food and air. It’s a diverse habitat for a wide range of organisms, such as worms and termites, that help break down organic matter and enrich the soil. It’s also a nesting ground used by many creatures to raise their next generation.

A Water Filtration System

Much of our planet’s rainfall and snowmelt flows to larger water bodies like streams and lakes, but much of it soaks into the ground. As it continues to seep through many layers of soil, it’s filtered clean of dust, chemicals, and other contaminants. This filtered water provides both plants and humans with one of the purest sources of liquid needed for good health and prime growth.

It Helps Maintain Atmospheric Gases

Dirt helps maintain adequate aeration and provides air to plant roots. By acting as a storehouse, layers of dirt help to regulate atmospheric carbon dioxide. Soil contains nearly twice as much carbon as the air, plus nitrogen and phosphorus. These nutrients are stored, transformed, and cycled into the ground.

Types of Soil

In the U.S., there are 12 classifications of soil textures. Here, we will discuss the four most common types, including the following:

Sandy Soils

Sandy soil has a gritty feel and warms up quickly in spring. It’s free draining and features large, hard particles, though it’s inferior at holding water.

Sand doesn’t bind very well with soil aggregates and it’s often low in nutrients because the nutrients wash away easily. The natural weathering of bedrock like limestone, shale, granite, and quartz produces sand.

Silty Soils

This type of soil has a fine, smooth texture and holds water better than sand. It makes a superior choice for crop cultivation because it holds more nutrients than course-particles. It’s heavier than sandy soils but not as heavy as clay. Silt forms when dust and fine debris are carried by water or ice and deposited on the ground.

Clay

Clay is made up of the smallest particles. They bind incredibly well, resulting in little or no breathing spaces for plants and insects. Clay is sticky when wet and easily molds into any form. When dry, it hardens into a rock. Soil that is rich in clay doesn’t drain very well at all and is thought to originate in the sediment of sea or lake bottoms.

Loam

Loam is a mixture of sand, clay, and silt particles. It’s high in the essential mineral calcium and retains water well. Most agriculturalists agree that loam is ideal for most crops. It’s a vegetable farmer’s top choice as it’s full of decomposed organic material and plenty of nutrients. These nutrients demonstrate why organic matter is important in soil. It also has a soft texture and is easy to cultivate.

Factors That Affect Soil Formation

The ground produces soil based on five factors. The interaction between parent material, time, climate, landscape, and the bounty of healthy organisms is what gives birth to new dirt.

Parent Material

Soil’s parent material refers to the minerals and organic matter from which it’s formed. It will retain its origin rock’s color, texture, structure, and mineral composition.

Time

It can take many years to break down parent material into dirt. As the land ages, new organic matter adds to the mix, and exposure to water and wind changes its features. As earth gets buried over time, it may evolve into a completely different type of soil.

Climate

Climate is often one of the most active factors that shape the formation of new soil. The two most critical climatic components are temperature and rainfall. A warm, damp climate means more vegetation and organic matter and the increased potential for water erosion.

Landscape

The landscape also plays a prominent role in soil formation. Water runs down steep, long slopes quickly, leaving behind poor quality soil on the hillside and an abundance of fertile land at the base. Expose these hills to direct sunlight, and these extreme conditions dry out the ground, making it less productive.

Uses of Soils

Much of the planet’s exposed surface has a covering of thick soil. It’s a precious ecosystem that offers mankind many useful applications.

Agriculture

According to the North Carolina Department of Agriculture, plants derive 13 essential nutrients from soil alone. It’s an excellent medium for growing food, as the roots use the dirt for strength and stability, too. Agriculture is definitely one of the most important functions of soil.

Building

From adobe covered structures to building blocks made of pure mud, soil has played an integral part in humanity’s building process for thousands of years. When compacted and dried, earthen bricks can support enormous loads. Providing shelter reveals yet more of the importance of soil.

Pottery

Clay is an essential component for making pottery. Even our ancestors knew that you just need to add water to this type of soil to create beautiful, functional ceramics. Clay is quite versatile, and once dry holds its shape indefinitely.

Health and Beauty Products

Soil’s microbes can be harmful to some strains of bacteria, which is why it’s commonly used to make antibiotics, ointments, and anti-cancer drugs. Even cosmetologists make beauty products from clay, including blush, foundation, facial masks, and toothpaste.

Soil is essential to all life on Earth. Its abundant supply takes years to replenish, and with so many varied uses, it’s conservation is important.

Everything You Need to Know About Soil Maps

Soil maps are an essential tool when it comes to land management. As knowledge about the environment grows, experts are learning that what is done in one area can have farther reaching impacts on the surrounding area. Mapping sustainable and unsustainable land for the long term is an excellent way to ensure proper planning, and the best way to move forward. Think of soil maps as a much larger version of testing the soil in your garden. Let’s deep dive into this topic and see how it can help your gardening efforts.

At the beginning of your growing season, most farmers and gardeners make the decision to test their soil. It’s important to determine whether or not you need to add fertilizer to your garden to provide your plants with the elements they need to grow strong and healthy. You don’t want to plant your garden with too much or not enough of a particular nutrient in the ground. In the long run, this practice could cause problems with your plants not performing as expected. 

What Are Soil Maps?

Think about how your backyard garden is set up. You may have several different types of soil to work with around the yard. For instance, you may not use the back portion because it has heavier clay soil, while the middle of your backyard has better soil for your garden’s vegetable plants. This soil is more conducive to successful gardening without requiring any changes, unlike the clay areas. On a smaller scale, when you test your garden soil, you’re creating your own soil map. 

The United States Department of Agriculture’s Natural Resources Conservation Service collects data and creates soil maps. They collect web soil survey data from throughout the country that examines the soil in detail. They then compile the web soil survey data into the soil maps. The maps will describe and classify the type of soil found in these areas. Soil-type maps can then help determine land management practices based on what dirt is located in that particular area.

How Are Soil Maps Made?

The USDA creates soil maps through a variety of means. They go out to the region they are mapping and compile data through physical field sampling and technology. They collect additional data through aerial photography and other sensing technology.

Technology has changed how the USDA maps the regions where they gather data. In the past, researchers had to use paper maps, cameras with film that needed to be developed, and topographic sheets to input their data. 

Now, they can use tablets that offer GPS and all of the map equipment they need on it. Their digital photos and other data can all be combined using the tablet, to create the soil map as they go along. An additional technological benefit is that in the past these surveys had to be printed. It could take years for the public to have access, which left the potential for the public to only have access to outdated information. That’s no longer the case with the use of tablets, computers, and online publishing. 

Information Included in the USDA Soil Survey

A USDA soil survey includes a wide variety of information that provides all of the data. It starts with an overview of the geography of the area, data about the major soil types, detailed pictures, and information on crops and plants located in the area. It also includes in-depth information on the soil, such as depth of the dirt, texture, and permeability.

Value of USDA Soil Survey Maps

To many, dirt is just dirt. The soil is so much more than that, though, as the qualities of the earth can differ from place to place. Land can have limitations and benefits that prompted experts to create a classification system for clay that’s called soil taxonomy. This taxonomy establishes a basis for the proper agricultural and engineering applications available for the soil that exists in a particular spot. 

Who Uses Soil Maps?

It may seem like soil maps aren’t something accessible for anyone outside of the US government but these maps are beneficial to other groups. Anyone can get access to the soil maps the USDA creates. The plans are available to the public and have a variety of uses. People can visit the Web Soil Survey site or WSS to access the data and create their own custom soil survey of the areas they choose.

What are Soil Maps Used For?

Developers and builders can use these maps to help in planning out their buildings. The structure of the soil can be crucial to whether or not the area can support development. The ground may be more beneficial for a particular type of construction, or it may show that building in that site isn’t advisable. 

Businesses that work with soil, such as farms and ranches, can use soil maps to determine where they should plant their fields or graze their livestock. They can use the information from the soil survey to determine if they should move their flocks to another area or if they should leave a particular field fallow. It can also help if they plan on expanding their farms with an additional property, to give them an idea of whether or not the soil in the area can support their plans.  

Even homeowners can benefit from using soil maps. The maps can help them when it comes to starting a garden, planting trees, picking out a new home, or even adding on to an existing home. The information can allow you to make an educated decision on matters that pertain to the land around you.

Whether it’s a prominent developer building a new shopping plaza or a homeowner trying to determine the best place in their backyard to grow vegetables, soil mapping is beneficial. The soil that’s under every building, park, farm, and place on earth has a story to tell. Soil maps make it possible to make the right decision for future soil planning on every level.  

Need to Know: Soil Degradation

The soil is a crucial component of agriculture and forestry, and degradation leads to a partial or total decline of its productive capacity. Due to natural hazards or human mismanagement, the soil can lose one or more of its potential ecological functions, leading to a steep decline in its capacity to be used in the production of goods and services.

Defining Soil Degradation

A 2004 report by the U.N. Department of Economic and Social Affairs described soil degradation as a process that occurs when “the balance between the attacking forces of climate and the natural resistance of the terrain against these forces has been broken by human intervention, resulting in a decreased current and/or future capacity of soil to support life”.

Soil degradation is primarily attributed to mismanagement or misuse of the land in domains such as agriculture, industry, or urban planning. Due to its major impact on food growth and consumption and on the environment as a whole, soil degradation causes have been a constant topic of research and concern throughout the 20th and the 21st centuries.

Causes of Soil Degradation

Throughout the world, soil degradation is usually caused by one or more of these three factors:

  • Physical factors represent the loss of the soil’s life-sustaining qualities due to natural physical forces, mainly water or wind erosion. These physical forces affect the structure of the soil mainly by damaging its top layer and subsequent organic matter, where the nutrients necessary for sustaining growth are found. Long-term exposure to massive rainfall, winds, floods, surface runoff, or any other powerful physical factors leads to the slow decline in the respective soil’s structure and quality. According to Volume 11 of the publication “Advances in Soil Science,” physical degradation can include:
    • Compaction and hardsetting, causing densification of soil due to the elimination or reduction of its structural pores, and also increasing soil’s bulk density as a result of natural and manmade factors.
    • Desertification caused by erosion and sedimentation due to constant exposure to wind and water.
    • Laterization, meaning the desiccation and hardening of plinthitic material.
  • Chemical factors are the alterations of the soil’s chemical properties that lead to it losing nutrients. University of Chittagong professor Khan Towhid Osman’s book, “Soil Degradation, Conservation and Remediation,” states that chemical degradation of soil can be caused by a number of factors, such as a rise of alkalinity or acidity levels, or simply the oversaturation of the respective soil with water. The result is usually either a buildup of salt or the hardening of the soil, with soil nutrients being irreversibly lost in the process. More than half a billion acres of land are affected by chemical soil erosion throughout the world. 
  • Biological factors refer to human activities or plant growth that cause degradation of soil quality by accentuation compaction, erosion, water runoff, anaerobiosis, nutrient depletion, reduction in SOC pool etc., as described in the book “Soil Degradation in the United States: Extent, Severity, and Trends.” An overaccumulation of fungi or bacteria can, for example, cause biochemical reactions that will drastically reduce the soil’s capacity to grow proper crops. Poor farming practices and overfarming also have the potential to diminish the fertility of the soil by depleting it of nutrients. These farming practices can be excessive cultivation, improper manuring, misuse or overuse of fertilizers, or excessive irrigation, among others. 

There are also other factors that can lead to soil degradation. Deforestation will dramatically alter the soil’s composition by removing the vegetation that binds it together. Mining and other industrial activities release toxic substances into the soil, making it poisonous and completely unusable. Also, urbanization will unavoidably affect the soil quality by covering the soil with concrete and with the inevitable rise in pollution levels.

Effects of Soil Degradation

The most significant effect of soil degradation is the loss of a land’s life-sustaining qualities. Throughout the world, more and more land becomes unusable because of factors like soil pollution, contamination, and erosion.

The overuse of fertilizers also keeps the affected land from regenerating, polluting both the land and water in the area and dramatically decreasing land value.

Another major effect of degradation to the soil is its contribution to droughts and the occurrence of arid conditions in certain areas. Soil degradation reduces the biodiversity in the area, leading to desertification and the inevitable drought and aridity that come with it.

The University of Sheffield’s Grantham Centre for Sustainable Futures estimates that approximately 40 percent of the world’s agricultural land is unusable because of the loss of soil quality caused by degradation and overuse of agrochemicals. These practices make agriculture impossible, and therefore make the respective land useless.

Due to the alteration of the degraded soil’s physical attributes, one of the consequences is the affected land’s inability to hold massive amounts of water, leading to increased chances of floods occurring.

How Big is the Range of Soil Degradation Observed Between Continents?

Soil degradation is a big issue all over the world, but Africa is by far the most-affected continent. Throughout the African continent, it is estimated that 28 percent of the land is affected by degradation.

This costs the continent as much as 56 billion euros every year. It’s usually manmade, with the lack of fertile land being compensated by mass deforestation, leading to massive soil degradation. It can be reversed, though, with massive state programs and policies that train communities to take better care of the land. 

Other areas of the world gravely affected by the degradation of soil are Southeast Asia, Northern and Central Australia, China, and parts of the boreal forests in North America and Siberia. 

Solutions for Soil Degradation

The reduction and reversal of soil degradation typically lie in the elimination of manmade causes. Chief among these causes is massive deforestation, and the trend can be reversed by educating populations and governments about the dangers of reckless deforestation. Improving the land’s organic composition and restoring its mineral matter can also reverse soil degradation.

Prevention is also crucial to reducing the amount of land that is affected by soil degradation. Reducing over-irrigation, improving overall irrigation efficiency, and preventing land salinization are all significantly more cost-effective than restoring soil that has already been affected by degradation.

Soil degradation is an issue that affects the entire world in numerous ways. It increases the odds of famine and poverty in already impoverished countries. It also increases the cost and human labor that’s necessary to grow food throughout the world, massively influencing the price and quality of the food that we eat.

Other side effects, from dramatic rises in pollution levels to socio-economic effects like mass migration, also contribute to soil degradation’s status as a major global issue.

Sources:

Advances in Soil Science Vol. 11, Soil Degradation

Soil Degradation, Conservation, and Remediation, Khan Towhid Osman

Soil Degradation in the United States: Extent, Severity, and Trends, Rattan Lal, Terry M. Sobiecki, Thomas Iivari, John M. Kimble