What measures 1 centimetre and takes about 300 years to form, sometimes much more, and sometimes less?
That's the planet's topsoil we're talking about.
You are probably used to seeing dark, deep layers of soil everywhere you look, from gardens to parks and alleys. Truth is that this fertile soil abundance is not a global commodity. It remains a resource that is easy to lose or degrade, especially because of intensive agricultural practices, urbanisation and pollution!
Soil Conservation Definition
Soil conservation represents the totality of the methods used to prevent soil degradation, specific to its geographical area and climate.
The main goal of soil conservation is to maintain or improve the productive capacity of the land by preventing soil degradation.
Soil degradation is caused by a number of factors, including:
wind and water erosion. E.g., on bare soils after maize and wheat harvesting
compaction. E.g., through heavy machinery used, especially tractors (as opposed to intentional soil compacting machinery, such as wheel rollers)
deforestation. E.g., to make space for housing, animal rearing, etc.
poor agricultural practices. E.g., insufficient irrigation, monocultures.
chemical changes. E.g., loss of phosphorous, pH differentials
Soil conservation includes contour plowing and leaving fields uncultivated to regenerate. In addition to preventing soil degradation, soil conservation also seeks to improve soil fertility by adding organic matter and controlling pests and diseases. By increasing the productivity of the land, soil conservation helps to ensure that future generations will be able to enjoy the benefits of a healthy and productive natural environment.
Soil Conservation Practices
Soil conservation efforts seek to address these problems through a variety of measures.
| Practice | Details |
Contour ploughing | - plowing along the contours of a field to create terraces, especially on 2-10% (gentle) slopes1
- slows down water streams, which can otherwise erode soil or dig trenches into it
- practiced historically in the UK, still practiced in places such as Coon Creek Watershed in Wisconsin (USA) or Grenada (Spain).
|
Crop rotation | - growing different crops in a field in different years.
- keeps the soil healthy by preventing nutrient depletion
- practiced historically by Greeks, Romans, etc. and still in use in rural areas of Italy, Greece, Romania, the Philippines, etc.
|
No tilling | - minimises the disturbance of the soil, does not necessarily improve soil aeration.
- helps to reduce soil erosion and improve soil health
- practiced extensively in South America in countries such as Argentina.
|
Cover crops | - planted between cash crops (the main crops that are grown for sale).
- plants fit as cover crops include the velvet bean Mucuna), Desmodium grasses, Aeschynomene plants, etc.
- helps to improve soil health by adding organic matter and preventing erosion
- used in areas of the world such as West Africa
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Terracing | - practiced in parts of the world with a lot of hilly and mountainous relief, such as Vietnam
- crops suited for terracing include rice, Camellia sinensis (from which green and black tea are made), grapes, barley, etc.
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Different soil types and their vegetation are affected by abiotic factors.
Without strong, direct sunlight, the baseline temperature difference between bare ground and ground covered in something such as straw can be 4 degrees C.2 In the direct sunlight of summer months, soil temperature differences between bare and covered ground can be larger than 10 degrees C.
Types of Soil Conservation
The most effective types of soil conservation depend on the type of soil and the type of ecosystem present!
The expectations of soil conservation in agriculture differ from the expectations of soil conservation in a protected primeval forest (forest with many centuries-old trees and other specific characteristics). Therefore, the land-use practices in place are very important.
Conserving Soil Mineral Qualities
All plants require a number of essential elements (nutrients) to grow and reproduce. 17 of these are essential, and while plants can always obtain elements such as carbon (C) and oxygen (O) from their environment, 14 of the essential nutrients they need are only found in soils and water. They include Zinc (Zn), Calcium (Ca) and Magnesium (Mg). These elements get inside soils through rock weathering, manures, dead biological matter, and other ways.3
As you can imagine, plants can use up these nutrients, which leaves the soils less productive!
Plants themselves end up being less nutritive if grown in impoverished soils.
Mud-puddling is the behavior displayed by a number of animals, especially insects, in which they gather on clay soils or similar to extract necessary mineral nutrients there present.
Bare Ground for Reptiles
It would be a mistake to think that only soil covered in rich vegetation can be useful or beneficial. Many reptile species prefer to bask in the sun on riverbanks, on those sandy soils. These soils get hotter than surrounding vegetation, which is ideal for their body temperature needs. Moreover, since reptiles tend to grow long but not tall, vegetation blocks their field of vision, and renders them more vulnerable to predators.
Common lizards Zootoca vivipara are hunted by common kestrels (Falco tinnunculus).
Encouraging Mycorrhizae
Mycorrhizae (plural) are different types of fungi that associate themselves with plants in a symbiotic relationship.
The fungus helps plants absorb certain nutrients such as phosphates and act as extensions for roots, even sending chemical signals between each other. In return, the fungus gets carbohydrates (sugars) from the plant.
Mycorrhizae are sensitive to certain pesticides or excess fertilisers, and are thus affected by unsustainable soil practices.
Importance of Soil Conservation
Soil is important because it is one of those resources that takes a long time to form! When erosion occurs, soils are washed away or removed by wind and water. Conserving soils means avoiding the negative effects of soil erosion, such as waterway sedimentation, or loss of food resources.
Generally, soil forms slowly over hundreds, thousands or even millions of years. In some cases, soil can form quicker.
Soil forming in volcanic ash can form in just a few days.
Soil conservation also means protecting soil biota. Soil biota, which includes nematodes, spiders, ants, plants, algae, fungi, moles, shrews, etc., usually help aerate soils, reduce erosion and provide nutrients to soils.
Soil erosion causes damage around the world. A 2019 study estimated that water erosion suffered by agricultural soils costs the industry 8 billion US dollars.4
Advantages of Soil Conservation
General advantages of soil conservation include improving water quality, decreasing pollution and sedimentation in waterways, reducing greenhouse gas emissions, helping combat climate change, improving agricultural productivity, enhancing biodiversity and protecting endangered species.
The main advantage we will be starting with is soil conservation improving water infiltration, filtration through sediments, and water storage (in aquifers, groundwater).
Survivalists often show how to build a water 'purification system' using sand, charcoal, gravel and small rocks in a bottle.
Next, long-term soil quality for food growing is ensured by avoiding soil contamination through erosion, or the loss of essential nutrients and moisture.
Habitats and shelters are made in and out of soils constantly.
Think of all the soil biota and where it lives and add to that the animals that frequently burrow to raise young or sleep, from foxes, to hedgehogs, badgers, crocodiles, otters, and even bears, to hibernate!
For some of these animals, the soil they use needs to retain specific properties, such as thermal properties or aeration.
Carbon sequestration is something nature has been doing for a while with soils, and human are following suit.
Bogs, peat and swamps or the permafrost are critical areas of the Earth with high capacity for carbon storage. The modern world has drained numerous swamps and climate change is slowly melting the permafrost (frozen topsoil), leading to the release of even more CO2 into the atmosphere.
Detritivores, Decomposers and Recycling
Detritivores are organisms such as beetle larvae or slugs that eat organic matter and break it into smaller constituent elements for plants, bacteria, etc. to use. They internally digest their food.
Decomposers, on the other hand, are classed as organisms such as fungi who can break down dead organic matter via external digestion.
Last but not least, what happens with dry and eroded soil? Well, it may as well turn into sand. Soil conservation helps prevent desertification.
Arid parts of the world such as the Sahel (the transition area between the Sahara desert and the more humid, lush-green vegetation areas) need to protect against ongoing desertification due to overgrazing and deforestation. Soil can be eroded quickly due to high temperatures and sands can cover large areas fast, rendering them unusable for agriculture.
Disadvantages of Soil Conservation
One disadvantage of soil conservation is that it can be expensive. Methods like terracing require significant upfront investment, and cover crops might need to be purchased each year, when autochthonous production is scarce. In addition, soil conservation requires ongoing maintenance.
Another disadvantage of soil conservation is that it can take away from other uses of a piece of land.
Terracing can prevent steep slopes from being used for recreational activities such as hiking or skiing.
Soil conservation can have negative impacts on crop yield and soil quality in the short term, which may discourage farmers from implementing these practices. However, it is important to note that soil conservation is essential for long-term agricultural productivity and food security.
Medieval or ancient soil patches created and used by people are sometimes called anthroposoils or anthroposols and may still present elevated phosphate and nitrogen levels in modern times.5
In conclusion, it is clear that soil is a key part of our planet’s long-term health and sustainability. By using one or more of the methods presented and reducing the practices that take away from soil quality, farmers can help to keep the soil healthy and productive for future generations.
Soil Conservation - Key takeaways
- Soil degradation can be caused by wind and water erosion, compaction, loss of minerals, chemical changes, and many others.
- Soil conservation methods include contour ploughing, crop rotation, polycultures, agroforestry systems, etc.
- Soil conservation depends heavily on the ecobiological needs of the targeted area, such as bare ground needed for reptiles, certain soil nutrients for insects, an extensive mycorrhizae network for old plants, etc.
- Soils can take thousands of years to form in layers thicker than a few centimetres and this is why it is extremely important to prevent erosion.
- Advantages of soil conservation include habitat protection, food security, animal and plant conservation or climate change mitigation.
References
- Mark Otieno, What is contour farming?, 2018
- Soil health nexus, Soil temperature, 2019
- Balwant Singh & Darrell Schulze, Soil minerals and plant nutrition, 2015
- Martina Sartori et al., A linkage between the biophysical and the economic: Assessing the global market impacts of soil erosion, 2019.
- RECARE, Olden Eibergen Case Study, The Netherlands, 2018
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