Soil facts

As part of the activities of the International Year of Soils, FAO has published the following Soil Facts. Contribute with your comments!


The current rate of soil degradation threatens the capacity to meet needs of future generations.


We need healthy soils to achieve our food security and nutrition goals.
Did you know that a tablespoon of soil has more micro-organisms than the whole human population on Earth?


Multiple roles of soils often go unnoticed.


Our soils are precious. Did you know it can take up to 1,000 years to form 1 cm of top soil?


Soils are key in the global carbon cycle. They help us to mitigate and adapt to the climate change.

Eric Brevik’s work awarded by Geoderma

The review paper The use of electromagnetic induction techniques in soils studies, by James A. Doolittle and Eric Brevik, has been awarded as the Geoderma’s Best Review of 2014. The Geoderma Best Paper Awards are chosen every year since 2013. Candidates are nominated by the Geoderma Editorial Board and a short-list is then created for voting by the editorial Board. The winner of the Geoderma Best Paper Award receives 1 year promotional access to the paper, a certificate and a gift voucher. This paper and the rest of winning articles are freely available until July 2016. Continue reading

Turning unproductive soil into profits

Preeti Roychand

La Trobe University
AgriBio Centre for AgriBioscience
Melbourne, VIC, Australia

Sandy soils in Western Australia are bad soils for growing plants due to their poor nutrients and water holding capacity (see an example in Figure 1). In general, these soils are water repellent, which leads to land degradation by increasing soil erosion risk and run-off rates. Nevertheless, these soils may be improved by clay addition, which leads to increase soil organic carbon content (Franzluebbers et al. 1996). Several ways have been used to increase soil organic carbon content in soils: i) no-tillage systems, ii) addition of bio char , iii) organic amendments or fertilizer addition and iv) switch to perennial plants. But there is another potential method for enhancing soil organic carbon storage in soils which has received little attention: mixing of isolated clay with sandy soils. Continue reading

Fire and soil microorganisms: where should we focus on?

Gema Bárcenas-Moreno
University of Seville, Sevilla, Spain

Currently, the complexity of soil microbial ecology on soil systems is a hot topic in the environmental sciences, since the scientific community has achieved a deep knowledge of the relevance of microorganisms in soil processes. After several decades of study of the effects of wildfires on soils, one of the main conclusions is that soil microbial populations are very sensitive to fire, which allows us to use them as a tool to assess the impact of fire on ecosystems.

Polysaccharides distribution due to microbial colonization in a soil microaggregate. Credit: Imaggeo/Maria Hernandez-Soriano. Click the image for more information.
Polysaccharides distribution due to microbial colonization in a soil microaggregate. Credit: Imaggeo/María Hernández-Soriano. Click the image for more information.

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Soil science, food production and hunger in Africa

A child dies from malnutrition or related causes every five seconds. Every child who dies from hunger is assassinated. And we have a herd of market traders, speculators and financial bandits who have turned wild and constructed a world of inequality and horror. We have to put a stop to this.

Jean Ziegler

Soil as a resource

A long history of land use

Ever since man learned to cultivate, soil has been considered as a source of food for humanity. Agriculture was born during the Neolithic period, when the economy of human societies evolved from gathering, hunting and fishing to farming and ranching. The first known crops were wheat and barley. Cultivation of cereals and legumes favored the development of the population during the Neolithic, and the development of agricultural techniques such as the use of domesticated animals, irrigation, or intensive farming encouraged the development of civilizations in the Fertile Crescent, Egypt, India, China or America. In the West, improved cultivation techniques favored the development and expansion of agriculture during Roman times and the Middle Ages, further improving the living conditions of farmers. Especially since the discovery of America (AKA collision against Europe), globalization of agricultural products initiated.

Fruits and vegetables in the Mercado Libertad, in Guadalajara (Jalisco, Mexico). By A. Jordán. Click to see the original picture at Imaggeo.

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Snow deposits: A soil disturbance in urban areas

Snow stores a great amount of sediments during the winter. After this season snow melt transports a large amount of sediments to floodplains and water bodies. This natural process depends of the land-use, and is accelerated in urban areas, due soil sealing, which facilitates runoff and sediment transport. Here, sediments very often contain a high amount of sodium, due the salt spreading in the roads to break the ice. These sediments with high levels of sodium can induce an additional disturbance in the place where they are deposited. When leached into the soil, they will contribute to soil clay dispersion, sediment production and the increase of erosion potential. In urban areas as Vilnius, Lithuania (Figure 1), the sediment produced after the snow melt is a problem for the municipality and a cause of soil degradation in urban areas.

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Figure 1. Snow Deposits in urban parks.

Soils at Imaggeo: Badlands in central Spain

Saskia Keesstra, Wageningen University, Wageningen, The Netherlands

Badland in central Spain. Click on the image to see the original picture and details at Imaggeo.
Badland in central Spain. In the image, Ana Lucía Vela (Free University of Bolzano-Bozen, Italy).


This composite shows a constellation of combined visual and infrared imaging of a smouldering combustion front spreading radially over a thin sample of dry peat. The central watch is created by a series of twelve wedges. Each wedge is extracted from a photo taken every 5 min from an elevated view looking down into the sample during the one-hour lab experiment. The circular peat sample (D=22 cm) was ignited on the centre by an electrical heater. The average radial spread rate was 10 cm/h and the peak temperature 600°C. The top figures show the virgin peat (left) and the final residue (right). The bottom figures show the wedges in visual (left) and infrared (right) imaging. Smouldering combustion is the driving phenomenon of wildfires in peatlands, like those causing haze episodes in southeast Asia and Northeast Europe. These are the largest fires on Earth and an extensive source of greenhouse gases, but poorly studied. Our experiments help to understand this emerging research topic in climate-change mitigation by characterizing the dynamics of ignition, spread and extinction, and also measure the yield of carbon emissions.

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