Processing soil samples for nutrient analysis

What is soil?

Soil is the loose covering the earth's topmost surface, which is practically always active.

Downwards the soil is bordered by solid or loose rocks. towards the top it is mostly bordered by a cover of vegetation, as well as atmosphere. Where the topmost layer of soil is covered by water, lakes, rivers and oceans it is considered sediment rather than soil can be defined differently.

Term of soil catogorised according to DIN 4022

Gravel - the fraction of the soil with diameter <2mm is considered as gravel, which again is divided into coarse, medium and fine gravel.

Sand- The grain fraction between 0.063mm and 2.0mm is identified as sand, which again is differentiated into coarse, medium and fine sand.

Coarse clay or silt - Contents of the soil equivalence diameter between 0.002mm and 0.063mm are grouped in coarse, medium and fine silt. The cohosive soil layer is referred in general terms also as clay.

Clay- Elements of the soil smaller than 0.002mm are considered as clay.

Soil and nutrient

Scientifically it is proven, that 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. It also referred to as coarse soil. ALl soil contents with on 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 fraction is considered as fine soil


Preparing soil samples

For preparation of agricultural soil samples for the analysis of nutrients, the VDLUFA demands in the book of methods volume 1 "analysis of soils" the seperation of coarse and fine soil.

for examination of radioactivity in the environment, the pre-treatment of the sample is described in DIN ISO 18589-2 radioactivity in 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.