Soil Erosion

Soil erosion: An agricultural production challenge

 

Soil erosion is a gradual process that occurs when the impact of water or wind detaches and removes soil particles, causing the soil to deteriorate. Soil deterioration and low water quality due to erosion and surface runoff have become severe problems worldwide. The problem may become so severe that the land can no longer be cultivated and must be abandoned. Many agricultural civilizations have declined due to land and natural resource mismanagement, and the history of such civilizations is a good reminder to protect our natural resources.

Erosion is a serious problem for productive agricultural land and for water quality concerns. Controlling the sediment must be an integral part of any soil management system to improve water and soil quality. Eroded topsoil can be transported by wind or water into streams and other waterways. Sediment is a product of land erosion and derives largely from sheet and rill erosion from upland areas, and to a lesser degree, from cyclic erosion activity in gullies and drainageways.

The impact of soil erosion on water quality becomes significant, particularly as soil surface runoff. Sediment production and soil erosion are closely related. Therefore, the most effective way to minimize sediment production is the stabilization of the sediment source by controlling erosion. Several conservation practices can be used to control erosion but first you need to understand the factors affecting soil erosion. Soil erosion is the detachment and movement of soil particles from the point of origination through the action of water or wind. Thus, minimizing the impact of water or wind forces is the main objective for erosion control. Water erosion is the most pertinent erosion problem in Iowa.

Soil erosion by water occurs when bare-sloped soil surface is exposed to rainfall, and the rainfall intensity exceeds the rate of soil intake, or infiltration rate, leading to soil-surface runoff. Soil erosion can occur in two stages: 1) detachment of soil particles by raindrop impact, splash, or flowing water; and 2) transport of detached particles by splash or flowing water. Therefore, soil erosion is a physical process requiring energy, and its control requires certain measures to dissipate this energy.

The hydrologic processes of rainfall and runoff play an essential role in water erosion. The amount and rate of surface runoff can affect erosion and sediment transport. Thus, soil conservation practices are important in reducing soil erosion. Improving the soil infiltration rate, resulting in less surface runoff, can lead to reduction of soil erosion. Agronomic, cultural, or structural practices are available for controlling soil erosion. Structural practices involve physical changes in the shape and topography of the land. All these practices are not mutually exclusive. Some situations may require both management and structural changes, where the topography is highly complex. In other situations, erosion control can be achieved by implementing a single practice, where the erosion is minimum, such as the establishment of grassed waterways.

Types of Erosion Sheet erosion (water) is almost invisible. Lighter colored soils are a sign that over the years erosion has taken its toll. Wind erosion is highly visible. Although it is a problem, water erosion is generally much more severe. Rill erosion occurs during heavy rains, when small rills form over an entire hillside, making farming difficult. Gully erosion makes gullies, some of them huge, impossible to cross with farm machinery. Ephemeral erosion occurs in natural depressions. It differs from gully erosion in that the area can be crossed by farm equipment.

 

 

The most effective way to control erosion is to maintain a permanent surface cover on the soil surface, such as pasture or meadow. Therefore, areas that are highly susceptible to water or wind erosion need to be considered for soil conservation programs. Soil losses in Iowa due to water erosion and surface runoff can contribute a great deal to surface water quality concerns.

Many studies indicate that soil erosion results in large decreases in soil productivity. In a study conducted at Iowa State University on 40 soil associations, Craft and coworkers (Proceedings of the National Symposium on Erosion and Soil Productivity, 1984) reported that the impact of soil erosion on soil productivity was largely determined by subsoil properties because they effect root growth, soil water availability, and plow layer fertility. Thus, the loss of the topsoil can have considerable impact on yield, where nutrient availability, root growth environment, and soil water availability are essential for plant development. In soils with unfavorable subsoil conditions, erosion can have a large effect on productivity, if the plow layer soil fertility is not restored.

Plant residue management is another way of controlling soil erosion by intercepting raindrops, thereby reducing surface runoff and protecting soil surface particle detachment by raindrop impact. Crop residue can provide an excellent soil cover after harvest and enhance snow harvesting during the off season, improve soil water intake by preventing soil surface sealing due to raindrop impact, and consequently, reduce surface runoff. Equally important in minimizing soil erosion is the adoption of a cropping system along with conservation tillage practices such as no-till, strip-till, and ridge-till. The degree of effectiveness of different tillage practices depends on the degree of soil manipulation, which effects the residue distribution on the soil surface. Table 1 shows combinations of different cropping systems and the relative scale of erosion hazard associated with each system.

Table 1. Relative erosion hazards of selected cropping systems.

Cropping System Hazard	Relative Erosion
Fallow	244
C-Sb	120
C-C-Sb	112
Continuous corn	100
C-C-C-Ox	73
C-C-Ox	68
C-Ox	59
C-C-C-O-M	46
C-C-O-M	32
C-C-O-M-M	27
C-C-O-M-M-M	22
C-O-M	17
C-O-M-M	12
C-O-M-M-M	10
C-O-M-M-M	9
Continuous cover	0

C, corn; Sb, Soybean; O, oats; Ox, oats with green manure crop; M, meadow.

Causes Of Soil Erosion: Why Does It Happen?

There are natural and anthropogenic factors. Topsoil in fields is taken away by winds or quick water run-offs during heavy rainfalls. However, there is also the erosion of soil caused by farming itself when it is managed poorly.

Natural Factors Of Soil Erosion

• Strong wind gusts. Heavy winds remove dry tiny earth particles, which is a typical problem in semi-arid regions leading to desertification.
• Climate change. Abnormal rainfalls or temperature leaps destroy the field surface. Another effect of climate change on soil erosion is stunted vegetation growth that reduces field cover and exposes it to rains and winds.
• Rainfall and Flooding. Excessive rains wash away topsoil particles, while large raindrops hit the field surface and destroy it with heavy splashes. Running currents during floods is another cause of soil erosion.
• Wildfires. Trees and shrubs slow down water run-offs. When forests or buffer zones are destroyed by wildfires, water streams have no obstacles in their way.

Soil Erosion By Human Activities

Apart from natural factors, soil erosion occurs due to irresponsible farm management or deforestation for urban area expansion, tourism development, road construction, and more.

Farming Practices That Cause Soil Erosion

Natural vegetation is by far better protection than crops because farmlands are more vulnerable to rainfall and winds. Besides, agricultural practices can cause soil erosion due to a reduction of biodiversity both in vegetation variety and soil microorganisms. In its turn, a lack of organic matter and beneficial biota negatively impacts field fertility because not only earth particles but nutrients are taken away from bare fields.

The primary causes of soil erosion due to poor farm management are excessive fertilization or irrigation, conventional tillage, monocropping, overgrazing, and more. Let’s consider the impact of the separate farming practices on erosive processes.

Does monocropping cause soil erosion? Monocropping, or monoculture, implies growing the same crop for several seasons. Since each crop requires particular nutrients, this practice causes field depletion. Consequently, it may result in land degradation and soil erosion.

Can conventional tillage cause erosion in fields? It can. In particular, moldboard plowing makes the earth loose contributing to agricultural soil erosion by water and winds. Conversely, no-till farming prevents these processes.

Do fertilizers cause soil erosion? It may happen. Excessive use of mineral fertilizers under insufficient organic fertilization leads to dehumidification and destruction of its structure, which in turn makes it more vulnerable to erosive processes.

Does irrigation cause soil erosion? Sometimes it can. Artificial irrigation is the only way to produce crops under a lacking natural water supply but excessive irrigation can cause topsoil erosion. It particularly refers to surface irrigation when nutrients and topsoil particles are removed from uneven fields due to gravity.

Does overgrazing cause soil erosion? It does. Livestock overgrazing is a vivid example of poor pasture management that destroys topsoil cover promoting erosive processes. Rotational grazing and cover crops can solve the problem.

Does terrace farming cause soil erosion? It doesn’t. On the contrary, terrace farming prevents erosion by slowing down water streams on even platforms.

Erosion Of Soil Caused By Logging And Deforestation

Any tree felling can speed up erosive processes, be it timber harvesting or expansion of agricultural lands for oil palm cultivation. The clear-cutting practice, when all or most of the trees are removed, exposes the forestlands most.

Does deforestation increase soil erosion? Yes, it makes forestlands more prone to erosive processes because trees:

• cast a shadow to protect its surface from drying out;
• fix the forestland with roots;
• slow down water run-offs;
• enrich the forest floor with organic matter.

Types Of Soil Erosion

The classification is based on the speed of the erosive process or its cause (agent). Thus, different types of soil erosion fall into accelerated or gradual, anthropogenic or natural. The main agents of soil erosion due to natural factors are water currents and wind storms, yet the situation may be aggravated by human activities as well.

Water Erosion

As the name suggests, this soil erosion type is caused by water and implies topsoil removal after rainfall, snowmelt, floods, or poorly managed irrigation. Thus, it can occur both due to weather extremities or farming activities. In bare terrains and under intense rainfall or melting, destruction by water happens faster.

The main types of soil erosion by water are bank, sheet, rill, gully, and splash ones. See their detailed description in our “Water Erosion: Types, Causes, Effects, And Prevention” article.

Wind Erosion

Another erosion-inducing factor is dust storms destroying the topsoil. Dust storms have been a frequent phenomenon in the last decades, especially in arid places. Erodibility increases if the earth is even, fine, and dry. Conversely, ridges reduce wind energy, and rough heavy particles are more difficult to be removed.

Anthropogenic Soil Erosion

This type occurs due to anthropogenic factors, and human activities can induce soil erosion directly and indirectly. For example, a direct impact comes from mining and quarrying. Indirect consequences follow unsustainable management, disturbing the topsoil and increasing erodibility of fields and forest stands.

Effects Of Soil Erosion

Erosive processes impact farming productivity, worsening living standards and well-being of rural communities (both individual farmers and agricultural co-ops). Over time, eroded farmlands lose soil fertility, degrade, and become unsuitable for agricultural activities.

Environmental Impact Of Soil Erosion

Negative consequences for agriculture are not the only nuisance. Examples of damage caused by soil erosion are decay in aquatic inhabitants and plants, biodiversity loss, sedimentation, and frequent flooding.

Frequent Flooding Events

When forests are converted into pastures or fields, there is always a risk of frequent flooding because the trees’ roots fix the land. Such areas also lose their infiltration properties, which also contributes to flooding and waterlogging.

Clogged Waterways And Polluted Aquatics

Long-term effects of soil erosion include waterway clogging and siltation. Besides, eroded particles not only produce sedimentation in evener areas but clog grassed waterways, dams, and water pumps. Quite often, water currents from fields contain chemicals that are dangerous for people and animals and poison drinking water.

Loss Of Biodiversity

Eroded lands have sparse vegetation and become completely bare over time. It means not only decay in local flora but fauna as well because many organisms are deprived of their natural habitats. The loss of biodiversity results in ecosystem imbalance.

Reduced Greenhouse Gases Sequestration

Vegetation and trees are great carbon dioxide storage, but eroded lands can hardly support their growth. Besides, soils also can also act as CO2 sinks themselves . According to Professor Peter Smith from Aberdeen University, the earth can keep nearly 5% of anthropogenic greenhouse gases per year. Sustainable management could improve the situation and stop the loss of carbon-sequestering vegetation on our planet, reducing greenhouse gases released by deforestation.

Solutions To Soil Erosion

Decision-making in soil erosion control depends on factors like the soil type, topography, or climate specifics, and applied agricultural practices like tillage system or crop rotation. It is important to analyze the effectiveness of undertaken methods and adjust them for individual fields.

Success starts with early problem detection and the choice of suitable methods depending on its severity. For example, replanting, cover crops, or mulching can be good ways to reduce soil erosion in the initial stages because vegetation protects fields from destruction by water run-offs, raindrops, and wind. In severe cases, the impact can be mitigated with terrace farming or check dams.

Other soil erosion control measures include contour cropping and planting perennials with strong root systems to fix the ground and slow down water streams.

How To Prevent Soil Erosion

It’s not that easy to reduce erosive processes and even more difficult to stop them, this is why prevention is by far the best method of control.

Produce Crops On Suitable Lands

Some terrains are extremely prone to erosive processes, so they can’t be used for farming without certain preventive measures to mitigate the risks. Besides, each field type requires specific management to protect soil from erosion.

Practice Terracing And Contour Farming

Because erosion develops fast due to quick run-offs, terrace farming is the only way to grow crops on steep hills. Contour farming decreases soil erosion because plants absorb water and ridges stop it from flowing, which mitigates the destruction risks. Plants with strong roots also fix the land and prevent it from sliding down the slope.

Don’t Leave The Soil Bare

Field cover helps not only reduce but prevent field destruction. Over 30%  ground cover for erosion control helps essentially mitigate the risks. Complete cover can be practiced in most grazing and crop production systems.

Plant Vegetation

Planting crops help prevent soil erosion by ensuring continuous ground cover, while leaving the field bare promotes erosive processes. Provide soil cover in between the growing season with crop rotation and cover crop practices. Besides, crop rotation reduces soil erosion by fixing the land with alternatively planted deep-rooted crops. Additionally, sequences of high vegetation protect fields from the wind.

Use Mulching

Mulches like straw, dried weeds, or agro textiles don’t only protect the field from rains and wind but retain soil moisture, which protects the earth from cracking. Besides, decomposed mulches of biological origin add nutrients and organic matter to the field, boosting fertility and improving its structure.

Switch To No-Till Or Minimum Tillage

Plowing is a common practice in conventional farming, yet studies prove that the reduction of farmland disturbance  in the no-till approach can help reduce soil erosion, too. When soil aggregates and ground cover remain nearly untouched, erosive processes develop slowly.

Add Organic Matter

Healthy topsoil must contain organic matter from decomposed animal manure and plant manure. Organic matter prevents soil erosion in several ways:

• supplies vital nutrients to crops making the ground cover more vigorous;
• improves water retention properties and decreases run-offs;
• binds the earth particles to help it resist currents and winds.

Use Rotational Grazing

When livestock grazes in the same place for a long time, it eats up nearly all vegetation. In turn, ground cover loss often provokes erosion. This is why it is important to let the grazed areas regenerate by moving the cattle to other pastures.

Switch To Drip Irrigation

Because dripping excludes excessive water flows and splashes, it is the best irrigation method used to prevent soil erosion. Dripping systems supply tiny water drops to plant roots at the surface or underground without any destruction risks.

EOSDA Crop Monitoring To Facilitate Prevention And Identification Of Soil Erosion Processes

There are different ways to reduce soil erosion, depending on its type and field specifics. It is typically recommended to use conservation agriculture techniques and sustainable farming practices. By applying modern technologies, growers can enhance the effect of anti-erosion tillage. In terms of soil erosion, remote sensing tools are excellent for monitoring large agricultural areas and can be used by both “big players” of the agricultural sector and small-scale farmers. EOSDA Crop Monitoring is an example of the application of GIS in soil erosion control.

Variable-Rate Fertilizer Application

As defined above, the improper use of certain agrochemicals can provoke wind or water erosion. Soil erosion on cropland often occurs due to excessive mineral fertilization in the absence of an adequate amount of organic fertilizers. Such an approach leads to field dehumification and destruction of its structure. Fields with low humus content are more susceptible to soil erosion, as small non-aggregated soil particles are more easily washed away by water or displaced by the wind. Nonetheless, these negative consequences can be avoided with a rational distribution of mineral and organic fertilizers, facilitated by Variable Rate Application technology.
The Zoning feature in EOSDA Crop Monitoring helps understand the required amounts of mineral and organic fertilizers for different areas depending on their individual needs. By using this feature, farmers can divide their fields into several zones based on vegetation indices maps. Each zone on the map shows certain vegetation intensity, assisting in fertilizer distribution for each zone.

EOSDA Crop Monitoring zoning feature for smart fertilizer application.

Excessive use of mineral fertilizers results in nutrients leaching from the soil profile, chemical pollution, crop intoxication, and a field productivity decrease. On the other hand, rational application will not only save growers’ costs by reducing the amounts of necessary resources but positively affect the environment, also assisting in the control of soil erosion.

Crop Rotation Planning And Monitoring

Crop rotation is among the key farming practices to reduce soil erosion. Depending on the slope steepness and already existing erosion manifestations, one or another type of crop rotation is applied, including the vegetative control of soil erosion with perennial grasses. Also, crop rotation is considered an important factor in maintaining high field productivity, since constant cultivation of the same monoculture depletes the field, leading to soil sickness and toxicity.

EOSDA Crop Monitoring functionalities allow for convenient crop rotation tracking in separate fields. The platform users also can add a crop rotation history for each new field for easy tracking and planning of further actions. To do so, just specify the sowing and harvesting dates and the crop name. The added data for each field simplifies the crop sequence planning for the next growing seasons depending on field productivity and needs. Basic crop rotation rules, along with other recommendations, help prevent a decrease in field productivity and the development of soil erosion processes.

Historical data about crop rotation in a field stored in EOSDA Crop Monitoring.

Field Productivity Monitoring

EOSDA Crop Monitoring highlights the current field state with various vegetation indices. Regular satellite imagery updates provide actual information on the crops. Also, the platform users can access historical data on vegetation state changes. With historical data for several years, you can create productivity maps that are generated with cloudless imagery analytics for the selected period.

When comparing productivity maps for different periods, growers can also trace changes in the level of vegetation in the entire field or in its individual zones. Soil erosion mechanisms are one of the reasons for a vegetation level decrease. Once a change is detected, it will make sense to additionally inspect the field and perform soil testing, to understand the cause of vegetation decay, and confirm or exclude the effects of soil erosion on crop productivity.

Refernces

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By -

Rokade Nishant
(B.ed. First year 2023-24)