The Horse 2020/21

Full article in English and German (ethz.ch)

Soil organisms both serve as a source of nutrients for plant growth and drive the transformations of nutrients that make them available to plants. The collective carbon content of all soil bacterial cells is comparable to that of all plants on earth, and their total nitrogen and phosphorous contents are far greater than that of all vegetation, making these microorganisms the primary source of indispensable nutrients for life. Plants fix carbon from the atmosphere, but they require macro and micronutrients that are absorbed from the soil to create biomass and transfer nutrients and energy. Soil microbes and microfauna interact with abiotic factors – temperature, pH, moisture content- and drive these transformation processes. Soil micro, meso and macrofauna play a key role in the physical breakdown of plant residues, allowing the soil microorganisms to liberate the nutrients and energy bound up in the plant material. The role of soil organisms in agriculture has many beneficial effects beyond plant nutrition. For example, soil microbiota such as arbuscular mycorrhizal fungi and nitrogen fixing bacteria can minimise cost and dependence on synthetic nitrogen fertilizers in agriculture, and enhance soil fertility and environmental sustainability, including reducing greenhouse gas emissions from the energy-intensive manufacture of nitrogen fertilizer.

The role of soil biodiversity in addressing global climate change cannot be understated: the soil community’s activities can contribute either to the emission of greenhouse gases or to absorbing carbon into soils from the atmosphere. As part of the natural functions and ecosystem services provided by soils, a healthy soil stores more carbon than that stored in the atmosphere and vegetation combined. Carbon is either fixed or released from soils, depending the activity of the soil organisms and driven by soil conditions. Carbon is fixed into soils through the transformation of plant and animal detritus, and also some bacteria and archaea can fix carbon by using atmospheric CO2 as their energy source. Beyond their direct role in the carbon cycle, soil organisms are also critical for efforts to reduce overall greenhouse gas (GHG) emissions from agriculture. Globally, agricultural ecosystems contribute 10 to 12 percent of all direct anthropogenic GHG emissions each year, with an estimated 38 percent resulting from soil nitrous oxide emissions and 11 percent from methane in rice cultivation. Soil microorganisms are involved in every step of nitrogen and carbon transformations that yield these greenhouse gases, and managing the soil environment to minimise emissions is a key objective in sustainable soil management.

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Sources:
learning.edx.org

http://www.fao.org/

EDX 4.3 Soil Biodiversity Characteristics

Soil biodiversity is the variety of life that exists within the soil, including bacteria, fungi, earthworms, and termites. A teaspoon of topsoil typically contains a vast range of different species and up to 6 billion microorganisms.

The group of large organisms in the soil is visible to the human eye. (Macroscopic)
For example:

• Plants
• soil fauna
• worms (earthworms, pot worms)
• isopods, millipedes, centipedes

The group of small organisms in the soil isn't visible to the human eye. (Microscopic)
For example:

• Soil microbes - bacteria, fungi
• microfauna (nematodes)

If we take a look at an arable field or a grassland then we see, aboveground, a few plant species: one plant species in a monocrop and up to 50 species per square meter in species-rich grassland.

Now if we look at the number of different species or the diversity, we can see the smaller the organisms the more different species there are, ranging from 10 species of earthworms to thousands of species of bacteria and fungi.

Soil life is sensitive to disturbance and compaction of soil because that affects the amount of space and air available for plant roots and other soil biotas.

It is also sensitive to chemicals that end up in the soil water, or pollution like oil spills that block access to food, air, and water. Life in soil is also sensitive to temperature and soil acidity.
Soil organisms feed directly or indirectly on plant inputs and not all species like to eat the same thing. So the type of plant you grow, like the type of crop or green manure that you add to the soil, can all influence the abundance and diversity of the soil life.

What is salinization? 

That is the level of salts or salt content in water or soil.  
A lot of salts do we leach out or wash out of our body with sweating or with peeing. 

But how do those salts come into the soil?  
There are two different ways of that. 

The first one is natural salinization. Where the water picks up salts from weathering rocks. 

The second one is human-induced salinization, when the water, in which the salts are dissolved, is used to irrigate a crop. This crop only uses the water and, unless there is adequate drainage, the salts are left behind in the root zone. 

There are as well two different classifications of soil salinity. 
The first one is the saline soils. Those are the total salt levels in soil that are harmful to plant growth. 
The second one is the sodic soils. Those are sodium salt levels that have a negative effect on soil and plant health. 

What is soil pollution?

- When the concentration of pollutants on the surface becomes so high that it harms land biodiversity and endangers health (particularly through food)

- Farmers use chemicals, pesticides and fertilisers that pollute the land

- A gobal threat (particularly serious in regions like Europe, Eurasia, Asia and North Africa)

- It's already affecting one third of the world's soil

Causes and types of soil pollution

Erosion, loss of organic carbon, increased salt content, compacting, acidification and chemical pollution are the major causes of current soil degradation

Specific pollution: accounted for by particular causes, occurring in small areas the reasons for which can be easily identified. Land pollution such as this is normally found in cities, old factory sites, around roadways, illegal dumps and sewage treatment stations.

Widespread pollution: covers extensive areas and has several causes the reasons for which are difficult to identify. Cases such as these involve the spreading of pollutants by air-ground-water systems and seriously affect human health and the environment.

Consequences of soil pollution

Damage to health

Soil pollutants enter our body through the food chain, causing illnesses to appear. Moreover, the spread of antibiotics in the environment increases the pathogens' resistance to these drugs.

Poorer harvests

Soil pollution agents jeopardise world food security by reducing the amount and quality of harvests.

Climate change

In the first decade of the 21st century, soil degradation released between 3.6 and 4.4 billion tonnes of CO₂ into the atmosphere.

Water and air pollution

Soil degradation affects the quality of air and water, particularly in developing countries.

Population displacement

Soil degradation and climate change will have driven between 50 and 700 million people to emigrate by 2050.

Species extinction

Soil contamination is one of the main causes that could trigger the sixth mass extinction event in history — the population of land vertebrates fell by 38 % between 1970 and 2012 —.

Desertification

The number of inhabitants in the most arid areas of the earth could account for 45 % of the world's population in 2050, while world wetland areas have decreased in size by 87 % over the last three centuries.

Economic impact

Global economic losses caused by soil degradation are expected to exceed 10 % of the world's annual Gross Domestic Product (GDP).

Solutions to reduce soil pollution

- Eat sustainable foodstuffs, properly recycle batteries, produce homemade compost and dispose of drugs in the places authorised for this purpose.

- Encourage a more eco-friendly model for industry, farming and stock breeding, among other economic activities

- Improve urban planning and transport planning and waste water treatment.

- Improve the management of mining waste, restore the landscape and conserve topsoil.

- Involve local communities and indigenous peoples in the design, implementation and assessment of sustainable land and soil management.

Source
[1] What is soil pollution?
[2] Introduction soil pollution

Were you aware that:

• China and India are losing soil 30 to 40 times faster than the natural soil replenishment rate allows it
• 400 billion Dollars per year is the estimated damage of soil erosion worldwide
• 30% of the world's arable land has become unproductive due to soil erosion over the past 40 years
• About 60% of soil that is washed away ends up in rivers, streams and lakes
  • This increases the danger of waterways overflooding

Together, wind and water erosion account for 84% of all land degradation making them the biggest danger for future food planting.

[in progress]

With the help of edx.org we learned more about Sustainable Soil Management. We found the course (Module 7) which talked about soil pollution interesting. In this module, we learned about a distinction between point pollution and diffuse pollution. We also learned about the main sources of soil pollution, how different pollutants behave in the soil and why it is important to know about natural background levels of heavy metals in soils.

There are many different sources of soil pollution. Some main sources are industrial sources, urban sources as waste and traffic, and agricultural sources. These sources all release pollutants and these pollutants are then mostly transported in three different ways.

The first one is via air. Transportation via air is a very widespread, long range transport and it can be carried over thousands of kilometres to other places. The pollutant which are in the air are then deposited by rain fall, snow, or by dry position as particulates into the soils.

The second next important transport way is water. If waste water is not sufficiently cleaned, it ends up into the rivers and is there transported over thousands or hundreds of kilometres to many different cities and many even countries.
Could you imagine what would happen when dirty water would be used to water agricultural soils or what would happen if dirty rivers would overflow?

The third transportation way is a more direct pathway and that is land deposition. This means Pollutants can be directly deposited on land.

But the big question is how organic pollutants get into the soil and into our plants and into the water in the soil?

The answer this question, you need to imagine these pollutants are deposited on the soil and it rains afterwards. If this takes place on a smooth slope or a bigger slope, these pollutants can be transported with the rain water and end up into lakes and rivers downstream. What can also happen is that the pollutants can be transported in the soil water and can enter “clean” ground water sources.

Another thing that can happen is that the pollutants remain in the soil. This depends on the properties of the pollutants. Pollutants can be strongly adsorbed by the soil and they remain there for many years, depending on their decay. Organic pollutants undergo different durations of decay and these decays can vary between several hours and decades of years.

We hope you learned something new and interessing just as we did :)

Kind regards, Cindy & Alexa

Links: learning.edx.org

Evidence underpants - Beweisstück Unterhose (beweisstueck-unterhose.ch)
Citizen Science project (pwa.uzh.ch)

Explore the soil life in your field, garden, or in front of your house

Materials in German
Anleitung_eigene_Unterhosen_deutsch.pdf (2.74 mb)
Anleitung_Zusatztest_Bodsenanalysen_Layout_De_1.pdf (269.31 kb)

What is water erosion ?

Water erosion is the removal of the top layer of land by water from irrigation, rainfall, snowmelt, runoff, and poor irrigation management. Ultimately, rainwater is most frequently to blame when it comes to this issue. The flowing water moves the soil organic and inorganic particles alongside the land surface, depositing them in the lower landscape. The result of this would be flooding in the long run. The eroded soil material can either form a new soil or move to water reservoirs nearby.

Different types of water erosion

splash erosion

This is the first stage in the erosion process that is caused by rain. Raindrops basically “bombard” the exposed and bare land, moving its particles and destroying the structure of the top layer.

sheet erosion 

This type of soil degradation by water occurs when the rainfall intensity is greater than the soil infiltration ability and results in the loss of the finest soil particles that contain nutrients and organic matter.

rill erosion 

Rill erosion follows after, when the water concentrates deeper in the soil and starts forming faster-flowing channels. These channels can be up to 30cm deep and cause detachment and transportation of soil particles.

gully erosion 

This is an advanced stage of land damage by water when the surface channels are eroded to the extent when even tillage operations wouldn’t be of any help. 

tunnel erosion

This is the so-called “hidden” type of land degradation by water that can cause severe disruption even before any signs are evident to the eye. It begins when large water mass starts moving through the structurally unstable soil.

What Are The Negative Effects Of Water Erosion?

Flooding 
Severe land degradation by water can negatively impact the ecosystems  by causing flooding. The washed away topsoil loses its water absorption ability, greatly increasing the possibility of flooding in areas that are predisposed to it. It could be low-lying landscapes and soils with limited drainage ability. Ultimately, heavy flooding can be extremely disruptive to the extent of ruining roads and buildings. That is why it’s critical to spot negative changes in farmland health to prevent the situation from getting to that point.

Impact of water quality
Apart from affecting animals, plants, and farmland, water erosion also significantly decreases the quality of water itself. The particles of the eroded soil eventually reach the water sources nearby, changing the water chemical content and reducing its oxygen levels. Besides, the water from eroded farmlands contains harmful chemicals (due to previous pesticides application), washing them off to lakes, streams, and rivers.


How to stop water erosion and its management 

Water erosion control is vital in battling the issue of land degradation caused by water. And the
water erosion solutions differ depending on the , topography, climate, crop rotation, and land use. However, there are water erosion prevention measures for its every type.

QUIZ 

Which of these different types of water erosion does not exist?

a) splash erosion 
b) sheet erosion 
c) rill erosion 
d) gully erosion 
e) tunnel erosion 
f)drill erosion 

Source

eos.com

written by Leandro and David