Soil conservation mainly refers to the prevention of soil erosion from the uppermost layer of soil, as well as the prevention of acidification, salinization or other types of chemical contamination of the soil. Soil conservation also works towards the prevention of reduced soil fertility, often caused by over usage.
Soils are critical to life on earth and provide many of the nutrients required for life to exist. Plants convert the sun’s energy, along with carbon dioxide and water, into simple sugars that can be used for plant growth - but this process also requires essential plant nutrient elements which are found in the soil. Without these essential nutrients, plants wouldn’t have the right ingredients to grow properly, which would ultimately cause a collapse of the food chain.
The role soils play in our lives is often understated as we really wouldn’t be alive without them. That’s why it’s so important to maintain the health of the soil and prevent soils from being lost to erosion or to becoming depleted of vital nutrients. Let’s look at some of the methods used in soil conservation:
Soil-Conservation Farming
Global food production is key to human survival, so it only makes sense that we start looking at soil conservation practices in the areas where its most likely to be a problem. Farming has evolved over time from small-scale subsistence farming (growing food for personal / family or local use) to large-scale farming, which can produce enough food to feed large numbers of people.
One practice of soil-conservation farming is called no-till faming, which as the name implies, is a method of growing that does not use turned soil, which is much less disruptive to the soil and the microorganisms living in it. With no-till farming, growers attempt to mimic the biology of the natural landscape. This practice can help minimize soil erosion, help revitalize depleted soils, reduce the need for nitrogen fertilizers and pest control agents, as well as encourage plant growth. When soils are maintained in this way, crops are also better protected from the affects of flooding and / or drought.
Crop Rotation and Cover Crops
Crop rotation is important for the longevity of the soil. Monoculture (growing the same crop in the same location year after year) can cause certain essential plant nutrient elements to be depleted quickly, as the plants grown require the exact same types and amounts of nutrients every year, thus depleting the soil of these critical elements. By planting cover crops between growing cycles and switching crops more frequently (polyculture), growers can reduce the annual demand for some of the essential soil nutrients, which can then be replenished by the cover crops that act like sinks for nitrogen and other key nutrients. Cover crops are generally ploughed into the soil during field preparation and increase the amount of organic matter in the soil.
Windbreaks
One of the most common causes of soil erosion is wind. As the molecules of air whip over the surface of the soil, the soil particles can be lifted and pulled into the air steam, where they are carried away. Planting trees in dense rows at the windward exposure (often the western exposure) can greatly reduce the speed the wind is moving at across the land, decreasing the amount of friction at the surface soil level that would otherwise disrupt and displace the soil.
Contour Ploughing
Contour ploughing is a practice that has been utilized for thousands of years. The ancient Phoenicians were probably the first civilization to use this practice to not only increase crop yields, but also to improve soil retention. Contour ploughing works by orienting the furrows along the natural contour lines of the farmland, which is particularly helpful on sloping land (up to around ten per cent slope). The furrows move left and right and help prevent water runoff, while maintaining a constant altitude.
Terrace Farming
Similar in some ways to contour farming, terrace farming is practiced in sloping, hillside areas. Terraces give the appearance of steps up the hillside and each terrace is higher in elevation as you move up the hillside. More commonly found on small farming operations, terrace farming can help prevent soil erosion due to the soil barriers between the terraces.
Keyline Design
A practice similar to contour farming is Keyline design, which is an enhanced version of contour farming where the entire watershed properties are taken into consideration when forming the contour lines.
Salinity Management
Soils can become saline (salty) though irrigation using salty water. As the water evaporates at the surface of the soil, the salt that was dissolved in the water is left behind. Over time, the concentration of salt in the soil increases, leading to a breakdown of the soil structure, which ultimately leads to reduced soil fertility and reduced plant growth. Very few species of plants can survive in highly saline environments.
Mineralization
Sometimes when essential nutrients are depleted from soils, they can be replenished by nature or humans by mineralization. Mineralization can include adding certain minerals back into the soil. These minerals can come in the form of crushed rock, like limestone, which contains high levels of calcium carbonate and some magnesium. Some other minerals that may be added to the soil to repair nutrient depletion are phosphorus, selenium and zinc. In flood zones like alluvial plains, water can carry sediments that are rich in minerals and other nutrients, which are deposited on the existing soil, adding the additional minerals to it.
Soil Organisms
Some organisms found naturally in the soil aid in soil health and fertility. Earthworms for example excrete feces called casts. These casts contain a balance of nutrients and minerals that are in a form that is easily accessible for plant roots to uptake. Earthworm casts typically contain much higher amounts of available nitrogen, phosphates and potash than the surrounding 150 millimeters of the upper soil layer, making their contribution to soil health highly valuable.