Soils and Water Quality Soil Facts
Provides important ecosystem services that support different processes in nature, including nutrient cycling and gas exchange. In these cycles, water fluxes are important in cycling nutrients through the soil-plant-atmosphere pathway and are important in transferring nutrients and other particles from the soil to nearby water bodies. Soil can absorb rainwater, store it temporarily, and release it to plants and soil organisms. Soil also filters water-dissolved materials and releases water into surface water and groundwater.
In this article Pritish Halder describes the full theory of Soil and Water Conservation.
Erosion, Sedimentation, and Runoff
When soil is well managed, it can be an efficient rainwater sponge. If the soil is improperly managed, however, infiltration into the soil can be greatly reduced and the water may run off the surface, carrying soil particles with it. This process, called soil erosion, has been a major cause of soil degradation in North Carolina for many years (Figure 1). Further, damage to water quality occurs when this eroded soil enters surface waters.
Sedimentation occurs when water carrying eroded soil particles slows long enough to allow soil particles to settle out. The smaller the particle, the longer it stays in suspension. Larger, heavier particles such as gravel and sand settle out sooner than smaller, lighter particles such as clay. Clay may stay in suspension for very long periods, contributing significantly to water turbidity (cloudiness).
Comes from many sources, including agricultural fields, forestry operations, eroding streambanks, construction sites, and mining operations. Sediment is the largest water pollutant by volume in North Carolina. It affects water quality physically, chemically, and biologically. Damage from sediment is expensive, both economically and environmentally. Sedimentation destroys fish spawning beds, reduces useful storage volume in reservoirs, clogs streams, and makes costly filtration necessary for municipal water supplies.
Suspended sediment can kill aquatic plant life and alter a stream’s ecology. Because the environmental damage from sediment is often cumulative, the ultimate effects and costs may not be evident for years. The consequences of off-site sedimentation can be severe, both for people immediately affected and those who must cope with subsequent problems. Sediments are often organic matter, animal or industrial wastes, nutrients, and chemicals.
The most troublesome nutrient element is phosphorus. In freshwater ecosystems with typically very low phosphorus conditions, large additions of phosphorus can stimulate the production of algae blooms. As the algae die, microorganisms in the aquatic system decompose the algae, using it as a food source.
In the process, microbes also use significant amounts of oxygen. If the oxygen level is initially low, the decomposition process can further reduce it enough that fish kills can occur. Phosphorus may come from such sources as fertilizers, organic matter, and animal manure. Phosphorus is immobile in most soils and concentrates in the top few inches of the soil profile, which is susceptible to erosion. Therefore, phosphorus is likely to be present in runoff sediment.
The varying chemical properties of pesticides—for example, their solubility, toxicity, and chemical breakdown rate—determine the potential damage to water quality. Sediment also may carry pesticides, such as herbicides and insecticides, that may be toxic to aquatic plants and animals.
Certain dissolved nutrients and pesticides are highly mobile and can reach the groundwater by moving down through the soil (leaching). Nitrogen, in the form of nitrate (NO3-), is highly mobile and may cause human and animal health problems when concentrations exceed 10 milligrams of nitrogen per liter (44 mg of NO3-). In waters where nitrogen deficiency limits growth within the ecosystem, added nitrogen stimulates algae growth in the same manner as phosphorus. Despite the problems related to nitrogen leaching, some other nutrients present in fertilizers are not likely to cause environmental problems.
For example, chlorine, in the form of ion chloride (Cl-), is present in some fertilizers and is easily leached from the soil, though without any adverse effect on the environment. Likewise, ion sulfate (SO42-) and potassium (K+) also are present in some fertilizers; part of these nutrients can be leached depending on soil texture and rainfall, but they do not cause adverse impacts on the environment.
Household Wastewater Disposal
Soils can be used to filter and absorb the waste constituents of wastewater from septic systems. About half of North Carolina residents depend on septic systems (and hence on soil absorption) for the treatment and disposal of their household wastewater. More than 1 million housing units in the state use on-site septic systems to dispose of their wastewater. At least 30,000 additional septic tank systems are installed each year. Each day, septic systems in North Carolina discharge more than 100 million gallons of sewage into the soil.
Each region of North Carolina has its potential hindrances for septic tank installation. In the piedmont, installation is difficult in thin, shallow soils over bedrock and in clayey soils whose mineral content causes them to swell extensively when wet. In the coastal plain, problems with water contamination may result from a seasonally high water table that is close to the soil surface. In the mountains, installation is difficult on steep slopes, in shallow soils, and at the base of long slopes where subsurface water can accumulate. Alternatives to conventional septic systems need to be considered in these problem areas.
Land Application of Nutrient Containing Organic Materials
Municipalities and industries often apply sludge from wastewater treatment plants to agricultural land (see NC State Extension publication AG-439-3, Land Application of Municipal Sludge: Advantages and Concerns). Applications of livestock and poultry manure are popular because of an increase in their availability and new regulations governing manure management. Land application is an appropriate use of these products, provided their nutrient characteristics are known and matched with a suitable cropping system that will utilize these nutrients.
The characteristics of the wastes determine the allowable land application rates. Each waste type will contain one constituent that limits the amount that can be safely applied to land. This limiting constituent may be one of the plant nutrients such as nitrogen or phosphorus, one of the heavy metals such as zinc, copper, cadmium, or lead, or other constituents such as sodium or calcium carbonate. Waste regulations are administered by the state and recommendations are developed by North.
The development of a land treatment system must be tailored to the characteristics of the specific site and the specific waste. The following are among the characteristics that may disqualify a site: steep slopes; very clayey or sandy soils; nearby streams, wells, and property lines; a likelihood of flooding; and shallow depth to bedrock or the water table. Because each site has a finite capacity to accept certain waste constituents (for example, heavy metals such as zinc, copper, and cadmium), a threshold may be reached beyond which land application of wastes is no longer acceptable.
Soils in all climates, including Arctic ecosystems, are essential to the global carbon cycle. The BBC reports that the thawing of permafrost — a type of soil in the Arctic that holds an estimated 1.5 trillion tons of carbon (more than Earth’s atmosphere and forests combined) — is releasing both carbon and poisons, such as toxins and diseases, into the atmosphere. As this Arctic soil continues to thaw, it further accelerates climate change, creating a harmful cycle that will impact future populations.
To help fight climate change, farmers committed to sustainable agriculture, scientists, and researchers champion soil conservation, which promotes healthy, fertile, productive, and resilient soils. Soil conservation is essential for:
- Reducing climate change’s destructive impact worldwide
- Maintaining a balanced climate cycle
- Providing healthy ecosystems where plants, trees, and animals can thrive
- Ensuring healthy agricultural yields through sustainable farming practices
What is soil conservation?
Soil provides the nutrients essential for plant growth, animal life, and millions of microorganisms. However, if the soil becomes unhealthy, unstable, or polluted, the life cycle stops. Soil conservation focuses on keeping soils healthy through a combination of practices and techniques. Individuals committed to soil conservation help ensure that soil is fertile and productive, and protect it from erosion and deterioration. For more information about soil conservation please visit Pritish Kumar Halder
Threats to soil conservation
The primary threats to soil conservation are climate change and traditional farming practices, according to the United Nations. Traditional farming practices include the overuse of harmful pesticides that contaminate soils, slash-and-burn methods, and land overuse. Soil conservation aims to mitigate these threats.
The use of pesticides can contaminate the soil, as well as nearby vegetation and water sources, with harmful chemicals. In addition to contamination, chemicals used on crops can be toxic to important beneficial insects, such as bees, as well as fish and bird populations. According to a recent study about bird biodiversity in the U.S. published in Nature Sustainability, the grassland bird population has declined by 53% since 1970. Among the causes reported for this decrease is the growing use of pesticides.
Slash and burn
Such practices of burning and clearing forests make way for farmland. This method kills plant species and displaces wildlife from their natural habitats. Land cleared using slash and burn is only used while it’s productive for farming. Once it loses its fertility, another patch of forest is identified for clearing. This unsustainable process repeats endlessly, preventing soil from recovering sufficiently to support healthy ecosystems.
Overuse of land can limit soil’s ability to play its part in the global climate cycle. For example, overcutting forests and woodlands for timber and overgrazing pastures can far outpace the natural regrowth of vegetation, subjecting soil to increased exposure to erosion. As a result, land can lose its arability and become a desert.
Soil conservation is important for sustainability
For those working in sustainability, an understanding of soil’s role can create opportunities to develop new solutions and promote stewardship of our environment. Why is soil conservation important for sustainability? Simply put, without soil conservation, soil erosion would increase. Soil erosion impacts markets worldwide, including $8 billion in losses due to lower crop yields and increased water usage.
Why is soil important? Soil is essential to food production. Crops need soil to grow, and farm animals need vegetation for feed. Conserving soil can help address food insecurity and promote healthy communities. Soil also helps to create a cleaner climate, absorbing about a third of the carbon dioxide that fossil fuels and industrial operations emit, according to the Climate Change and Land report from the Intergovernmental Panel on Climate Change (IPCC). Healthy stewardship of soil can help mitigate climate change’s impact.
What makes soil so important?
Soils help meet societal needs, providing food, energy, and nutrients. They also help minimize the impact of climate change and promote healthy ecosystems.
Below are three reasons why soil is so important:
Home to many living things
Soil organisms ensure sustainable food systems and mitigate climate change. Plants and animals rely on soils for food, shelter, and more. Soil is also home to fungi, algae, and unicellular and multicellular organisms that are invisible to the naked eye, such as bacteria and protozoa. As they move through the soil, microorganisms help improve drainage and soil structure, making the soil more fertile and productive.
Key to the carbon cycle
The continuous process by which carbon atoms travel between the atmosphere and Earth. For example, in breaking down organic matter in the soil, microorganisms release carbon dioxide into the atmosphere and create nutrients and minerals that feed plants and crops. Soil also naturally absorbs carbon from the atmosphere in a process known as sequestration. Healthier soil absorbs more carbon, reducing the effects of greenhouse gases.
Soil’s essential roles
Farmers rely on soils to make food production possible, feeding people and livestock. Soil also acts as a purifier: As surface water travels through the ground to replenish aquifers, soil filters out toxins and impurities, making it drinkable. Soil also provides raw materials for infrastructure. For example, the soil is an important element in making bricks for buildings.
Benefits of soil conservation
Contributes to sustainability and offers the following benefits:
- Improves soil quality and productivity. Increased fertility improves crop yields, reduces the need for chemical fertilizers, and saves money.
- Optimizes water infiltration. Better filtration increases water storage, preventing soil from drying out.
- Provides food and shelter. Soil-producing vegetation provides nourishment to all types of animals and offers protection from the elements.
Soil conservation also helps to minimize the following:
- Loss of fertile and arable land, impacting crops and livestock production, as well as the economy
- Pollution and sedimentation flowing in streams and rivers, affecting fish and other species
- Erosion and environmental degradation and desertification of land, potentially increasing flooding and negatively impacting forest ecosystems
Soil conservation practices
It is a key to environmental sustainability: It helps protect natural resources and watersheds, restores habitats for plants and wildlife, improves water quality, and makes soil healthier. Soil conservation also creates economic opportunity. Productive and healthy soil helps farmers meet increased demand for agricultural commodities from a growing global population, driving economic growth.
Tilling turns over about 10 inches of topsoil and allows farmers to plant more seeds with less effort. A downside of tilling is that it removes the plant covering, potentially leaving the soil bare, decreasing the amount of nutrient-rich organic matter, and reducing its ability to absorb water and retain nutrients. Tilling can also make the soil more susceptible to erosion. In no-till farming, seeds are planted in narrow furrows, eliminating the need to plow.
Protects the soil from moisture loss due to high temperatures because cover crop residue remains on the surface of the soil. The residue layer also helps infiltrate water into the soil and increases organic matter and microorganisms, further enriching the soil.
This is an agricultural practice that uses terraces, or steps, built into the slopes of hilly or mountainous areas to create a water catchment system for crops and is commonly used in growing rice. Rainwater carries nutrients and vegetation from one terrace to the next, so the soil remains healthy. Terrace farming also reduces soil erosion and improves soil productivity in otherwise idle plots of land.
Like terrace farming, contour farming involves growing crops on hills, but instead of changing the structure of a hill, the farmer uses its natural slope. In contour farming, a farmer plows the soil parallel to the hill’s contours, creating rows of small dams that minimize runoff of essential nutrients, organisms, and plants, while increasing water infiltration in the soil. The U.S. Department of Agriculture (USDA) reports that contour farming can reduce soil erosion by as much as 50%.
Instead of planting the same crop year after year on the same plot of land, crop rotation involves planning out growing seasons for different crops. This method of sustainable agriculture requires long-term planning, with crops changing every season. In addition to improving soil health and organic matter, crop rotation reduces the need for fertilizer and pesticides, lowering costs. It also helps prevent excess chemicals from entering water supplies, improving water quality.
They are rows of trees and bushes planted between fields of crops, reducing the erosive power of the wind on the soil. Windbreaks also provide homes for living things. From an economic standpoint, using trees that produce fruits and nuts in windbreaks can diversify farm income.
The U.S. Environmental Protection Agency (EPA) defines wetlands restoration and protection as “removing a threat or preventing the decline of wetland conditions.” Wetlands provide a habitat for living creatures of all types. They also act as buffers, protecting farmlands from floods.
Like windbreaks, buffer strips are designated areas of land planted with trees and bushes. Instead of protecting soil from the wind, their purpose is to prevent water runoff and reduce erosion.
Forest cover reestablishment
In areas where the soil has degraded, the reestablishment of forest cover can improve soil and restore ecosystem health. This method provides shade for crops and is particularly useful for forest farming, which cultivates high-value crops, such as those used for medicinal purposes.
These are among the most productive organisms in the soil. They digest plant matter, releasing essential nutrients into the soil, and their tunnel networks create air channels that help water move through the soil.
Unsustainable agricultural practices can affect soil health, which in turn affects the global climate cycle. Poorly managed soil can release excess carbon dioxide, a greenhouse gas that contributes to climate change. Restoring degraded soil and using soil conservation practices in agriculture can effectively sequester carbon, helping build resilience to the effects of climate change.
Soil conservation also promotes sustainable and economic development to meet the U.N. Sustainable Development Goals (SDGs): 17 goals focused on providing a “sustainable future for all.” According to the European Environment Agency, seven SDGs directly correlate to soil conservation practices, including the following:
- Clean Water and Sanitation: from drainage and purification, soil helps to provide clean water for drinking and farming.
- Climate Action: Through sequestration, soil can play a pivotal part in combating climate change by reducing atmospheric carbon.
- Life on Land: Healthy soils are essential for the sustainable management of forests, fighting desertification, and reversing land degradation.
Building the resilience of our ecosystems is critical to addressing the challenges of a changing climate. One key factor sits right under our feet: soil. Through soil conservation, we can work to minimize the impact of climate change and support the long-term needs of society.
Many agricultural and industrial practices can threaten water quality if soil properties and capabilities are poorly understood or ignored. These threats are serious, but they also are manageable. Water quality can be improved while protecting the productivity and value of the soil for agricultural, industrial, and recreational uses. We can have both healthy soil and clean water by applying good soil management practices.