Acidified cattle slurry's effect on springtails investigated
Researchers at Aarhus University have investigated the effect of acidified cattle slurry on springtails - an indicator of soil quality.
Acidification of cattle slurry with sulfuric acid before application in a crop is an important measure to reduce the volatilization losses of ammonia. Acidification increases the fertilizer value of the slurry and reduces the impact on the environment. However, what about the impact on soil organisms?
Researchers from the Department of Agroecology and the Department of Bioscience at Aarhus University exposed collembolan communities (springtails) to acidified slurry in a comprehensive laboratory experiment. Like earthworms and many other soil organisms, springtails play an important role in the turnover of organic matter in soil - be it plant residues or animal manure. Since springtails are often used as test animals in ecotoxicological studies, the researchers took advantage of this experimental set-up to test the effects of acidified slurry.
Previous studies on the effect of manure on soil organisms show contradictory results. Livestock manure provides food for the small animals, but an excessive concentration of ammonium can also have a negative effect on the springtails.
“It was important for us to investigate whether the use of slurry and not least acidified slurry could have a negative effect on the biological quality of the soil. Here we could use the springtail test, which our colleagues from biology have a lot of experience with,” Professor Bent Tolstrup Christensen from the Department of Agroecology at Aarhus University says.
Two ways of applying slurry
Springtails can be divided into three functional groups, depending on where they typically reside: on the soil surface (epedaphic), just below the soil surface (hemiedaphic) or at greater soil depths (euedaphic).
“Our test group of springtails consisted of two species from each of these three groups. They were released into soil mixed with slurry, untreated or acidified. Thereby we were able to cover effects of acidified slurry on springtails at different depths in the soil. We added two rates of slurry - one corresponding to surface-applied slurry and one corresponding to slurry residing in slits after injection tines,” Bent Tolstrup Christensen explains.
When slurry is injected, the soil around each injection slit can have a high concentration of ammonium, and by acidification this concentration will be maintained for a longer period until the plants are allowed to use the ammonium supplied. Both types of application are commonly used, which is why researchers found it necessary to investigate both methods.
After 28 and 56 days of incubation, the research team extracted the springtails and determined the number of young and adult individuals to assess the effect of the acidified slurry.
Is slurry good for springtails?
“At a slurry volume that corresponds to normal surface application, the springtails were a little affected. However, it came as a surprise that they actually thrived well also with acidified slurry, even at the high slurry rates,” Bent Tolstrup Christensen says.
“We concluded that with the quantities and the acidification we used in our experiment, there was no negative reaction from the springtails, neither from treated or acidified slurry, compared to springtails in soil without slurry. In fact, in some cases we saw a clear positive reaction to slurry,” Bent Tolstrup Christensen concludes.
For a single species of springtails, the number of individuals was reduced during the trial. It happened at all the different treatments, even for soil without slurry. "Apparently this species did not thrive at all in the experimental set-up that we had chosen here," Bent Tolstrup Christensen explains.
”Effect of acidified cattle slurry on a soil collembolan community: A mesocosmos study” is written by Alessandra D’Annibale, Rodrigo Labouriau, Peter Sørensen, Paul H. Krogh, Bent T. Christensen and Jørgen Eriksen. Available om ScienceDirect. https://www.sciencedirect.com/science/article/pii/S1164556318304667?via%3Dihub
Professor Bent Tolstrup Christensen, Department of Agroecology, Aarhus Universitet. Email: email@example.com. Tel. +45 8715 7764