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Soil Erosion

Soil Moisture and Soil Erosion: What You Need to Know

Soil is formed partly from the effects of wind and rain. Throughout soil’s lifetime, it continues to be affected by the same elements. The effects of moisture on soil are determined by the moisture content for a given region and by taking into account the topography of the land. Current climate conditions have a significant impact on soil as land and sea temperatures continue to rise.

Erosion is a natural occurrence, yet when human-related activities (agriculture and development) change the structure of the land and therefore the soil, consequences take place. Determining whether an area is experiencing a drought or will experience one is measured by the soil’s moisture content. If the moisture content is too high, the risk of soil compaction rises. Soil that is dry or in arid climates may experience drought although that may change as climate does.

What Is Soil Moisture?

The level of moisture in the soil is often determined by variables in climate systems. Surface temperatures affect moisture levels through precipitation and evaporation. Drought and floods have severe impacts on soil moisture content in addition to the effects of climate change. As these conditions affect moisture content, they also indicate vulnerability to runoff and erosion.

Jamali Baruti, in a recent study of soil moisture in relation to soil erosion, explains: “Available water capacity (AWC) is the amount of water that the soil can store. It is the amount of water that is available for use by plants and is normally expressed as volume fractions or percentage.’ People have an adverse effect on soil’s AWC. Activities such as compacting soil with heavy equipment will decrease the amount of water soil can hold. Lower AWC makes soil more prone to drought.

Climate Change and Soil Moisture

The moisture content of soil has increased over the last 30 years: a trend that has coincided with rising temperatures due to climate change. As temperatures rise and rainfall increases, there is less chance for evaporation or for the soil to dry enough to lessen its water content.

Changes to the climate drive the global hydrologic cycle and intensify it. This cycle starts with oceanic evaporation that is lifted and cooled, then condensed into water vapor to forms clouds. Moisture is carried until it is deposited back to earth in the form of precipitation. As this cycle is disrupted, it opens the door for increases in ET or evapotranspiration which is the process of moisture up — then down — in the hydrologic cycle.

What Is Soil Erosion?

Soil erosion takes place when one or more contributing factors are in place, water not being the least. Soil erosion from water can be devastating as it strips the top layer of soil while diminishing the integrity of underlying soils. Debris and sediment are carried away and can change the soil’s composition resulting in loss of fertility or new plantings.

Soil Moisture and Erosion Combined

A combination of soil moisture and soil erosion can work to create a superlative amount of damage to an area. Erosion accounts for economic, environmental, and human health risks.

”Soil erosion rates vary widely over the landscapes, over a field and even along a slope profile within the field. To understand soil erosion over a particular area it is necessary to assess erosion at different landscapes for which various techniques are available,” says Mr. Baruti. 

Understanding moisture content is imperative to know what the health of the soil is at any given time and if steps can be taken to avoid drought or erosion. Testing soil for its moisture content with various soil moisture testing devices or techniques is recommended to minimize the impacts of erosion and moisture imbalances.

How to Test Soil Moisture

Gravimetric

By far the oldest method to measure soil moisture, the gravimetric process is lengthy and time-consuming. Soil samples are collected and weighed, then dried in an oven and weighed again, and compared for differences to estimated water content. The gravimetric method may prove difficult to apply if samples need to be taken from greater depths. Disruptions in the soil might also account for soil compromise as numerous samples might need to be collected for analysis.

Hand auger

These devices come with shaft extensions and are commonly used for deeper samples. Augers can be applied to depths up to 55 feet. The auger is turned by its handle which pushes its cylinder into the soil. The auger is then raised, and the cylinder’s barrel is emptied by striking it to free the sample. The gravimetric method can then be applied to the deeper sample.

Tensiometer

This device determines how much force a growing plant needs to absorb moisture from the soil. A tensiometer consists of a ceramic cup (porous point) connected to a measuring device. The cup is filled with water, and the water in the cup finds its balance with the soil. As the soil dries, water flows out of the cup to indicate greater tension. As soil becomes wet and its tension reduces, water flows back into the cup. Changes in these tensions are indicated on the instrument’s measuring device. Temperature can affect tensiometers as the gradients between the device’s porous point and the soil might cause variations in its measurements.

Moisture sensors or probes

Soil moisture sensors test for moisture volume through electrical resistance, dielectric constant, or through interactions with soil neutrons. These instruments run the spectrum from a low-end do-it-yourself type up to more sophisticated devices that can also measure soil pH and determine soil temperature. Simply insert the probe into the soil, and the instrument does the rest.

Soil erosion is a serious consequence of agriculture and development. A warming planet is disrupting its cycles to create balance in soil’s moisture content. As these imbalances increase or fail to stabilize, drought, runoff, or erosion might result.

Testing soil for its moisture volume is one way to find out what’s coming. Take measures to increase soil’s ability to infiltrate or drain to avoid conditions that contribute to adverse consequences. Working to prevent problems now can positively affect two important factors — agriculture and development.

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.

Erosion Effects on Soil Bacteria

The erosion of soils due to water or wind can disrupt a network of creatures invisible to the naked eye. These organisms work together to compose a fertile and complete soil. When land is stripped of its natural vegetation, its protection against erosion results in soil losing its ability to hold water and nutrients.

As organic matter is lost, farmers or landowners may add fertilizers, pesticides, and herbicides frequently or aggressively in an attempt to bring back soil harmony. Communities of microbes are also disturbed in the process of tilling soil and during erosion events. As the soil loses its working populations of microbes, pH levels may rise or free fall. Pest infestation is much more likely and nutrient availability is heavily impacted.

Why Does Soil Matter?

The formation of soil first happens beneath the uppermost visual layer where plant growth takes place. The soil might contain several layers or horizons, each of which contributes to the structure of the uppermost layer; the topsoil. Beneath the topsoil is subsoil that can be negatively impacted by erosion, especially when pH balance reaches below the surface to make the proper balance of nutrients and gases that much harder to achieve.

The topsoil, or what geoscience refers to as the A horizon, contains a myriad of organic matter that contributes to overall soil health and productivity. Soil is composed of rock, clay, or sand as well as plant and animal tissue going through the process of decomposition. This breakdown of material contributes to a thriving microbial community working together to balance and regenerate the soil’s make-up.

What Happens in Soil Erosion?

Agricultural land can experience rates of erosion 10 times the normal rate of loss. Approximately 1,500 feet of soil loss per 1 million years can be attributed to agriculture. While that may not seem like much, consider that the normal rate from natural erosion events is 60 feet of soil loss per 1 million years. Also considering that it takes thousands of years for soil to form and populate, the loss of half the world’s topsoil is a devastating consequence and one from which nature may struggle to rebound.

What Are Soil Microbes?

Soil is a living, moving substance that is home to different types of bacteria that contribute to the soil’s composition, nutrient availability, and recycling processes. These microbes are vital to soil health and aid in the breakdown of organic material like decaying plants and animals.

Microbes help to complete biochemical processes such as transforming nitrogen to a form usable by plants. Microbes contribute to the recycling of nutrients, thereby rebuilding the soil’s structure over and over again.

Soil contains aggregates that help protect its rate of decomposition. The National Resource Conservation Society defines soil aggregates as: “Soil aggregates are groups of soil particles that bind to each other more strongly than to adjacent particles. The space between the aggregates provides pore space for retention and exchange of air and water.”

Tilling land breaks down soil aggregates to compromise soil stability. As aggregates are crushed under heavy machinery, carbon might be released and soil microbes may overfeed on a now abundant energy source. As microbes feast, their normal rate of decomposition and recycling is disrupted. Once the feeding frenzy is finished, nutrients are not replaced and microbes die out once the food supply is exhausted. The living soil then becomes vulnerable to pests, inciting producers to turn to pesticides and other chemicals to restore balance.

Are There Different Types of Soil Microbes?

Microbes are the working group that continuously renews soil’s breakdown-rebuild process. They can be divided into sub-categories:

  • Micro-organism: Consists of soil bacteria, fungi, protozoa, and nematodes.
  • Mesofauna: Includes mites, springtails, proturans, and pauropods.
  • Macrofauna: These are in the form of earthworms and termites.

Soil microbes are generally comprised of these groups with most microbes taking on the role of decomposers. This group can consume simple carbon compounds while they break down pesticides and pollutants. Decomposers work to retain soil nutrients as well as prevent the loss of nutrients such as nitrogen. The rest might form partnerships with plants to exchange nutrients or contribute to the recycling of nitrogen and the degradation of pollutants.

As wind and water erosion strip away beneficial topsoil, biodiversity takes a hit and microbe populations suffer. Once these tiny organisms and beneficial bacteria are not in place to do their jobs, soil integrity is lost and will struggle to recover. Moreover, unhealthy soil can move and expand into other areas when it is left unprotected.

Steps to Aid Soil Recovery

Water and wind erosion can have serious effects on soil’s microbial health. As conditions for recovery continue to be assessed and evaluated, steps can be taken now to help minimize the effects of erosion on the soil’s hard-working microbial colony. 

Over-tilling soil and stripping the land of its protections put soil at risk. Replacing the vegetation that aids in feeding the soil’s microbes helps to counterbalance the loss of those tiny creatures. Bare land sets the stage for wind or water erosion and altering planting techniques (strip-farming, terracing, no-till) can lessen the disturbance of the soil. Using coir geotextiles can assist soil by holding it in place, keep it from drying out, or balance soil’s pH for a thriving microbe community.

Soil health is dependent on several factors and when one or more are imbalanced there is cause for concern. When microbe activity is disrupted or if its natural decomposition cycles are altered, soil quality suffers. Resulting issues of erosion, pH imbalance, and loss of soil fertility all adversely affect the soil’s ability to continue to produce.

Once the protection of soil is as big a priority as its use to grow and produce is, human activity can turn the man-made tide to encourage a thriving microbial community. Reducing damaging practices and adding natural textiles and plants can help curb erosion and hold soil in place. Earth’s upper layer is where we build and live. Protecting that layer encourages the soil to continues to produce and recover with the help of its microbial village. Time and space are critical components for these little guys to help soils convert food to energy, aid decomposition, and regenerate earth itself.

How is a Changing Climate Affecting Environmental Erosion?

The land’s ability to grow and produce food and shelter for the earth’s human population is at risk. Wind and water erosion contribute to massive amounts of soil and land losses while weakening the soil’s chances of recovering.

Human population growth and agricultural practices are taking their toll on soil’s ability to rebound and recover from erosion events. Native vegetation removed from land exposes soil to the elements and weakens its structure by impeding microbe populations. Bare land limits the abundance of nutrients that are normally returned to the soil through decomposition. 

Changes in temperature and precipitation affect soil health overall. Climate change plays a key role in weather events that create conditions for wind and water erosion. Because these conditions are primarily man-made, it will take man-made actions to reverse or minimize the damage. 

What is Climate?

There can be some confusion when referring to climate, going so far as interchanging the words climate and weather. While weather relates to immediate or day-to-day conditions (it’s snowing, or a storm is brewing), climate refers to an overall state of being. Climate is a compilation of weather events over a period of time and can illuminate patterns and inspire predictions. Changes in climate affect the soil’s ecosystem through changes in precipitation, temperature increases, plant growth rates, and loss of nutrient intake and uptake.  

Climate change refers to the acceleration of Earth’s natural cycles, how those changes impact weather events, and the planet’s overall health. Fossil fuel use, agriculture, and development all contribute to climate change and its effect on weather. As soil is compromised due to these changes in climate patterns and day-to-day weather cycles, its fertility is threatened, which in turn diminishes human efforts to grow food. 

How Does Climate Affect Soil?

Climate changes are affecting both temperature and precipitation cycles. As temperatures increase, precipitation changes. One example is when rainfall replaces snowfall. To remain stable and productive, soil must retain certain levels of moisture depending on its region. Precipitation is more than the amount of water that drops onto the soil; it also relates to how quickly water evaporates and returns to the atmosphere. Temperature and precipitation can contribute to soil moisture. However, if the process of pulling water back out of the soil, referred to as ET, or evapotranspiration, isn’t taking place, pH levels and microbial activity might degrade.

Soil requires many actions to maintain its vitality. As each component is impacted, soil struggles to recover and continue production. Loss of available land is directly related to soil erosion. Human activity contributes to soil losses 10 times faster than the rate of loss through natural erosion processes. China and India see their soil loss at more than 30 times the normal erosion rate.

How Does Climate Change Affect Erosion?

Because wind and water events dictate soil erosion, it is apparent that climate change directly affects the prevalence of erosion. Fall and winter are traditionally the end of the harvesting season and signal the onset of the rainy season. Bare land is more vulnerable to erosion during this period, as its protections are compromised. Crop covers are lower or nonexistent, and soil is unable to stay in place and resist runoff.

The Pacific Northwest’s Regional Approaches to Climate Change (REACCH) annual report states that, ‘Although warming results in an increase in rain and a decrease in snow water equivalent into late winter, soil losses are tempered. We hypothesize that this is due to the early onset of biomass growth caused by warming,”

Although this statement might indicate that climate change can have its advantages, the swap of rainfall for snowfall is not an advantage. Additional rainfall means an increase in precipitation. As more rain than snow falls, and because snow is less dense, rain accumulates at a faster rate and heightens the conditions for soil erosion. 

Soil and Climate Change

Soil is the basis for food and shelter, and the degradation of its health can lead to environmental, economic, and human health losses. Under current agricultural practices, tillage alone could increase the erosion rate from 0.17 tons per acre to 0.5 tons per acre, resulting in a 192% increase in soil loss.  

Erosion leads to the devastating loss of topsoils as well as a weakening of the underlying subsoils. Acidity accumulates in soil and trickles down to ultimately affect the O horizon — soil’s parent layer.

Controlling Erosion in the Face of Climate Change

By altering farming practices and replanting protective vegetation, we might be able to minimize climate change effects on soil and erosion loss. The use of coir textiles that help soil retain water and maintain pH levels while diverting erosion’s path prove to reduce loss, as well. Taking care not to compact wet soil or let it dry out contributes to a healthy microbial colony that aids in soil’s nutrient uptake, distribution, and regeneration.

The Geography Department at University of Kentucky College of Arts and Sciences offers a hopeful scenario: “There’s an obvious warning here with respect to ongoing and future climate change — relatively minor climate-driven disturbances could result in disproportionately severe erosion and land degradation. But there’s also an opportunity — in some situations relatively minor climate-driven disturbances in areas already experiencing erosion or degradation could be tipped into a minimum erosion, non-degrading state.”

It is not too late to recognize the effects of climate change and soil erosion. Committing to practices that help reduce instances of erosion or working to avoid it in the first place can have a positive impact on the land that is still able to work in human favor. As conditions change for better or worse, human interaction might be the first line of defense to man-made situations. 

When precautions are put into place and soil is given the chance to recover from previous seasons or harvests, the land might have an opportunity to bounce back and continue to produce. Stemming the effects of soil erosion is a crucial component for overall soil health and, ultimately, the health of the planet.

Human Contributions to Soil Erosion

Soil erosion is a serious consequence that affects the entire planet. Studies continue to support the fact that humans are the root cause of soil erosion, whether erosion occurs from wind or water. As the effects of erosion contribute to soil’s ability to produce and regenerate, soil quality continues to rapidly deplete. PH levels and nutrients are altered from erosion events and modern farming practices do little to offset these effects and often make it worse.

Population growth and agriculture are driving forces in the damage caused by erosion. As awareness grows, land management practices continue to evolve and search for solutions to mitigate erosion’s effects or work to prevent it from taking place.

What is Soil Erosion?

Soil erosion is the wearing away of soil layers from the effects of wind and water. Most soil erosion is caused by human activity, and agriculture and development are the primary drivers of wind and water erosion.

Wind erosion strips off topsoil and transports nutrients downwind while weakening soil’s stabilizing forces. The wind carries sediment over miles of land, leading to the exacerbation of allergies and upper respiratory conditions.

Soil erosion caused by water bombards soil with moisture it cannot absorb or resist. Topsoil and its nutrient layer might be carried away by a rain event, or soil’s pH and microbial colonies might be compromised.

Along with removing vital layers of fertile soil, wind and water erosion also carry away fertilizers, pesticides, and herbicides. Erosion carries and distributes these materials within sediment to incite environmental harm. 

Why is Soil So Important?

Soil might seem like a passive material but it is a living and evolving substance that is the heart of where we grow our food, construct our shelters, and practice our business. Earth’s soils are in a delicate balance and formed over millennia by forces of wind and rain and natural erosion events. The shaping of new soil depends on the area where it forms, which forces contribute, local microbes that make soil home, and soil’s ability to grow and produce. 

As the human population continues to inflate, agriculture land is increasingly at risk. Degradation of soil can render some areas unfit for production, leaving land vulnerable to excess erosion. Currently, soil’s ability to regenerate and replace what was lost is locked in an ongoing battle with population growth. In time, nature may not be able to keep up and land that is still able to produce may become less and less viable.

Human Soil Erosion Facts

When we take a closer look at the human impact on soil health and the part human activity plays in erosion, there come certain eventualities. In a 2006 Cornell University study on the effects of human activity and soil erosion, The Journal of the Environment, Development and Sustainability, stated the following facts.

  • Humans have been responsible for excess soil erosion since the first millennium.
  • Natural soil erosion occurs at a rate of 60 million feet per one million years.
  • Human activity accounts for ten times more soil erosion than all natural erosion processes combined.
  • China and India lose soil to erosion thirty times faster than natural occurrences, while the U.S. loses soil ten times faster.
  • In some agricultural areas, soil erosion rate is 1500 feet per one million years.
  • Worldwide, 37,000 square miles of cropland are lost each year to erosion.
  • Erosion has rendered 30% of the world’s croplands unproductive.
  • In the U.S., an estimated $37 billion is lost in agricultural production due to erosion and its effects.
  • Damage can exceed $400 billion per year worldwide.
  • Wind erosion transports airborne dust which can carry human infectious disease and pathogens, including tuberculosis and anthrax.
  • Some dessert soils have lost their entire A horizon or topsoil.

 What Human Activities Lead to Soil Erosion?

Agriculture and development are primary human practices that lead to or worsen soil erosion. As the consequences to infertile soil and climate change become more apparent, taking action to offset the effects of soil erosion is vital to maintaining land for agriculture. Fortunately, changes are taking place in the following areas.

Overgrazing: Farmers may have an overabundance of livestock. Sheep, cattle, and goats consume protective vegetation or compact the soil when they trod over it.

Overcropping. Crops constantly in rotation deny the land time to lay fallow and restore soil’s nutrients and balance pH. Soils dry out due to overcropping which leads to infertility. Farmers might compensate with excess fertilizers or artificial nutrients.

Deforestation: Clearing large land areas to harvest wood for construction or as a source of fuel leave those stripped lands bare and vulnerable. Removal of vegetation exposes land to water and wind erosion. Lack of reforestation can result in a loss of biodiversity, compromising soil structure and health.

Steps to Minimize Soil Erosion

Minimizing conditions that lead to soil erosion, as well as lessening impacts, may slake the damage. Planting crops with ample time between rotations can give the soil a chance to regenerate and repopulate with microbes and nutrients. Reduced soil tillage also has beneficial effects by lessening soil aggregate loss while reinforcing soil’s staying power.

Strip or terrace planting can help support soil in erosion events while providing nutrients and balancing pH. Using natural geotextiles help soil keep its moisture level in balance and provides nutrients to the soil. Replacing lost vegetation helps soil repopulate beneficial bacteria and regain their fertility and resilience.

Although extensive damage has already been done, steps can be taken to reduce the impact of wind and water erosion. Since human activity accounts for nearly all excessive erosion consequences, recognizing the role humans play and taking action to protect the planet and her growing layer of soils might mean the difference between a fed planet and a starving one.

Actions like altering farming practices to lessen land disturbance, planting natural vegetation and managing land so that the soil is protected and cared for. This results in lands that are able to produce because the soil is fertile and in balance so that it can work to human advantage, which is what we intended to begin with.