How do you interpret the word moist

Soil animals like moist

May 22, 2018, topic: Soil ecotoxicology

The bait strip test is a useful way to determine soil quality in the field. The Ecotox Center has examined the influence of soil moisture on the test result in more detail: This makes it easier to interpret the results and brings the test one step closer to routine use.

The bait strip test is a simple functional test that measures the soil quality via the biological feeding activity of soil organisms. The appetite of invertebrates such as earthworms, enchytrae (ground worms), springtails and mites is assessed together. For the test, perforated plastic strips are filled with an organic bait substance, stuck into the ground and the amount of material consumed is measured after a certain period of time. The test can be used directly in the field to assess the effect of pollutants or to monitor the biological soil quality over the long term. Disturbances such as chemical pollution or soil compaction can reduce the feeding activity of soil organisms. But other factors such as soil moisture also influence the feeding activity and make it difficult to interpret the results. So far, however, there is little data on this.

Laboratory test under controlled conditions

To improve the interpretation of the test and make it more useful for users, the Ecotox Center systematically examined the relationship between soil moisture and the feeding rate of springtails, earthworms and enchytrae, all typical soil animals. "In order to be able to assess the different species individually and to be able to control the conditions well, we carried out the tests with a standard floor in the laboratory," explains Gilda Dell’Ambrogio. “We selected the number of animals on the basis of literature data on the density of species in undisturbed arable soils.” In preliminary tests, the springtails showed very little appetite for the bait strips. Therefore, the scientists only used the earthworms and enchytrae in further experiments.

Soil moisture increases the appetite of invertebrates

The animals were placed in sandy loam soil with a volumetric water content between 7 and 47% and incubated with the bait strips for 2 to 12 days. Vessels without soil organisms served as controls. Both animal species eat more substrate with increasing moisture. Their feeding activity increased until it reached an optimum: in earthworms this was 23% of the volumetric water content of the model soil and in enchytrae it was 31%. The earthworms each ate the bait faster than the enchytra. The scientists were able to describe the increase in feeding activity with soil moisture up to the optimum with a linear regression. It showed a similar slope for both organisms. The optimal soil moisture was in the range of the field capacity of a typical field soil. If the moisture content is even higher, the animals will eat less. The enchytrae reacted more sensitively to very wet soils.

The Ecotox Center has successfully used the bait strip test in shooting ranges, vineyards and fields in the past. In addition to its use in the field - the most important application of the method - the bait strip test is also a simple and efficient method to test the feeding activity of soil organisms in the laboratory. With the data obtained, the scientists were able to develop a first model that describes the influence of soil moisture on feeding activity. Using such a model can improve the interpretation of the bait strip test for different soil moisture levels in the field. "Next, we want to examine the influence of soil moisture on different types of soil," explains Gild Dell’Ambrogio. "The soil properties influence both the species composition and the number of soil organisms as well as the soil moisture."