Soil provides many important functions for plants, animals, and humans. Here are some of the key functions of soil:
These functions of soil are important for various agricultural, environmental, nature protection, landscape architecture, and urban applications. Soil is our life support system, and without it, human life would be very difficult.
Trees have been supported by soils for around 350 million years, and the relationship between trees and soil is extremely important. Trees rely on the soil for anchorage, nutrients, and water. Trees grow in height by division of cells at the tips of their branches, while the girth or diameter of the tree grows by cell division in the layer between the bark and the main woody part of the trunk. Most of the nutrients required by trees are taken up from the soil and passed dissolved in water to the growing tree via the roots. The soil is the storage place for water and the nitrogen and minerals dissolved in water, which are needed by the tree to live and grow. Without soil, there would be few, if any, trees. Trees play a significant role in reducing erosion and moderating the climate. They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Trees and forests provide a habitat for many species of animals and plants. Trees provide shade and shelter, timber for construction, fuel for cooking and heating, and fruit for food as well as having many other uses. Tree roots hold soil in place, reducing erosion, and trees lessen the force of storms and reduce the amount of runoff into sewers, streams, and rivers, improving water quality. One hundred mature trees can intercept about 100,000 gallons of rainfall per year. Trees are sometimes called the lungs of the Earth because they absorb pollutants through their leaves, trapping (or “sequestering”), and filtering contaminants in the air. One tree can sequester (or take in) more than one ton of carbon dioxide in its lifetime. Planting trees and avoiding deforestation are key measures in mitigating climate change
Soils and water
Much of the precipitation in the form of rain and snow falls on the surface of the soil. The nature of the soil plays a crucial role in determining what happens to this precipitation. Depending on the type of soil, some of the precipitation will flow over the surface, some will enter the soil and be held for a period of time, and some will pass through the soil to groundwater, rivers, lakes, and eventually the oceans. The period that water remains in the soil is vital for agriculture, food production, plant life, and soil organisms.
Soil water regime, which is dependent on the water-holding capacity of the soil, the demands of plants and animals, and the availability of soil water, influences the fate of water entering the soil. The texture of the soil, such as clayey, loamy, or sandy, and the structure of the soil, which refers to the network of pore space, determine how strongly water is held in the soil.
After heavy rainfall, the soil is usually saturated, and the water is held at field capacity, which is the maximum amount of water that a particular soil can hold for plants. As the rainfall stops, the surplus water drains through the soil, causing the soil to gradually dry out. If there is no further rainfall for an extended period, the soil may reach the permanent wilting point, where plants begin to wilt due to lack of moisture. This situation is common in low rainfall and drought-prone areas. The amount of water held in the soil and its tenacity are important factors that influence soil behavior and its usability.
Soil and water are interconnected, and this relationship is essential for supporting ecosystem services. Soil plays a vital role in supporting the life of plants and animals, filtering pollutants from water, and contributing to natural cycles such as the hydrological, nutrient, nitrogen, carbon, and oxygen cycles. The availability and retention of water in the soil are critical for sustaining plant growth and the overall health of ecosystems.
Understanding the dynamics of soil-water interactions is crucial for various applications, including agriculture, water resource management, and environmental conservation.
Farming and food production
Soils have been used for agriculture since the beginning of human civilization. Initially, farming was done with simple hand tools and crop yields were low. However, in the last century, there have been significant changes in agriculture. In highly developed parts of the world, such as the USA and Western Europe, farming is now highly mechanized, and improved methods of cultivating the soil, mechanization, and use of fertilizers have led to high levels of crop production. In contrast, other parts of the world, including areas with poverty and unsuitable climates, have made little progress in agriculture, and yields are still very low and unreliable from year to year.
Several factors determine whether and how a particular soil is suitable for agricultural production. The prevailing climate is important because crops need air, light, and rainfall. The general topography is also important, as it is difficult to manage and grow crops on steeply sloping land, and soils on steep slopes are prone to erosion. The soils themselves should be permeable, have good water-holding capacity, a good structure, and be well supplied with nutrients. Initially, agriculture developed on the best-suited land, but gradually farming has extended onto less suited land where conditions may include low rainfall, low nutrient content, and sloping land.
In the case of natural vegetation such as wildflowers and woodlands, many of the nutrients are recycled, with dead plant remains being passed directly back into the soil in-situ where they are broken down and made available again to other growing plants. This is not the case with crops; here, most of the plant is removed from the field when it is harvested. Relatively few crop remains fall to the ground, decompose, and return nutrients to the soil. Without some man-made additions, such as fertilizers, to replenish the nutrients, crops would not grow well. Some farming techniques try to release as many nutrients in the soil as possible. In previous years, it was common to see burning stubble in fields, with the ash releasing nutrients to the soil. Other techniques, such as 'direct drilling' and carefully managed rotations, seek to retain the soil's health and vitality
Soils and infrastructure
Humans have been building houses, roads, railways, canals, factories, and other buildings for centuries, which is known as infrastructure. Soil provides the support for the physical foundations of these constructions. Soil Mechanics is a well-developed science that seeks to understand the behaviour and suitability of soils for construction purposes. Soil Mechanics is a form of Civil Engineering that studies the physical properties and utilization of soils, especially used in planning foundations for structures and subgrades for highways. Soil Mechanics seeks to understand the behaviour and suitability of soils for use for construction purposes. Soil varies in texture, properties, and behaviour from place to place, and it is essential to have a good understanding of the soils on and in which buildings and other constructions are to be built. Failure to have this understanding can lead to catastrophic events with loss of life. Soil sealing is the process of covering over and building on soil, which usually completely prevents its use for other purposes in the future. Soil sealing is usually permanent, and once land is built on, it is rarely turned back to open countryside. Soil sealing has implications for the balance of land use into the future, as the more land used for building upon, the less will be available for food production and for supporting natural habitats.
As the world population continues to increase, so will the demand for housing and other parts of the infrastructure. It is important to understand the existing soil conditions and the kinds of vegetation and habitats these can sustain when undertaking habitat restoration projects. Restoration projects should use the existing properties and distribution of soils to guide opportunities for habitat restoration. Soil conditions, together with climate and the influence of other living things, such as animals and humans, can both limit and support plant growth and the development of plant communities. Understanding the dynamics of soil-water interactions is crucial for various applications, including agriculture, water resource management, and environmental conservation.
Soils and Archaeology
Soils have been a vital part of the earth for millions of years and have supported the developments of mankind for several thousand years. Soils often bear the imprint of occupation of the land by humans, plants, and animals, and the nature of the soil and its constituents have been used to help understand the complex history of earlier life on earth. The discovery of artefacts, treasure, and evidence of past human occupation in the landscape is fairly common, and the properties of soil play a crucial role in preserving these remains. Soil varies in its ability to preserve artefacts, treasure, and evidence of human occupation, and the decomposition of organic remains, such as bodies, in wet, poorly drained soils tends to be much slower than in dry soils. Soil Mechanics is a well-developed science that seeks to understand the behaviour and suitability of soils for construction purposes. Soil Mechanics is a form of Civil Engineering that studies the physical properties and utilization of soils, especially used in planning foundations for structures and subgrades for highways. Soil sealing is the process of covering over and building on soil, which usually completely prevents its use for other purposes in the future. Soil sealing has implications for the balance of land use into the future, as the more land used for building upon, the less will be available for food production and for supporting natural habitats. Understanding the dynamics of soil-water interactions is crucial for various applications, including agriculture, water resource management, and environmental conservation
Soils and climate change
World climates have undergone many changes over the past hundreds of million years, resulting in dramatic changes to landscapes, vegetation, animal life, and soil. These changes were caused by variations in the Earth's orbit in space. The last major climate change was an Ice Age about 2 million years ago. Over the last 20 years, following the warmest temperatures since recording began, major concerns have emerged that our climate is changing once again, but this time largely due to human activity, particularly to the burning of fossil fuels such as coal and oil. Scientists believe we are now entering a period during which climate change will occur faster than at any previous time, and these changes will have huge impacts on soils.
The Earth's surface is warmed by short-wave solar radiation from the sun, which drives most processes in the biosphere. As the radiation passes through the atmosphere towards the earth, some is reflected, some is scattered, and some is absorbed, but a proportion reaches the Earth's surface. Here, radiation is either absorbed or reflected. The solar radiation causes the Earth to warm up and give off its own thermal long-wave radiation. Gases such as carbon dioxide (CO2), ozone (O3), and water vapour in the atmosphere absorb some of this long-wave radiation reflecting it back to the Earth; the rest escaping into outer space. This reflection of thermal energy is called the Greenhouse Effect. The greenhouse effect of this warming caused by the interception of the long wave radiation by the natural so-called greenhouse gases is causing great concern among scientists. Human activity is undoubtedly bringing about the release of increasing amounts of gases into the atmosphere which increase this radiation back to the earth. These gases include carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons (CFLs), many of which are associated with industrial installations built in the last 150 years. Importantly, burning fossil fuels, such as coal and oil, releases carbon dioxide and other gases linked to the increase in greenhouse gases into the atmosphere. There is now scientific evidence that after being fairly constant for 1,000 years, atmospheric concentrations of carbon dioxide have gone up by 33% in the last 150 years.
Soils and health
Soils can affect our health in both good and bad ways. Some soils contain large amounts of particular elements that can cause medical and physical problems if taken in by humans and animals. Some soils don't have enough elements that are essential to human and animal health, which can also lead to problems. These elements come into our bodies in three main ways: through the food we eat, by breathing in soil as fine dust, and through cuts and scratches. Natural problems in the soil are relatively rare, but much more common are problems where human activity has led to polluted or contaminated soils. Human pollution of soils can be linked to industries such as mining for metals. Much pollution and contamination occurred during the development of industry from the 1800s onwards, although there are still soils today contaminated from Roman times. Soil contaminants can enter the food chain and cause disease and mortality in soil-dwelling, terrestrial, and aquatic organisms. The loss of biodiversity and biomass leads to a decrease in organic matter and changes in nutrient inputs and cycling, affecting the primary productivity of natural and agricultural ecosystems and leading to the overall loss of soil ecosystem services. The Environment Agency is responsible for encouraging and enforcing greater awareness of these problems and the clean-up of polluted contaminated land.
Planning and Land Quality
Land capability classification and land suitability classification are two main approaches to assessing land quality. These classifications help determine the suitability of land for different purposes, such as agriculture, building, or other specific uses.
Land capability classification focuses on the overall suitability of soils for most kinds of field crops. It provides a general assessment of the capability of soils to support agricultural production. This classification system is widely used and has been developed by organizations like the United States Department of Agriculture (USDA).
On the other hand, land suitability classification is more specific and focuses on assessing the suitability of land for defined uses, such as specific crops or pasture plants. It involves an in-depth assessment of the land's suitability for those particular purposes.
Both land capability and land suitability classifications play important roles in land management and decision-making processes. They help guide land use planning, agricultural practices, and environmental management. By understanding the suitability of the land, stakeholders can make informed decisions about how to best utilize and manage the land resources available to them.
It is crucial to consider these classifications in the context of increasing population and the need to provide food and other resources sustainably. Responsible land use is essential to ensure the long-term productivity and health of the land, as well as to minimize negative impacts on the environment.
Soils and Gardening
Soils play a crucial role in gardening and agriculture, as they provide the foundation for plant growth and nutrient uptake. Gardeners often inherit the soils in their gardens when they purchase a property, and it is not uncommon for these soils to require some adjustments to meet the specific needs of the desired plants. Here are some key aspects of soil that gardeners consider:
1 Penn State Extension: Managing Soil Health: Concepts and Practices2 ScienceDirect: Soil Health - an overview3 Nature: The Influence of Soils on Human Health4 FAO: Ecosystems impairment caused by soil pollution5 Steemit: Factors influencing vegetation6 Wiley Online Library: An Introduction to Soil Concepts and the Role of Soils in Watershed Management