Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Record summer causing long-term damage to soil – herbicide degradation poorer after drought

04.09.2006
Heat records and continuing drought like in the summers of 2003 and 2006 make not only plants dry up, but they can also cause long-term damage to soils. This was found by scientists from the GSF Research Centre for Environment and Health, who are engaged in a long-term test investigating the ability of soils to degrade the herbicide isoproturon.

“Since 1997 we have been observing four outdoor soils,” explains Dr. Reiner Schroll (Institute of Soil Ecology), “we were essentially concerned with the question how isoproturon behaves in different soils as a model substance for pesticides.” Until summer 2003 one of these soils degraded isoproturon particularly efficiently: the microorganisms living in the soil mineralised up to 60 per cent of the isoproturon applied within approx. two months.

After the drought in summer 2003, however, the degradation capacity of this soil dropped dramatically. In particular, there was only very little degradation in the top few centimetres. “Drought and heat resulted in very profound changes in the composition of the microbial communities (biocoenosis), which could not even be reversed by extended remoistening of the soil before the investigations were carried out,” Schroll explains the drastic reduction. On the one hand the absolute number of microorganisms dropped, on the other the composition of species changed: apparently the bacteria degrading isoproturon in particular were so badly damaged that they had practically become extinct in the top soil.

The soil has still not recovered completely up to this day: new investigations in April 2006 showed a degradation capacity of only 15 per cent of the isoproturon applied. “Our results show how important long-term experiments are,“ Schroll emphasizes, „it was only when we compared the degradation capacity over several years that we noticed the changes.”

To make a comparison of the degradation capacity beyond vegetation periods possible at all, the various soils have to be analysed in identical weather conditions. In particular the soil water content is of central significance, since it influences the air-oxygen supply to the microorganisms on the one hand, and on the other determines the supply with nutrients and chemicals to be degraded, such as pesticides. Therefore, all soil samples were moistened before the tests in laboratory experiments. It is not the absolute water content that is decisive for the microbial activity, but the water tension, i.e. the force which retains the water in the soil. It had, however, not been known up until now at which water tension the optimum degradation of substances can be expected, so that this water content had to be determined empirically for each soil individually.

While they were conducting these tests, the GSF scientists made yet another very interesting discovery: “Irrespective of the type of soil and the substance to be degraded, the maximum microbial degradation activity always developed at a water tension of -0.015 Megapascal – this value seems to be a natural constant,” Schroll emphasizes. At this water tension, e.g., the soil microorganisms only have to exert a suction of approx. 0.15 millibars, in order to take up water from the soil – microorganisms love a moist environment.

Schroll’s results are particularly relevant, e.g., for the environment in the conurbation of Munich, since one of the soils investigated is a typical agricultural soil, as it is representative for large areas of the Munich gravel plain. When herbicides can no longer be degraded properly there, they can be shifted downwardly more easily and may enter the drinking water. Ploughing could be a countermeasure to this: since the lower soil layers are not affected as badly by the drought, mixing the soil may help, in order to settle the respective microorganisms in the top soil areas again. “For very badly damaged soils the deliberate introduction of suitable microorganisms might also be a possibility,“ explains Schroll, „both measures, however, are more labour-intensive and slightly more expensive than the minimum tillage, which is increasingly applied in agriculture. But if the weather fluctuations with their various effects continue to intensify – and estimates made by colleagues very strongly suggest this – science and agriculture will have to respond with appropriate countermeasures. Unfortunately climate change is a fact, and we have to face it.”

Michael van den Heuvel | alfa
Further information:
http://www.gsf.de/neu/Aktuelles/Presse/2006/schroll_en.php

More articles from Ecology, The Environment and Conservation:

nachricht Reducing household waste with less energy
18.01.2017 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH

nachricht Joint research project on wastewater for reuse examines pond system in Namibia
19.12.2016 | Technische Universität Darmstadt

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>