Soil Fertility, Degradation, and Conservation

Historical Development of the Concept: From Dokuchaev to the Present

The understanding of fertility has undergone a long evolution. Let's trace the main milestones.

1. Pre-scientific Period: Empirical Agriculture

For millennia, farmers knew that some lands were "good" and others "bad." They applied manure, ash, left fields fallow, but had no scientific explanation for why it worked. Fertility was perceived as a given, mysterious property of the land.

2. V.V. Dokuchaev: Fertility as a Consequence of Soil Formation

In the late 19th century, the great Russian scientist Vasily Vasilyevich Dokuchaev revolutionized earth science. He proved that soil is an independent natural body, formed through the complex interaction of five factors: parent material, climate, topography, living organisms, and time. Dokuchaev showed that fertility is not an innate quality of the rock, but the result of a long-term soil-forming process. It is in this process that organic matter, nutrients, and a favorable structure accumulate in the upper layers of rocks.

"Since all the most important soil-formers are distributed on the earth's surface in the form of belts or zones... it is inevitable that soils should also be distributed zonally" (V.V. Dokuchaev, cited in Mukha et al., 2003, p. 196).

This concept of soil zonality laid the foundation for understanding why the fertility of different soils naturally differs.

3. Fertility as "Capability": From Statics to Dynamics

In the 20th century, a classical definition emerged, which we find in fundamental works: "Soil fertility is the status of the soil with respect to its ability to supply the elements essential for plant growth without toxic concentration of any element" (Foth & Ellis, 1997, p. 1).

Note the key points of this definition, which are still relevant today:

• Ability to supply—that is, not just to contain, but to give.
• Essential elements—a balanced set of macro- and micronutrients.
• Without toxic concentration—fertility implies not only sufficiency but also the absence of harmful substances.

However, this definition, for all its precision, did not reflect the full complexity of the phenomenon. Further scientific development showed that fertility cannot be reduced to chemistry alone.

4. V.R. Williams and the "Law of Return": The Agronomic View

V.R. Williams, the creator of the grassland farming system doctrine, emphasized the inextricable link between fertility and biological processes. He focused on the role of perennial grasses and structural aggregates. His ideas on the necessity of returning nutrients to the soil formed the basis of the law of return—one of the fundamental laws of agriculture, which states that to maintain fertility, it is necessary to compensate for the removal of nutrients with the harvest (Mukha et al., 2003, p. 191).

5. Modern Systems Approach: Fertility as an Integrative Function

Today, we view fertility much more broadly. It is not just a "box of fertilizers" but an integrative property of the soil as an ecosystem. In the modern understanding, fertility is the ability of the soil, as a component of the biosphere, to provide the terrestrial factors and conditions necessary for plant life, determining the nutrient, water-air, thermal, redox, and other regimes (Mukha et al., 2003, p. 184).

The key point here is the ecosystem approach. We are moving from understanding soil as a passive substrate to understanding it as an active, living system, where properties and regimes (not only chemical but also physical and biological) are in constant interaction.

Why is Fertility a Property of Soil, Not Plants?

This question is crucial for delineating our subject—soil science—from agrochemistry and plant physiology.

Fertility is potential, not result.

Let's recall the classic image: soil is a "storehouse", and plants are "consumers". Fertility is a characteristic of the storehouse itself: its size, fullness, preservation, and ease of access. Plants, using this potential, create a yield.

In soil science, the concepts of "potential" and "effective" fertility are used for this (Foth & Ellis, 1997).

• Potential fertility—is the natural reserve accumulated in the soil over a long period of soil formation. It is determined by the reserves of humus, nutrients, and the physical properties of the soil. It is like the soil's capital.
• Effective fertility—is the degree to which this potential is used by plants under specific conditions. It depends not only on the soil but also on technology, weather, and the plant itself. It is like the income from the capital.

Valkov et al. (2004) emphasize that fertility is "the ability to ensure plant growth and productivity," but not productivity itself. A soil can be fertile, but the yield on it can be low due to drought, poor agricultural practices, or an incorrectly chosen variety. Conversely, a high yield can be obtained on less fertile soil by applying intensive technologies. But this will be the result of high artificial fertility, not a natural property of the soil.

"Artificial fertility cannot exist separately: combining with natural fertility, it forms a qualitatively new category—natural-economic (natural-anthropogenic) fertility" (Mukha et al., 2003, p. 185).

Therefore, when discussing fertility, we are always talking about a property of the soil, about its internal organization and potential. Plants, on the other hand, are tools that allow us to assess the effectiveness of this potential, but they are not its source.

What Constitutes Fertility? Integration of Knowledge

Fertility is a systemic property that arises from the interaction of four groups of factors, corresponding to sections of previously studied modules. To understand fertility, we need to recall everything we know about soil. Simply put, fertility is a balanced combination of:

1. Physical Basis (Module "Soil Physics"):

• Particle size distribution (the ratio of sand, silt, and clay)—determines the water-air regime and absorption capacity.
• Structure—the ability of soil to form aggregates. It is structure that ensures the optimal ratio of solid, liquid, and gaseous phases. As E.V. Shein wrote (cited in Weil & Brady, 2017), structure is the "skeleton" of soil fertility.
• Density and porosity—determine the availability of oxygen for roots and microorganisms, as well as water permeability.

2. Water and Air Regimes (Modules "Water" and "Air"):

• Water—the main solvent and transport medium for nutrients. Fertility is impossible without sufficient, but not excessive, moisture (Scheffer et al., 2018).
• Air—plant roots and aerobic microorganisms need oxygen for respiration. Soil fertility is closely linked to its aeration.

3. Chemical Basis (Modules "Chemical Properties" and "Organic Matter"):

• Humus content—is the heart of fertility. Humus is not just "dead" organic matter but a complex complex that determines the absorption capacity, buffering capacity, nutrient reserve (primarily nitrogen), and water-physical properties (Baldock, 2012).
• Reaction of the environment (pH)—affects the availability of all nutrients. In too acidic or alkaline conditions, even a rich soil can be infertile for many crops (Weil & Brady, 2017).
• Reserves of available elements—macro- (N, P, K, Ca, Mg, S) and micronutrients (Fe, Zn, Cu, Mn, etc.).

4. Biological Activity (Module "Soil Biota"):

• Microorganisms—the main "processors" of organic matter. They mineralize humus, converting elements into forms available to plants. Without them, the cycle of substances in the soil would be impossible (Huang, 2012).
• Soil fauna (worms, insects, etc.)—create macropores, improve aeration, and mix soil layers.

All these components do not exist in isolation. They form a unified system. For example, poor structure (physics) worsens the water-air regime, which, in turn, reduces microbiological activity (biology) and slows down the release of nutrients from humus (chemistry). This is precisely why fertility is an integrative characteristic of the soil, not a sum of individual properties.

Fertility as a Dynamic Characteristic: Soil—a Renewable but Limited Resource

From our discussion follows a crucial conclusion: fertility is not a constant value. It is a dynamic property that can either increase (as a result of cultivation) or decrease (as a result of degradation).

"Soil fertility is characterized by high dynamism and clearly responds to changes in the factors and conditions of soil formation" (Mukha et al., 2003, p. 184).

Soil is, in a sense, a renewable resource. We can restore its fertility by applying fertilizers, adding organic matter, and using proper crop rotations. Nature is also capable of self-recovery, but this takes centuries.

However, despite its potential renewability, soil is a limited and extremely vulnerable resource:

• Recovery time. The formation of one centimeter of fertile topsoil can take from 100 to 400 years (Troeh & Thompson, 1993). The loss of this layer due to erosion can occur in a single season.
• Irreversibility of some losses. The disappearance of humus, destruction of structure, and loss of soil organisms are processes that are either irreversible or require enormous costs for restoration.
• Limited area. The area of soils suitable for agriculture on the planet is finite and is constantly shrinking due to urbanization, erosion, and degradation (Brady & Weil, 2017).

Understanding this paradox—the dynamism and simultaneous vulnerability of fertility—has led to the formation of the concept of sustainable soil management.

This concludes the first chapter of our lecture. We have examined how the understanding of fertility has changed, why it is a property of the soil and not of plants, and what components form it. This is the foundation upon which we will build further discussion. In the second chapter, we will move on to how this knowledge is applied in practice within the framework of sustainable soil management.

Distinguishing Concepts: A Fundamental Question for the Agronomist

In the previous chapter, we established that fertility is the ability of the soil to provide plants with everything they need. But a natural question arises: if plants grow on the soil and produce a yield, could fertility be a property of the plant itself—its ability to effectively use what the soil provides? Or perhaps fertility is the result of the joint work of soil and plant?

These questions are not idle. The answer determines our entire farming system: how we assess land, what technologies we apply, how we build crop rotations, and how we understand degradation. If we answer incorrectly, we will treat the wrong "disease" with the wrong "medicines."

Key thesis of this chapter: fertility is a property of the soil as a natural body. Plants are "users," not "creators" of this property (although they do influence it).

Fertility as an Attribute of the Soil Body

Let us recall V.V. Dokuchaev's fundamental discovery: soil is an independent natural body. Like any natural body, it possesses a set of its own, inherent properties. Fertility is one such property that distinguishes soil from rock (Scheffer et al., 2018).

Fertility is the main specific property of soil, qualitatively distinguishing it from the original (parent) rock (Mukha et al., 2003, p. 184).

This means that fertility is "built into" the soil; it is an integral characteristic, much like color, density, or porosity. It exists in the soil regardless of whether a plant is growing on it or not.

Take, for example, chernozem lying fallow. There are no cultivated plants on it, yet it remains fertile. Its fertility is a potential, a reserve accumulated over millennia of the sod process. And this potential can be realized as soon as plants appear. Conversely, desert sand remains infertile, even if rare plants temporarily appear on it. Fertility is an immanent property of the soil material itself, not a result of its use.

Potential and Effective Fertility: The Key to Understanding

To definitively distinguish between a soil property and the result of its use, soil science has introduced two key concepts, which we have already mentioned.

Potential fertility (also called natural or inherent)—is "a characteristic of the soil determined by its natural, genetic features and inherent to the soil as a natural body" (Valkov et al., 2004, p. 436). It is assessed by reserves of humus, nutrients, physicochemical properties, structure, etc. This is the soil's capital.

Effective fertility (or actual)—is "the degree of use of these possibilities" (ibid.). It is that part of the potential fertility that is realized in the yield under specific conditions of the year, technology, and variety. This is the income from the capital.

Imagine two chernozems with the same potential. On one, the farmer applies intensive technology, uses fertilizers, and irrigates—and gets a high yield. On the other, the farmer manages extensively, without fertilization—and the yield is low. The potential fertility of these soils is the same, but the effective fertility is different. The reason for the difference lies not in the soil but in how the farmer (and the plants) managed its potential.

Currently, fertility is understood as the ability of the soil, as a component of the biosphere, to provide the terrestrial factors and conditions necessary for plant life... Natural fertility characterizes the initial potential capabilities of the soil, while actual (effective) fertility characterizes the degree of use of these capabilities (Mukha et al., 2003, p. 185).

Thus, effective fertility is already a result of the interaction of soil, plant, climate, and humans. But its basis, its root, is the potential fertility of the soil itself.

Ecological Specificity of Fertility: A Soil Property, but Not Absolute

Another important argument for fertility being a property of the soil lies in its ecological specificity. The same soil can be fertile for some plants and completely infertile for others. This is a property of the soil, not the plant.

As Pliny the Elder wrote: "The soil that is adorned with tall and stately trees is by no means the best, except for its suitability for the trees themselves" (cited in Valkov et al., 2004, p. 439).

Valkov et al. (2004, p. 438) emphasize: "The main paradox of fertility is that all soils possess fertility, and yet there are no generally fertile lands at all. Their fertility is very specific." Tea and lupine grow only on acidic soils, while alfalfa prefers neutral ones. Heavy structural soils are optimal for grains, while potatoes do better on lighter ones. On soils rich in organic matter, the quality of grapes and tobacco decreases, while hemp and vegetables require precisely such soils.

This diversity of requirements is not a property of plants but a reflection of the diversity of soils. It is precisely because soils have different properties (pH, particle size distribution, humus content, etc.) that they differently match the ecological needs of different plants. Soil fertility is its correspondence to the needs of a specific plant. If we change the plant, we change the assessment of the fertility of the same soil. But the property remains a property of the soil.

Distinction from Agrochemistry and Crop Science

For us agronomists, this distinction has fundamental practical significance.

Agrochemistry studies the transformations and application of fertilizers. Fertilizers are a means of managing fertility, but they are not fertility itself. Fertilizers can increase effective fertility by compensating for the removal of elements, but they do not create fertility "from scratch." As stated in the law of return, we return to the soil what was taken from it. The soil remains the "master" of fertility, and fertilizers are just a tool. Without the soil matrix, its structure, and its buffering capacity, fertilizers would be just a saline solution, incapable of ensuring sustainable growth.

Crop science studies the technologies of cultivating crops. It uses soil fertility, creating optimal conditions for its realization (sowing dates, plant density, pest control). But fertility itself is not created in the field—it is delivered to the field by the soil's inherent property. An outstanding breeder can create a variety that better utilizes phosphorus from inaccessible compounds, but he will not create phosphorus in the soil. He will only "teach" the plant to better use what is there.

Why is This Important for Understanding Sustainability?

Recognizing that fertility is a property of the soil has profound implications for land resource management.

1. Fertility can be destroyed. If it is a property of the soil, then it can be lost—through erosion, dehumification, salinization, and compaction. The loss of fertility is a change in the soil itself, its internal organization.

2. Fertility can be restored, but slowly. Restoring fertility means restoring the properties of the soil, not just applying fertilizers. This takes time, organic matter, and structure formation.

3. Fertility is a common foundation for all crops. That is why the basis of agriculture is care for the soil, not just for the plants. Sustainable agriculture begins with the preservation and enhancement of soil fertility as a property of the soil itself.

To summarize: fertility is not the ability of a plant to absorb elements, nor the result of agronomic practices. It is a fundamental property of the soil, its internal capacity to meet the needs of plants. Plants, agrochemistry, and crop science only determine how fully this potential will be realized in a particular yield. Understanding this distinction is the basis for correctly diagnosing soil problems and developing strategies for their sustainable management.

Key takeaways from Chapter 2:

1. Fertility is an attribute of the soil as an independent natural body, existing independently of the presence of plants.

2. The distinction between potential (natural, inherent in the soil) and effective (realized in the yield) fertility clearly separates the soil property from the result of its use.

3. Fertility is ecologically specific: the same soil is fertile for some plants and infertile for others, determined by the properties of the soil itself (pH, texture, humus).

4. Agrochemistry and crop science are management tools for fertility, not its creators. They affect effective fertility without changing the potential (or changing it only in the long term).

5. Recognizing fertility as a property of the soil obliges us to responsible management of soil resources, since the loss of this property is the loss of the very basis of agricultural production.

Integration of Knowledge: Fertility as a Systemic Property

Now that we have established that fertility is a fundamental property of the soil itself, a natural question arises: what specific components does it consist of? Can fertility be measured by a single indicator, such as humus content or nitrogen reserves?

The answer is no. Fertility is a systemic, integrative property that arises from the interaction of many factors. It is similar to human health: it cannot be reduced to a single indicator like temperature or blood pressure. Health is the result of the coordinated work of all body systems in their interrelation.

Similarly, fertility is the result of the balanced work of all soil components. In this chapter, we need to show how the knowledge you gained in previous modules (soil physics, chemistry, biology) integrates into a unified understanding of fertility.

The level of potential soil fertility is determined by: humus content and its quality... nutrient content... particle size distribution... composition of exchangeable cations... microbiological and enzymatic activity (Mukha et al., 2003, p. 186).

Let's examine these components sequentially.

1. Physical Factors of Fertility

The physical properties of the soil create the environment in which all chemical and biological processes take place. They determine whether roots have space to grow, whether there is enough air for respiration, and whether water can infiltrate and be retained in the soil.

2. Water and Air Regimes

Water and air are the environment in which roots and microorganisms live. Their ratio and availability determine whether the fertility potential will be realized.

3. Chemical Factors of Fertility

The chemical properties of the soil are its "chemical kitchen," where some substances are transformed into others, and elements move from unavailable to available forms.

4. Biological Factors of Fertility

Soil is a living system. Billions of organisms in every gram of soil are not passive inhabitants but active participants in the processes that determine fertility.

Soil Solution—The "Node" of Interaction of All Factors

All these factors—physical, chemical, biological—converge in the soil solution. This is the environment from which plants directly receive nutrition. The soil solution is not just water; it is a complex solution of ions, organic acids, gases, and other substances.

• It is here that ions emerge from the surface of colloids into an available form.
• It is here that microorganisms secrete enzymes and organic acids.
• It is here that "buffering" occurs—regulating the concentration of ions when they are consumed by plants.

Plants absorb elements from the soil in ionic forms, and these ions are in the soil solution—the most available form (Eash et al., 2016, p. 8).

Unity and Interconnection of Factors

All the factors described—physical, water-air, chemical, and biological—do not exist in isolation. They form a unified system where a change in one component entails changes in all the others.

This can be represented as a diagram:

Structure → Water-air regime → Microbiological activity → Mineralization of organic matter → Supply of available elements to the soil solution → Plant nutrition → Supply of organic matter to the soil → Influence on structure (closing the cycle).

Or, as Valkov et al. (2004, p. 436) wrote: Soils have a special organomineral composition... they acquire a specific property—fertility—the ability to ensure plant growth and productivity. This property is born at the intersection of the mineral and organic, the living and non-living, in the endless cycle of substances.

Therefore, when assessing fertility and planning measures to increase (or restore) it, we must take into account all these factors in their interrelationship. It is impossible, for example, to improve the chemical composition of the soil while maintaining poor structure. It is impossible to add organic matter and ignore biological activity. Fertility is a holistic property of the soil system.

Link with Humus Content: A Key Integral Indicator

Of all soil properties, humus content (or organic carbon) is the most integral indicator of fertility. Why?

1. Humus is closely linked to soil physics. Its content determines the ability to aggregate, structure, and water-holding capacity.

2. Humus is the basis of chemical fertility. It determines CEC, buffering capacity, and reserves of nitrogen and other elements.

3. Humus is an indicator of biological activity. Its formation and transformation are the result of the work of soil biota.

Good humus content... near-neutral or neutral reaction of the soil solution, calcium saturation, high buffering capacity, granular-cloddy structure and favorable agrophysical properties, large reserves of nutrients—all this is the result of the chernozem (sod) soil-forming process (Mukha et al., 2003, p. 195).

Humus content is like an "integral portrait" of fertility. Therefore, any fertility management ultimately comes down to managing the content and quality of soil organic matter—through crop rotations, organic and mineral fertilizers, and tillage.

Summary: Fertility as a Result of Balanced Interaction

Let's summarize.

Fertility is not reducible to any one component. It is the result of a complex and balanced interaction of:

• Physical properties (structure, particle size distribution, density), ensuring the root environment.
• Water and air regimes, determining root respiration and water availability.
• Chemical properties, primarily humus content and cation exchange capacity, which create the nutrient potential.
• Biological activity, which carries out the conversion of unavailable substances into available ones and maintains the cycle of elements.

All these components converge in the soil solution—that very "life-giving moisture" directly consumed by plants.

This is precisely why fertility management is not about "feeding" plants (that is the task of agrochemistry) nor just "tilling" the soil (that is the task of agronomy). It is integrated management of the entire soil system aimed at preserving and enhancing its ability to provide plants with everything they need in the long term.

Key takeaways from Chapter 3:

1. Fertility is composed of physical, water-air, chemical, and biological factors that are closely interrelated.

2. Soil structure and humus are the two central elements around which all fertility is organized.

3. The soil solution is the "node" of interaction of all factors and the environment from which plants receive nutrition.

4. All components of fertility form a unified system, where a change in one factor entails changes in all others.

5. Humus content is an integral indicator reflecting the state of all components of fertility and is therefore key for monitoring and management.

Two Views of Soil: Capital or Consumable Material?

In previous chapters, we came to understand that fertility is a complex, integrative property of the soil, formed at the intersection of physical, chemical, and biological processes. A natural question arises: if fertility can be restored (by applying fertilizers, organic matter, improving structure), does that mean soil is an inexhaustible resource?

The answer is both "yes" and "no." Soil is capable of self-recovery; it is renewable—but only under certain conditions and within certain time scales. However, this renewability has strict limits, and ignoring them leads to irreversible degradation.

Due to its ability to self-repair, soil can, to some extent, resist degradation. But these limits are very narrow, and the rate of natural recovery is extremely slow compared to the rate of anthropogenic destruction (Troeh & Thompson, 1993, p. 8).

Therefore, we must view soil simultaneously as both a renewable and a limited resource. This apparent contradiction is the key to understanding the modern problem of sustainable land use.

Why is Soil a Renewable Resource?

The renewability of soil is ensured by two main processes.

Why is Soil a Limited Resource?

The limitation of soil as a resource manifests in several aspects: temporal, spatial, and functional.

Soil in the Context of Sustainable Development

The modern understanding of soil as a limited resource has led to the formation of the concept of sustainable soil management. This concept underlies many international documents, including:

• FAO World Soil Charter (1982, revised in 2015).
• European Soil Protection Strategy (2006).
• National legislation.

The main principles of sustainable soil management are:

1. Irreplaceability. Soil fertility cannot be replaced by any technology (hydroponics—only for limited crops).

2. Resource limitation. Soil is a finite resource, and its use must be rational.

3. Necessity of reproduction. To preserve fertility, it is necessary to return to the soil what is taken from it (the law of return).

4. Prevention of degradation. It is easier to prevent the loss of fertility than to restore it.

5. Accounting for time. The rate of soil recovery is incomparably slower than the rate of its destruction, so the rate of degradation must be minimized.

The Paradox of Soil Fertility in the Anthropocene

The modern geological epoch, called the Anthropocene, is characterized by the dominant influence of humans on all natural processes, including soil formation (Richter & Tugel, 2012).

Humanity has become the main factor in soil formation and can cause changes in soils through individual events or long-lasting phenomena (Richter & Tugel, 2012, p. 38-2).

Today we face a paradox:

• On the one hand, our knowledge and technology allow us to sharply increase soil fertility (breeding, fertilizers, reclamation, irrigation, precision farming).
• On the other hand, anthropogenic pressure on soils (intensification, urbanization, pollution) leads to their accelerated degradation, reduced fertility, and even complete loss.

The result of human economic activity can be both improvement of the original virgin soils and their deterioration, a decrease in potential and effective fertility (Mukha et al., 2003, p. 185).

We can, using modern technology, obtain high yields on soils with low natural fertility. But the price of this is often an additional burden on the soil, which leads to its degradation. Conversely, the irrational use of even the most fertile chernozems leads to their depletion.

This is the central contradiction of modern agriculture: we can temporarily increase yields, but in the long term, we risk losing the very basis of fertility.

This is precisely why the transition to sustainable soil management is not just a "good idea" but an urgent necessity for the survival of human civilization.

Summary: Soil—Capital We Must Not Consume but Multiply

Let's summarize.

Soil is simultaneously a renewable and a limited resource:

• Renewability is ensured by natural soil formation and the possibility of anthropogenic restoration (fertilizers, organic matter, reclamation).
• Limitation is determined by:
• the extremely slow rate of natural formation (100–400 years per 1 cm of topsoil);
• the finite area of suitable land;
• the irreversibility of many degradation processes (erosion, dehumification, salinization, contamination, compaction);
• the exhaustibility of individual components (e.g., phosphorus).

On the scale of a human lifetime, soil is a practically non-renewable resource. Therefore, the main task of modern agriculture is not just to obtain a harvest but to preserve and enhance soil fertility for future generations.

This is the essence of sustainable soil management—the topic of the next chapter.

Key takeaways from Chapter 4:

1. Soil is renewable thanks to natural soil formation and anthropogenic restoration.

2. However, this renewability is extremely limited in time (hundreds of years for recovery) and in area (suitable land is finite).

3. Many types of degradation (erosion, dehumification, salinization, contamination, compaction) are practically irreversible in the foreseeable future.

4. In the Anthropocene era, humans have become the main factor in soil formation but often accelerate degradation rather than restoration.

5. Therefore, soil should be considered a non-renewable resource on the scale of a human lifetime, requiring especially careful treatment.

6. Sustainable soil management is not a choice but a necessity, driven by the finiteness and vulnerability of the soil resource.

From Exploitation to Sustainability: Why a Paradigm Shift is Necessary

Throughout most of the history of agriculture, humans treated soil as an inexhaustible resource. The farmer took as much from the land as he could, and when yields fell, he simply moved to a new plot, leaving the depleted lands for "self-recovery" (Troeh & Thompson, 1993; White, 2006). Such a strategy was possible while population density was low and free land was available. Today, the situation has changed radically.

In the 20th century, the intensification of agriculture, the "Green Revolution," and the widespread use of fertilizers and pesticides made it possible to dramatically increase food production. However, the price of this success was high:

• Accelerated soil erosion (Weil & Brady, 2017, Ch. 17; Valkov et al., 2004, pp. 465–466).
• Decrease in organic matter content (dehumification) (Mukha et al., 2003, p. 477).
• Salinization and alkalinization of irrigated lands (Eash et al., 2016, Ch. 9; Valkov et al., 2004, pp. 472–474).
• Contamination with heavy metals and pesticides (Valkov et al., 2004, pp. 476–483).
• Compaction and destruction of structure (White, 2006, pp. 245–246).
• Loss of soil biological diversity (Weil & Brady, 2017, Ch. 20).

As a result of economic activity, soil often loses its fertility, degrades, or is even completely destroyed. This happens when human activity is irrational and environmentally unsound (Valkov et al., 2004, p. 461).

It became clear that the traditional strategy of "maximizing yields at any cost" leads to depletion and degradation of the soil resource. A new paradigm emerged—sustainable soil management.

Definition of Sustainable Soil Management

In its most general form, sustainable soil management (SSM) is a system of measures aimed at preserving and enhancing soil fertility, preventing its degradation, and ensuring long-term productivity with minimal negative impact on the environment.

A more formal definition is given in FAO documents (FAO, 2015): sustainable soil management is the use of soil resources in such a way as to maintain or increase their productivity, preserve or improve environmental quality, and contribute to human well-being, without undermining the soil's ability to perform its ecosystem functions for future generations.

In the Russian tradition, this concept is closely linked to soil protection and rational land use.

Soil protection and rational use is a system of measures aimed at protecting, improving, and rationally using lands, increasing soil fertility, and maintaining the sustainability of the biosphere as a whole (Valkov et al., 2004, p. 461).

Thus, sustainable soil management is not just a set of agronomic practices but a systemic strategy based on a deep understanding of soil processes and ecological laws.

Principles of Sustainable Soil Management

Unlike specific agrotechnologies (tillage, crop rotations, fertilizers), which are studied in other courses, sustainable management is based on fundamental principles. Let's examine them in more detail.

The Concepts of "Soil Health" and "Soil Quality"

In modern science and practice, the terms "soil health" and "soil quality" are increasingly used. These concepts are closely related to sustainable management but have different emphases.

Sustainable Management as a Systems Approach

In summary, sustainable soil management is not a set of recipes but a systems approach that:

1. Recognizes soil as a living system, not just a substrate.

2. Considers all soil functions (productive, regulatory, biotopic, informational), not just yield.

3. Strives for balance between the use and reproduction of fertility.

4. Focuses on the long-term perspective, not on short-term gain.

5. Adapts to local conditions and continuously learns based on monitoring.

Mitigating the contradictions between natural and anthropogenic systems is possible only within the framework of stable socio-economic development that does not destroy its natural basis (Mukha et al., 2003, p. 475).

Sustainable soil management is not "another agronomic practice" but a philosophy of land use that should permeate all agronomist's decisions: from crop selection and tillage to fertilization and plant protection systems.

Summary

Sustainable soil management is a system of measures aimed at preserving and improving all soil functions while minimizing negative environmental impact, ensuring long-term productivity and environmental sustainability.

Key principles:

1. Conservation of all soil functions.

2. Prevention of degradation.

3. Maintaining and increasing organic carbon stocks.

4. Preserving structure and preventing compaction.

5. Maintaining biological activity and diversity.

6. Adaptation to local conditions.

The concepts of "soil quality" and "soil health" serve as the basis for assessment and monitoring, with the former being more functional and the latter more integrative and ecosystem-oriented.

Ultimately, sustainable management is not just an agronomic task but a global strategy for human survival under conditions of limited soil resources and growing needs.

Key takeaways from Chapter 5:

1. The traditional exploitative model of agriculture is unsustainable in the long run.

2. Sustainable soil management is a systemic strategy, not a separate agronomic practice.

3. Its principles cover all functions of the soil, not just the productive one.

4. Prevention of degradation is the most important principle, as restoration takes centuries.

5. Organic matter and structure are central objects of management.

6. "Quality" and "health" of soil are interrelated but different concepts: quality is a functional assessment, health is integrative and ecosystem-oriented.

7. Sustainable management adapts to local conditions and requires constant monitoring.

From Property to State: Evolution of the View on Soil

In classical soil science, fertility was traditionally viewed as the soil's ability to supply plants with nutrients, water, and physical support. This was a utilitarian, productive characteristic. However, as knowledge accumulated about the complexity of soil processes and the role of soil in global ecosystems, it became clear that fertility is just one facet of a much broader concept—soil health.

Soil health implies self-regulation, stability, resilience, and the absence of stress symptoms in the soil as an ecosystem. Soil health describes the biological integrity of the soil community—the balance among organisms in the soil, as well as between soil organisms and their physical and chemical environment. (Weil & Brady, 2017, p. 1001).

Soil health is the integrative state of the entire soil system, which includes not only the ability to produce a yield (fertility) but also the ability to self-regulate, resist stresses, maintain biological diversity, and perform all ecosystem functions. Fertility, therefore, is a necessary but not sufficient condition of soil health.

This distinction has profound practical meaning. A soil can be fertile today—producing high yields thanks to intensive application of fertilizers and pesticides. But its health may be undermined: structure destroyed, biological activity suppressed, resistance to drought or diseases reduced. Such a soil is "sick," even if it is temporarily productive.

A fertile soil provides a steady supply of dissolved mineral nutrients... but a healthy soil is not just fertile: it is resilient, self-regulating, and capable of maintaining its functions in the long term. (Weil & Brady, 2017, p. 22).

Thus, the task of the modern agronomist is not just to maintain fertility but to restore and maintain soil health, which will automatically ensure sustainable fertility.

What is Soil Health and What Does It Consist Of?

Soil health is a state in which the soil as a living system is capable of performing all its ecological functions in full and at the same time maintaining resilience to external influences. It consists of three interrelated components:

Indicators of Soil Health

To assess soil health, sets of indicators have been developed to diagnose the state and track changes (Weil & Brady, 2017, Ch. 20). These indicators are divided into three groups, corresponding to the three aspects of health.

Soil Health and Resilience

One of the key aspects of soil health is its resilience—the ability to recover after disturbances (drought, waterlogging, mechanical loads, pollution). Resilience is contrasted with resistance (the ability not to change under influence), but both characteristics are important for sustainable management.

Soil resistance is the ability to maintain functional integrity under the influence of external factors, and resilience is the ability to restore functional and structural integrity lost after the impact of external factors or prolonged stress. (Richter & Tugel, 2012, p. 38-8).

A healthy soil possesses:

• High resistance—it does not lose its functions under normal agronomic loads.
• High resilience—it recovers quickly after stress events (e.g., after drought or the passage of heavy machinery).

Resilience is ensured by:

• Biological diversity—the presence of many species duplicating functions allows the system to "survive" the loss of one component.
• High organic matter content—it improves structure, increases buffering capacity, and water-holding capacity.
• Developed root system of plants—roots create macropores and support aggregation, and also serve as a source of organic matter.
• Balanced microbial communities—they quickly respond to changes and restore their functions.

Resilience is a crucial component of soil health. A soil with high resilience quickly recovers from disturbances, while a soil with low resilience may remain degraded for a long time. (Weil & Brady, 2017, pp. 1010–1011).

Loss of resilience is one of the first signs of deteriorating soil health, which can remain unnoticed against the background of temporarily high yields.

Fertility as Part of Soil Health

What is the place of fertility in the concept of soil health? It can be said that fertility is an integral, but not the only, component of health. Soil health includes fertility but goes beyond it, encompassing:

• Ability for self-regulation—maintaining balance between processes of accumulation and mineralization of organic matter, between absorption and release of elements.
• Ability for purification—neutralization and decomposition of pollutants.
• Ability to support biodiversity—creating conditions for the existence of many species.
• Ability for long-term functioning—preserving all ecosystem functions over decades and centuries.

In other words, fertility is the "productive" component of health, but a healthy soil must also be "clean," "living," and "stable."

Interestingly, in scientific literature, the concepts of "soil quality" and "soil health" are often used interchangeably, but many authors emphasize the distinction:

The term "soil health" is best applied to soil as an ecosystem, emphasizing its biological integrity and self-regulation, while "soil quality" has a more utilitarian character, focusing on the suitability of the soil for performing specific functions. (Weil & Brady, 2017, pp. 1001–1002).

In the Russian tradition, this distinction is also reflected: "fertility" is a narrower, agronomic concept, while "ecological state" or "health" is broader, including all ecosystem functions (Valkov et al., 2004; Mukha et al., 2003).

Practical Significance: Managing Soil Health

The transition from managing fertility to managing soil health has important practical implications:

Conclusion: Soil Health as the Foundation of Sustainable Agriculture

In this chapter, we have shown that fertility is an important but only one component of the broader concept of soil health. Healthy soil is not only fertile but also biologically active, structurally stable, self-regulating, capable of resisting stresses, and recovering from disturbances.

The transition from managing fertility to managing soil health requires:

• Understanding soil as a living ecosystem, not just a substrate.
• Using comprehensive indicators (physical, chemical, biological).
• Applying preventive, adaptive management strategies.
• Integrating all agronomic practices into a unified system.
• Continuous monitoring and adjustment.

Ultimately, it is soil health that ensures long-term and sustainable fertility—what is necessary for food security and environmental preservation in the Anthropocene.

Key takeaways from Chapter 6:

1. Fertility is the soil's ability to provide plants with life factors, while soil health is the integrative state of the entire soil ecosystem, including self-regulation, resilience, and the performance of all ecological functions.

2. Soil health consists of physical, chemical, and biological health, closely interrelated.

3. Soil health indicators include biological (microbial biomass, respiration, enzymes), physical (aggregate stability, density), and chemical (humus, pH, available elements) parameters.

4. Resilience—the ability to recover from stress—is a key characteristic of healthy soil.

5. Managing soil health is a preventive, integrative, and adaptive strategy that goes beyond traditional fertility management.

6. Ultimately, soil health is the foundation of sustainable fertility, capable of being maintained in the long term.