The processing of soil samples for nutrient analysis or for radiologic measurements can be carried out using the Soil Deagglomerator Pulverisette 8 from Fritsch.
Depending on perceptions and scientific discipline, soil can be defined differently.
In geology and in soil science, the term soil is categorised according to DIN 4022 as follows: the fraction of the soil with a diameter of more than 2mm is considered as gravel, which is then divided into coarse, medium and fine gravel; the grain fraction between 0.063mm and 2.0mm is identified as sand, which is differentiated into coarse, medium and fine sand; contents of the soil with equivalence diameter between 0.002mm and 0.063mm are grouped in coarse, medium and fine silt; and elements of the soil smaller than 0.002mm (2um) are considered as clay.
All segments of gravel - the contents of the soil larger than 2mm - are not available as nutrients for plants and also do not bond nutrients.
Gravel is also referred to as coarse soil.
All soil contents with an equivalence diameter of 2mm and smaller, however, deliver nutrients for the plants themselves or bind nutrients for the plants, for example, in the form of added fertiliser.
This type of fraction is considered as fine soil.
For the preparation of agricultural soil samples for the analysis of nutrients, the VDLUFA demands in the book of methods Volume 1 'Analysis of soils' the separation of coarse and fine soil.
For examinations of radioactivity in the environment, the pre-treatment of the sample is described in DIN ISO 18589-2, radioactivity in the environment - soil part 2.
Also, for examination of past polluted areas, the Federal Soil Protection and Past Contaminated Area Ordinance assumes a separation at 2mm.
This results in the sieving off and deagglomeration of soil samples of 2mm.
During the preparation of soil samples, the shares of the coarse soil may not be comminuted because they would then be considered as part of the fine soil, which would reveal a 'dilution' of the contents of the fine soil.
The results would be low analysis values of the nutrients and harmful substances - but still, agglomerates from fine contents have to be crushed in order to be driven through a 2mm sieve.
For this task Fritsch developed the Soil Deagglomerator Pulverisette 8.
The design of the Fritsch Soil Deagglomerator Pulverisette 8 is claimed to guarantee with almost all soil samples that the agglomerates, which are almost rock hard, can be opened up and that the coarse soil will not be comminuted.
The rocks are collected in a separate collection vessel.
This may become problematic with highly binding soils or soils with a large share of rocks; the large rocks should be sorted out.
High-binding soils while damp should be spread out and then air dried.
Despite these measures, should all agglomerates not have been crushed, the samples may have to be prepared or reworked.
In the Fritsch example, a wooden hammer was used.
In any case, no particles larger than 2mm should be comminuted, which would therefore distort the sample.
For chemical analysis, a sample of analytical fineness is mandatory.
Generally, this is a fineness of 95 per cent less than 63um.
For this Fritsch recommends the planetary mill Pulverisette 6 classic line equipped with a 250ml agate grinding bowl and six agate grinding balls with a diameter of 30mm.
Since the bowl features approximately 100g of useful capacity, a representative sample amount can be prepared.
From agate, the only abrasion could be silicone oxide.
Depending on the on the soil conditions the comminution time is approximately two to five minutes.
