Lysimeter

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Large lysimeter system in Neuenkirchen / St. Arnold on the Münsterländer gravel sand train
Lysimeter station in Kittendorf from the State Office for Environment and Nature Neubrandenburg

A lysimeter (from the Greek lysis = solution, dissolution and metron = measure) is a device for determining the soil water balance (seepage rate, evaporation) and for sampling soil seepage water to determine its quantity and quality. In environmental research and agriculture, lysimeters are used to record the interactions or the transport of substances between the atmosphere, plants, soil , fauna and groundwater .

functionality

How a lysimeter station works

Lysimeters are open-topped cylinders that are filled with a soil core and embedded in the soil in such a way that they are flush with their surroundings. The cylinder is closed at the lower end. The seepage water is collected at the bottom of the cylinder and fed to a measuring device. The soil in the lysimeter is usually an undisturbed soil core from the surrounding area, but can also be a disturbed, artificially layered soil in the case of special issues. The surface of the soil core in the lysimeter is mostly covered with vegetation in the immediate vicinity.

Facility

View into the shaft in which the water samples are collected from the open cylinders

When setting up a lysimeter, it should be noted that the installation measures represent a significant disruption of the natural material and water balance (joint between cylinder and soil core, vegetation, etc.) and that it usually takes a long time (up to one or two years) to an equilibrium has been restored and the lysimeter has adapted to its surroundings. Only then can usable measurement results be achieved.

Lysimeter types

A distinction is made between large and small lysimeters. Large lysimeters are expensive structures made of metal (lysimeter cylinder) or concrete (basins, e.g. with natural forest vegetation). The lysimeter cylinders have a diameter of up to 3.2 m and a height of up to 3 m. Some of the lysimeters are on scales (weighable lysimeters) and can be accessed underground for checking and sampling (lysimeter cellar).

Small lysimeters have a diameter of around 10–30 cm (e.g. made of metal or ceramic) and the base core heights are around 10–30 cm, depending on the issue. Together with the container for the seepage water, they can be removed from the ground from above and weighed or sampled.

Snow lysimeters usually have a diameter of 1.60 meters and are used exclusively to determine the current snow rate.

The Academy of Agricultural Sciences of the GDR operated a lysimeter system of approx. 100 m × 100 m north of Weimar (Ramsla / Buttelstedt). This enabled the water balance of cereal or potato fields to be monitored over the long term. The measuring station installed at the end of the stroke belongs to the Thuringian State Institute for Agriculture in neighboring Jena.

Measurands

A lysimeter can be used to measure the water balance and material balance of the soil and plants ( plant coefficient ). The amount of seepage water (infiltration) can be measured directly by collecting it or determined from the weight of the lysimeter. The difference between the amount of precipitation and the amount of seepage water is evaporation ( evaporation or evapotranspiration ). The chemical analysis of the seepage water provides information on the substance balance (nutrients, pollutants, etc.).

application areas

Meteorologists use weighable lysimeters to determine evaporation. Small lysimeters are used in environmental research to track the migration of pollutants from the soil surface into the soil (e.g. pollutants introduced via deposition ). There are only a few large lysimeter systems in Germany. In environmental research and agriculture, large lysimeters reproduce a section of the soil in which interactions or the transport of substances between the atmosphere, plants, soil, fauna and groundwater can be studied in detail under natural conditions. Among other things, lysimeters are used to answer questions related to global warming . Lysimeters are also used in the chemical industry for the development of pesticides, because data on the behavior of the pesticides (migration, degradation, metabolites, etc.) must be submitted for approval.

literature

  • Heinz Haushofer: The invention of the lysimeter . In: Zeitschrift für Agrargeschichte und Agrarsoziologie 10, 1962, pp. 57-60, ISSN  0044-2194 .

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