6 min
506 pplContents:
- Introduction
- Types of soil erosion
- What affects the intensity of the process?
- Possible consequences
- Control measures
The soil is a valuable natural resource since its condition influences the development of plants, a source of food for both people and animals. Therefore, it is so important to take measures to reduce its wind and water degradation. Otherwise, being deprived of fertile lands, humans fall into a direct dependence on technology and imports.
However, in the conditions of modern civilization, such a global problem as soil erosion is becoming more common. It is caused by natural and anthropogenic factors. In the former case, this is the influence of water and wind, slopes and mountains. Anthropogenic factors are caused by human activity: misuse of lands, deforestation, special methods of growing crops, construction of various buildings and infrastructure. Both processes lead to adverse and partially irreversible changes — decrease in fertility and damages to natural landscapes.
Today, the most erosive climatic zones in Russia are the Volga region, Western Siberia, Central Black Earth – here, the main reason is water erosion. The regions of the Far North, as well as the mountainous ones, also have this problem. The Black Earth and regions with a mild warm climate are considered less vulnerable to erosion. Nevertheless, certain features are noted throughout the country. According to experts, this can lead to an annual loss of up to 7 billion tons of fertile soil: dust storms damage up to 10 cm of humus layer, while it takes at least 100 years to form just 1 cm of it. Even today, about 5.4 million tons of nitrogen, 36 million tons of potassium and 1.8 million tons of phosphorus are being lost from fields and pastures. And in some zones, the rate of erosion of arable soil is 5–15 times higher than that of soil formation.
Erosion processes significantly impair the agronomic properties of the soil: they cause its compaction, reduce water-retaining qualities, and lead to the loss of clay and silt particles. This is evidenced by the data of the V.V. Dokuchaev Soil Science Institute: chernozem humus reserves have decreased by 250 t/ha over the past 70 years, water-retaining capacity has decreased by 600 t/ha, and yield has declined by 0.5 t/ha of dry grain per year.
All of this leads to surge in ravines, droughts and food shortages.
Types of Soil Erosion
Wind
It accounts for 1/3 of all soil erosion. It is observed on all cultivated lands. The wind scatters the top layer and carries the particles over long distances, which causes significant loss of the fertile layer. The intensity of wind erosion is determined by the frequency and speed of winds, the landscape diversity, and the soil type. It is most pronounced on terrains with no shrubs or forests.
Most often, wind erodes agricultural crops in early spring. Sprouts are unearthed, roots dry up, and the plants are covered in small particles of soil. What is more, fertilizer components and pesticide residues are also carried away.
Water
It is more insidious compared to the wind type — about 2/3 of all soil erosion is caused by rain and melt waters. They wash away the upper movable layer of the soil, which leads to the nutrient leaching. Most often, such processes are observed on cultivated hills and slopes. Falling drops of rain break the soil adhesion and carry its particles down. However, the intensity of water erosion largely depends on the type of crop grown, the amount of plant residues and the angle of slope.
Destruction of the soil layer by water can be:
- superficial — common in mountainous areas. Moisture is evenly distributed over the soil surface and erodes more than half of it, which harms crops drastically,
- rill — water flows contribute to the formation of rills,
- raindrop — typical for tropical and subtropical climates. Due to frequent heavy rains, the soil layer is deformed, its particles are gradually displaced forming cavities,
- irrigation — an anthropogenic factor caused by improper watering of the upper soil layer.
Combined
Under natural conditions, water and wind factors closely interact with each other. This combination leads to the global destruction of humus. The following schemes are possible:
- overwatered soil causes water runoffs, impoverishing and washing out of the fertile layer,
- erosion dries the soil with further soil blowing,
- snowmelt causes waterlogging and runoffs of melt water, which erode and dry the soil, which is then dispersed.
It is this "tandem" that leads to the formation of ravines that reduce the area of fertile land.
In this case, the speed of all erosive changes can be different. The normal speed is quite slow and hardly harmful to nature – even under the influence of wind, soil can be destroyed only in several millennia. The quick erosion speed does not allow the soil to recover, which damages the terrain drastically.
What affects the intensity of the process?
- Heavy rains 10–50 mm/h.
- Local topography – areas with slopes of more than 4%.
- Method of land use – unlike arable land, meadows, pastures and woodlands are less prone to erosion.
- Farming the fields along the slopes.
- Lack of boundaries when joining small plots.
- Deforestation.
The type of soil is also essential – those formed on loess and loose sand are prone to wind and water erosion more than others. Lack of vegetation cover and generally large flat areas lead to diminishing of soil fertility.
Possible Consequences
In the absence of preventive measures, erosion primarily leads to the exhaustion of the top layer. It is caused by pollution with mineral fertilizers, salinization due to irregular and uneven watering in arid areas, waterlogging and desertification, as well as uncontrolled use of agricultural machinery that damages and compacts the soil. The result is impoverishment of soil and a decrease in productivity, unsuitability for pastures and crops.
Erosive processes also lead to a decrease in the number and species of plants, which eventually turns the area into a desert. This is the main environmental problem as of today. Water bodies and rivers are also polluted: washed-out soil disrupts their ecosystem, contributing to the progression of fish and plant diseases.
Control Measures
One of the best ways to reduce soil erosion is to use overall vegetation and cultivate crops in erosion-preventing rotations. This involves the use of such mandatory components as winter crops — rye, rapeseed and triticale form a dense cover since autumn, as well as legumes in their pure form or combined with herbs. After early harvesting, catch crops or green manure should be sown, which are best left as mulch for the winter.
Conventional tillage practices involve plowing postharvest residues into a field, which leaves the soil unprotected and exposed to wind and water. In the case of winter and spring crops, the period of destructive effects of both types of erosion can be greatly reduced.
In addition to anti-erosion rotation, the following measures should be taken:
- Farming the fields across slopes, with mucking up the slopes.
- Loosening of the subsurface horizon, which increases water absorption.
- No-plow tillage instead of plowing. A cultivator with wide shovels is used.
- Cultivation of crops into mulch. Plant residues serve as a barrier protecting from the wind, scattering falling raindrops, fulfilling a function of a filter.
- Minimum pre-sowing treatments.
From the point of view of efficiency, mulch is the most acceptable variant demonstrating good results in soil erosion prevention. The so-called zero tillage, when plant residues cover field surfaces, helps to reduce the loss of fertile soil by 70–90%. The result depends on the uniformity of coverage, rather than on the bulk of vegetation.
It is also obligatory to plant new forest plots between fields and regularly care for the existing ones. It is important to introduce a crop-specific differentiated system for the use of mineral and organic fertilizers. Yield planning helps to prevent erosion. Cereal crops should be preferably seeded on the plains, while perennials — on the slopes. Pitting reduces outwashing, and soil slotting makes excess fluid accumulate in special slots.
