Soil functions

The type and distribution of flora in a landscape are influenced by several factors, including soils, climate, and relief or topography. Although many plants can tolerate a wide range of conditions, virtually all species have a set of ideal conditions for their growth and survival. Beyond this set of ideal conditions, plants will struggle more to survive and compete against other plants that are better suited to those differing prevailing conditions. The main soil factors that influence the flora in any place are acidity or alkalinity and the degree of wetness. The combination of soil, climate, and topography worldwide gives rise to a diverse range of flora across the globe, including trees. Soil plays an important role in supporting ecosystem services, such as 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. Understanding the factors that influence the distribution of plants and animals is crucial for conservation efforts and predicting the impacts of environmental changes on biodiversity.

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

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.

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

The soil is a complex system that plays a vital role in supporting life on Earth. A healthy soil has a natural balance between micro-organisms, animals, nutrient and water cycles, physical structure, and chemical makeup. However, soil and land can become damaged environmentally by various means, such as previous industrial, mining, and land-fill activities, and poor agricultural practices. Once damaged, the soil system cannot work properly, and the delicate balance between all the parts that make up the healthy soil becomes disrupted. This can lead to the impossibility of animal life in the soil and the cessation of the complex web of interactions in the soil. Soil restoration is the process of restoring the functions of soil back into working order, similar to coaxing a damaged motor engine back into life.

Habitat restoration is now an important part of nature conservation, and government planning regulations encourage restoration by making money available to fund restoration of existing damaged sites. It is essential to understand the way that the soil system works when undertaking such projects, so that their plans can have the most significant positive effect. Understanding the soil and ecological conditions in nearby surrounding landscapes can help guide the correct course of action, such as choosing which plant types to encourage to enhance biodiversity and developing links between habitats in the landscape, allowing animals to travel between locations.

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. For any habitat restoration project to be successful, it is crucial to understand the existing soil conditions and the kinds of vegetation and habitats these can sustain. Restoration projects should use the existing properties and distribution of soils to guide opportunities for habitat restoration. These properties are the result of centuries, if not millennia, of change caused by forest removal, grazing, cultivation, climate change, and environmental pollution. Understanding the dynamics of soil-water interactions is crucial for various applications, including agriculture, water resource management, and environmental conservation.

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.

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 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. Soil Type: Different soil types, such as clay, loam, or sandy soils, have varying characteristics that affect water drainage, nutrient retention, and root development.

2. Acidity or Alkalinity: The pH level of the soil determines its acidity or alkalinity. Some plants prefer acidic soils, while others thrive in alkaline conditions. Adjusting the pH level can be done through the addition of soil amendments.

3. Moisture Content: The moisture level of the soil is important for plant growth. Some plants require well-drained soils, while others prefer moist or even waterlogged conditions. Proper irrigation practices can help maintain the ideal moisture content.

4. Texture and Workability: Soil texture refers to the relative proportions of sand, silt, and clay particles. The texture affects the soil's ability to retain water and nutrients, as well as its workability for planting and cultivation.

5. Organic Matter: The presence of organic matter, such as compost or well-rotted manure, improves soil structure, water-holding capacity, and nutrient availability. Adding organic matter can enhance the fertility and health of the soil.

6. Depth and Structure: The depth of the soil determines the root zone available for plants to establish themselves. Soil structure, which refers to the arrangement of soil particles and pore spaces, affects water infiltration, aeration, and root penetration.

Understanding these soil characteristics allows gardeners to make informed decisions about soil amendments, irrigation practices, and plant selection. By optimizing the soil conditions, gardeners can create an environment that supports healthy plant growth and maximizes the potential of their gardens.

Sources:

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