Soil scientists in Germany have made a breakthrough in their understanding of how healthy soil is formed. They found that the remains of dead bacteria, which build up in fertile soils, play a much greater role in soil health than had previously been assumed.

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Researchers from the Helmholtz Centre for Environmental Research (UFZ) in Liepzig, conducted laboratory and field testing to demonstrate that healthy soil is created when plant material is converted into microbes, which then die and form the source material for soils.  

The discovery, which comes less than a month after World Soil Day attempted to raise the profile of this most important resource, opens a new avenue of research for soil scientists; before the UFZ researchers and their international colleagues, began their research, it was assumed that soil was mostly comprised of decomposed plant matter, and less focus was placed on bacteria and fungi. http://www.farming.co.uk/news/article/7638

They said their research has implications for climate change research, as well as agrology because soils are the largest land-based carbon sink on Earth. The researchers said "Climatic change can therefore be slowed down or accelerated, according to the management of the soil resource."

Miniscule parts of dead bacteria were found throughout soils examined by the UFZ researchers; they said these had been discovered in previous studies, but not fully understood or investigated. Their findings relating to the bacterial matter in soils led them to understand some important factors of soil degradation and regeneration.

Field test confirms laboratory findings

In summer of 2009 the researchers took soil samples in the forefield of the Damma Glacier in the Swiss Canton Uri. In the course of the last 150 years glacier has retreated by around one kilometre. In its place granite rock remained behind, which was gradually recolonised by living organisms accompanied by soil development. Following the formation of new soil the first plants, such as mosses and grasses, were followed by bushes and, later, also by trees. In the meantime, the Damma Glacier has therefore become an important outdoor laboratory not only for climate researchers, but for ecologists as well.

The soil sampled by the researchers was between 0 and 120 years old and thus allowed insight into early processes of soil development. They found more bacterial residue in older, more stable and fertile soil.

The researchers summarised, "The predominant share of the plant debris in fertile soil is thus rapidly processed by micro-organisms, e.g. bacteria, leading to more bacteria and, in turn, also to more cell fragments. This then results in more organic material in the soil."

Lead author Matthias Kästner said, "Even though the greatest part of the organic carbon in the eco-systems is definitively produced primarily by plants, we were able to show that a large part of the organic material is actually comprised of residues of bacteria and fungi. This underscores the importance of bacteria as organisms in all types of soil".

Results show significance of soils

The researchers reiterated the importance of their findings to climate scientists as well as agricultural researchers; they said degradation of these organic materials results in mineralisation and the release of carbon dioxide, a potent greenhouse gas.

According to estimates from Great Britain, the amount of CO₂ escaping annually to the atmosphere due to the degradation of organic material in soils in England and Wales alone is comparable to the annual reductions in greenhouse gas emissions made elsewhere in the country. The researchers concluded "This means that no rigorous progress in climate protection may be accomplished without first protecting the soil."

Earlier this week, researchers conducting a Brown University-led study of three soybean growing regions, including Brazil, Argentina and the United States, said that, their research, which looked at plantations on former rainforest land requiring significant fertiliser inputs, as well as fertile US soil which had been over-fertilised, showed "soils [in these areas] have taken on a new role: mediating the environmental consequences of modern farming." http://www.farming.co.uk/news/article/7709