EUF soil survey

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The soil analysis according to the EUF method (electro-ultrafiltration) is a laboratory analysis method for the analysis of soil substrates for their nutrients available for plants .

The EUF method is a practical fertilizer advice system from drawing the soil sample to making a fertilizer recommendation.

Explanation

Basically, the EUF soil investigation describes a process with which nutrients are extracted from the soil . In contrast to other extraction processes , the EUF method uses fully demineralized water (VE) as the extraction agent, which means that there are no interfering foreign ions. This allows all water-soluble nutrients contained in the soil to be recorded directly. The subsequent chemical determination of the elements and compounds, as well as their concentration, is carried out with conventional analysis from the extraction solution (atomic spectroscopy or spectrophotometry).

method

The principle of the EUF method consists of an extraction of nutrients from the soil substrate supported by water (as a transport medium), tension, temperature and negative pressure. The extraction is carried out in a unit specially developed for this process (see figure).

EUF chamber system

Five grams of soil are weighed into the center piece of the EUF chamber system and filled with fully demineralized water (soil to water ratio = 1:50). A sensor keeps the water level constant, while the heater, temperature probe and agitator ensure homogeneous physical conditions in the middle section. This is separated from the outer chambers by ultrafilter and platinum grid electrodes . The grid electrodes serve as anode or cathode .

The method allows different fractions to be obtained by varying the extraction conditions . It is thus possible to record soluble nutrients (first fraction) under "gentle" extraction conditions and the nutrients that can be supplied in the soil under "harder" conditions (second fraction). In principle, any number of fractions can be created, with which the release of nutrients can be reproduced ( desorption curves ). This enables statements to be made about the dynamics over time and thus about the release kinetics of the substances in the soil. The following fractions are currently being determined for practice:

In the first fraction, the following conditions apply for 30 minutes:

  • 20 ° C
  • maximum 200 volts
  • maximum 15 milliamps (mA)

In the second faction, the following conditions apply for five minutes:

  • 80 ° C
  • maximum 400 volts
  • maximum 150 milliamps (mA)

During the entire extraction time, the negative pressure is −0.7 bar in the anode chamber and −0.3 bar in the cathode chamber.

The filtrate, which is collected separately for each fraction, collects in the chambers below the anode or cathode. These filtrates are each separately submitted for chemical analysis .

Analysis spectrum

At the present time, all of the main nutrients of the plants are examined simultaneously from a soil sample. In addition to nitrogen (in the form of nitrate , ammonium and easily soluble, organically bound nitrogen ), phosphorus , potassium and calcium , sodium , magnesium , sulfur and boron are analyzed. The EUF method allows the extraction of all water-soluble ions , only the analytical detectability is limiting.

The EUF fertilizer advice model

From the drawing of the soil sample to the creation of a fertilizer recommendation specific to the field and crop type, the EUF soil analysis is a model that, compared to other soil analyzes, is characterized by its high level of practicability:

  • The soil sample is only taken from the plow furrow (0-30 cm).
  • Sampling takes place when there are stable nutrient conditions in the soil, i. H. when the previous crop has stopped absorbing nutrients (shortly before the grain harvest or in November in the year before the crop for which the fertilizer recommendation is to be made).
  • No cold chain is required for the soil sample .
  • Only a single extraction is necessary for all nutrients.

literature

  • Németh, K. (1979): The availability of nutrients in the soil as determined by electroultrafiltration (EUF) . Adv. Agronomy 31 , 155-188
  • Németh, K. (1985): Recent advances in EUF research (1980-1983) . Plant and Soil 83 , 1-19
  • Mengel, K. and Kirkby, EA (2001): Principles of Plant Nutrition . Kluwer Academic Publishers, Bern 2001, ISBN 1402000081